CloudFlare suffered a massive security issue affecting all of its customers, including Rosetta Code. All passwords not changed since February 19th 2017 have been expired, and session cookie longevity will be reduced until late March.--Michael Mol (talk) 05:15, 25 February 2017 (UTC)

# Sutherland-Hodgman polygon clipping

Sutherland-Hodgman polygon clipping
You are encouraged to solve this task according to the task description, using any language you may know.

The   Sutherland-Hodgman clipping algorithm   finds the polygon that is the intersection between an arbitrary polygon (the “subject polygon”) and a convex polygon (the “clip polygon”).

It is used in computer graphics (especially 2D graphics) to reduce the complexity of a scene being displayed by eliminating parts of a polygon that do not need to be displayed.

Take the closed polygon defined by the points:

${\displaystyle [(50,150),(200,50),(350,150),(350,300),(250,300),(200,250),(150,350),(100,250),(100,200)]}$

and clip it by the rectangle defined by the points:

${\displaystyle [(100,100),(300,100),(300,300),(100,300)]}$

Print the sequence of points that define the resulting clipped polygon.

Extra credit

Display all three polygons on a graphical surface, using a different color for each polygon and filling the resulting polygon.

(When displaying you may use either a north-west or a south-west origin, whichever is more convenient for your display mechanism.)

## Contents

`with Ada.Containers.Doubly_Linked_Lists;with Ada.Text_IO; procedure Main is   package FIO is new Ada.Text_IO.Float_IO (Float);    type Point is record      X, Y : Float;   end record;    function "-" (Left, Right : Point) return Point is   begin      return (Left.X - Right.X, Left.Y - Right.Y);   end "-";    type Edge is array (1 .. 2) of Point;    package Point_Lists is new Ada.Containers.Doubly_Linked_Lists     (Element_Type => Point);   use type Point_Lists.List;   subtype Polygon is Point_Lists.List;    function Inside (P : Point; E : Edge) return Boolean is   begin      return (E (2).X - E (1).X) * (P.Y - E (1).Y) >             (E (2).Y - E (1).Y) * (P.X - E (1).X);   end Inside;    function Intersecton (P1, P2 : Point; E : Edge) return Point is      DE : Point := E (1) - E (2);      DP : Point := P1 - P2;      N1 : Float := E (1).X * E (2).Y - E (1).Y * E (2).X;      N2 : Float := P1.X * P2.Y - P1.Y * P2.X;      N3 : Float := 1.0 / (DE.X * DP.Y - DE.Y * DP.X);   begin      return ((N1 * DP.X - N2 * DE.X) * N3, (N1 * DP.Y - N2 * DE.Y) * N3);   end Intersecton;    function Clip (P, C : Polygon) return Polygon is      use Point_Lists;      A, B, S, E : Cursor;      Inputlist  : List;      Outputlist : List := P;      AB         : Edge;   begin      A := C.First;      B := C.Last;      while A /= No_Element loop         AB        := (Element (B), Element (A));         Inputlist := Outputlist;         Outputlist.Clear;         S := Inputlist.Last;         E := Inputlist.First;         while E /= No_Element loop            if Inside (Element (E), AB) then               if not Inside (Element (S), AB) then                  Outputlist.Append                    (Intersecton (Element (S), Element (E), AB));               end if;               Outputlist.Append (Element (E));            elsif Inside (Element (S), AB) then               Outputlist.Append                 (Intersecton (Element (S), Element (E), AB));            end if;            S := E;            E := Next (E);         end loop;         B := A;         A := Next (A);      end loop;      return Outputlist;   end Clip;    procedure Print (P : Polygon) is      use Point_Lists;      C : Cursor := P.First;   begin      Ada.Text_IO.Put_Line ("{");      while C /= No_Element loop         Ada.Text_IO.Put (" (");         FIO.Put (Element (C).X, Exp => 0);         Ada.Text_IO.Put (',');         FIO.Put (Element (C).Y, Exp => 0);         Ada.Text_IO.Put (')');         C := Next (C);         if C /= No_Element then            Ada.Text_IO.Put (',');         end if;         Ada.Text_IO.New_Line;      end loop;      Ada.Text_IO.Put_Line ("}");   end Print;    Source  : Polygon;   Clipper : Polygon;   Result  : Polygon;begin   Source.Append ((50.0, 150.0));   Source.Append ((200.0, 50.0));   Source.Append ((350.0, 150.0));   Source.Append ((350.0, 300.0));   Source.Append ((250.0, 300.0));   Source.Append ((200.0, 250.0));   Source.Append ((150.0, 350.0));   Source.Append ((100.0, 250.0));   Source.Append ((100.0, 200.0));   Clipper.Append ((100.0, 100.0));   Clipper.Append ((300.0, 100.0));   Clipper.Append ((300.0, 300.0));   Clipper.Append ((100.0, 300.0));   Result := Clip (Source, Clipper);   Print (Result);end Main;`
Output:
```{
(100.00000,116.66667),
(125.00000,100.00000),
(275.00000,100.00000),
(300.00000,116.66667),
(300.00000,300.00000),
(250.00000,300.00000),
(200.00000,250.00000),
(175.00000,300.00000),
(125.00000,300.00000),
(100.00000,250.00000)
}```

## BBC BASIC

`      VDU 23,22,200;200;8,16,16,128      VDU 23,23,2;0;0;0;       DIM SubjPoly{(8) x, y}      DIM ClipPoly{(3) x, y}      FOR v% = 0 TO 8 : READ SubjPoly{(v%)}.x, SubjPoly{(v%)}.y : NEXT      DATA 50,150,200,50,350,150,350,300,250,300,200,250,150,350,100,250,100,200      FOR v% = 0 TO 3 : READ ClipPoly{(v%)}.x, ClipPoly{(v%)}.y : NEXT      DATA 100,100, 300,100, 300,300, 100,300       GCOL 4 : PROCplotpoly(SubjPoly{()}, 9)      GCOL 1 : PROCplotpoly(ClipPoly{()}, 4)      nvert% = FNsutherland_hodgman(SubjPoly{()}, ClipPoly{()}, Clipped{()})      GCOL 2 : PROCplotpoly(Clipped{()}, nvert%)      END       DEF FNsutherland_hodgman(subj{()}, clip{()}, RETURN out{()})      LOCAL i%, j%, n%, o%, p1{}, p2{}, s{}, e{}, p{}, inp{()}      DIM p1{x,y}, p2{x,y}, s{x,y}, e{x,y}, p{x,y}      n% = DIM(subj{()},1) + DIM(clip{()},1)      DIM inp{(n%) x, y}, out{(n%) x,y}      FOR o% = 0 TO DIM(subj{()},1) : out{(o%)} = subj{(o%)} : NEXT      p1{} = clip{(DIM(clip{()},1))}      FOR i% = 0 TO DIM(clip{()},1)        p2{} = clip{(i%)}        FOR n% = 0 TO o% - 1 : inp{(n%)} = out{(n%)} : NEXT : o% = 0        IF n% >= 2 THEN          s{} = inp{(n% - 1)}          FOR j% = 0 TO n% - 1            e{} = inp{(j%)}            IF FNside(e{}, p1{}, p2{}) THEN              IF NOT FNside(s{}, p1{}, p2{}) THEN                PROCintersection(p1{}, p2{}, s{}, e{}, p{})                out{(o%)} = p{}                o% += 1              ENDIF              out{(o%)} = e{}              o% += 1            ELSE              IF FNside(s{}, p1{}, p2{}) THEN                PROCintersection(p1{}, p2{}, s{}, e{}, p{})                out{(o%)} = p{}                o% += 1              ENDIF            ENDIF            s{} = e{}          NEXT        ENDIF        p1{} = p2{}      NEXT i%      = o%       REM Which side of the line p1-p2 is the point p?      DEF FNside(p{}, p1{}, p2{})      =  (p2.x - p1.x) * (p.y - p1.y) > (p2.y - p1.y) * (p.x - p1.x)       REM Find the intersection of two lines p1-p2 and p3-p4      DEF PROCintersection(p1{}, p2{}, p3{}, p4{}, p{})      LOCAL a{}, b{}, k, l, m : DIM a{x,y}, b{x,y}      a.x = p1.x - p2.x : a.y = p1.y - p2.y      b.x = p3.x - p4.x : b.y = p3.y - p4.y      k = p1.x * p2.y - p1.y * p2.x      l = p3.x * p4.y - p3.y * p4.x      m = 1 / (a.x * b.y - a.y * b.x)      p.x =  m * (k * b.x - l * a.x)      p.y =  m * (k * b.y - l * a.y)      ENDPROC       REM plot a polygon      DEF PROCplotpoly(poly{()}, n%)      LOCAL i%      MOVE poly{(0)}.x, poly{(0)}.y      FOR i% = 1 TO n%-1        DRAW poly{(i%)}.x, poly{(i%)}.y      NEXT      DRAW poly{(0)}.x, poly{(0)}.y      ENDPROC`

## C

Most of the code is actually storage util routines, such is C. Prints out nodes, and writes test.eps file in current dir.

`#include <stdio.h>#include <stdlib.h>#include <math.h> typedef struct { double x, y; } vec_t, *vec; inline double dot(vec a, vec b){	return a->x * b->x + a->y * b->y;} inline double cross(vec a, vec b){	return a->x * b->y - a->y * b->x;} inline vec vsub(vec a, vec b, vec res){	res->x = a->x - b->x;	res->y = a->y - b->y;	return res;} /* tells if vec c lies on the left side of directed edge a->b * 1 if left, -1 if right, 0 if colinear */int left_of(vec a, vec b, vec c){	vec_t tmp1, tmp2;	double x;	vsub(b, a, &tmp1);	vsub(c, b, &tmp2);	x = cross(&tmp1, &tmp2);	return x < 0 ? -1 : x > 0;} int line_sect(vec x0, vec x1, vec y0, vec y1, vec res){	vec_t dx, dy, d;	vsub(x1, x0, &dx);	vsub(y1, y0, &dy);	vsub(x0, y0, &d);	/* x0 + a dx = y0 + b dy ->	   x0 X dx = y0 X dx + b dy X dx ->	   b = (x0 - y0) X dx / (dy X dx) */	double dyx = cross(&dy, &dx);	if (!dyx) return 0;	dyx = cross(&d, &dx) / dyx;	if (dyx <= 0 || dyx >= 1) return 0; 	res->x = y0->x + dyx * dy.x;	res->y = y0->y + dyx * dy.y;	return 1;} /* === polygon stuff === */typedef struct { int len, alloc; vec v; } poly_t, *poly; poly poly_new(){	return (poly)calloc(1, sizeof(poly_t));} void poly_free(poly p){	free(p->v);	free(p);} void poly_append(poly p, vec v){	if (p->len >= p->alloc) {		p->alloc *= 2;		if (!p->alloc) p->alloc = 4;		p->v = (vec)realloc(p->v, sizeof(vec_t) * p->alloc);	}	p->v[p->len++] = *v;} /* this works only if all of the following are true: *   1. poly has no colinear edges; *   2. poly has no duplicate vertices; *   3. poly has at least three vertices; *   4. poly is convex (implying 3).*/int poly_winding(poly p){	return left_of(p->v, p->v + 1, p->v + 2);} void poly_edge_clip(poly sub, vec x0, vec x1, int left, poly res){	int i, side0, side1;	vec_t tmp;	vec v0 = sub->v + sub->len - 1, v1;	res->len = 0; 	side0 = left_of(x0, x1, v0);	if (side0 != -left) poly_append(res, v0); 	for (i = 0; i < sub->len; i++) {		v1 = sub->v + i;		side1 = left_of(x0, x1, v1);		if (side0 + side1 == 0 && side0)			/* last point and current straddle the edge */			if (line_sect(x0, x1, v0, v1, &tmp))				poly_append(res, &tmp);		if (i == sub->len - 1) break;		if (side1 != -left) poly_append(res, v1);		v0 = v1;		side0 = side1;	}} poly poly_clip(poly sub, poly clip){	int i;	poly p1 = poly_new(), p2 = poly_new(), tmp; 	int dir = poly_winding(clip);	poly_edge_clip(sub, clip->v + clip->len - 1, clip->v, dir, p2);	for (i = 0; i < clip->len - 1; i++) {		tmp = p2; p2 = p1; p1 = tmp;		if(p1->len == 0) {			p2->len = 0;			break;		}		poly_edge_clip(p1, clip->v + i, clip->v + i + 1, dir, p2);	} 	poly_free(p1);	return p2;} int main(){	int i;	vec_t c[] = {{100,100}, {300,100}, {300,300}, {100,300}};	//vec_t c[] = {{100,300}, {300,300}, {300,100}, {100,100}};	vec_t s[] = {	{50,150}, {200,50}, {350,150},			{350,300},{250,300},{200,250},			{150,350},{100,250},{100,200}};#define clen (sizeof(c)/sizeof(vec_t))#define slen (sizeof(s)/sizeof(vec_t))	poly_t clipper = {clen, 0, c};	poly_t subject = {slen, 0, s}; 	poly res = poly_clip(&subject, &clipper); 	for (i = 0; i < res->len; i++)		printf("%g %g\n", res->v[i].x, res->v[i].y); 	/* long and arduous EPS printout */	FILE * eps = fopen("test.eps", "w");	fprintf(eps, "%%!PS-Adobe-3.0\n%%%%BoundingBox: 40 40 360 360\n"		"/l {lineto} def /m{moveto} def /s{setrgbcolor} def"		"/c {closepath} def /gs {fill grestore stroke} def\n");	fprintf(eps, "0 setlinewidth %g %g m ", c[0].x, c[0].y);	for (i = 1; i < clen; i++)		fprintf(eps, "%g %g l ", c[i].x, c[i].y);	fprintf(eps, "c .5 0 0 s gsave 1 .7 .7 s gs\n"); 	fprintf(eps, "%g %g m ", s[0].x, s[0].y);	for (i = 1; i < slen; i++)		fprintf(eps, "%g %g l ", s[i].x, s[i].y);	fprintf(eps, "c 0 .2 .5 s gsave .4 .7 1 s gs\n"); 	fprintf(eps, "2 setlinewidth [10 8] 0 setdash %g %g m ",		res->v[0].x, res->v[0].y);	for (i = 1; i < res->len; i++)		fprintf(eps, "%g %g l ", res->v[i].x, res->v[i].y);	fprintf(eps, "c .5 0 .5 s gsave .7 .3 .8 s gs\n"); 	fprintf(eps, "%%%%EOF");	fclose(eps);	printf("test.eps written\n"); 	return 0;}`
Output:
```200 250
175 300
125 300
100 250
100 200
100 116.667
125 100
275 100
300 116.667
300 300
250 300

test.eps written```

## C#

This was written in .net 4.0 using wpf

Worker class:

`using System;using System.Collections.Generic;using System.Linq;using System.Text;using System.Windows; namespace Sutherland{    public static class SutherlandHodgman    {        #region Class: Edge         /// <summary>        /// This represents a line segment        /// </summary>        private class Edge        {            public Edge(Point from, Point to)            {                this.From = from;                this.To = to;            }             public readonly Point From;            public readonly Point To;        }         #endregion         /// <summary>        /// This clips the subject polygon against the clip polygon (gets the intersection of the two polygons)        /// </summary>        /// <remarks>        /// Based on the psuedocode from:        /// http://en.wikipedia.org/wiki/Sutherland%E2%80%93Hodgman        /// </remarks>        /// <param name="subjectPoly">Can be concave or convex</param>        /// <param name="clipPoly">Must be convex</param>        /// <returns>The intersection of the two polygons (or null)</returns>        public static Point[] GetIntersectedPolygon(Point[] subjectPoly, Point[] clipPoly)        {            if (subjectPoly.Length < 3 || clipPoly.Length < 3)            {                throw new ArgumentException(string.Format("The polygons passed in must have at least 3 points: subject={0}, clip={1}", subjectPoly.Length.ToString(), clipPoly.Length.ToString()));            }             List<Point> outputList = subjectPoly.ToList();             //	Make sure it's clockwise            if (!IsClockwise(subjectPoly))            {                outputList.Reverse();            }             //	Walk around the clip polygon clockwise            foreach (Edge clipEdge in IterateEdgesClockwise(clipPoly))            {                List<Point> inputList = outputList.ToList();		//	clone it                outputList.Clear();                 if (inputList.Count == 0)                {                    //	Sometimes when the polygons don't intersect, this list goes to zero.  Jump out to avoid an index out of range exception                    break;                }                 Point S = inputList[inputList.Count - 1];                 foreach (Point E in inputList)                {                    if (IsInside(clipEdge, E))                    {                        if (!IsInside(clipEdge, S))                        {                            Point? point = GetIntersect(S, E, clipEdge.From, clipEdge.To);                            if (point == null)                            {                                throw new ApplicationException("Line segments don't intersect");		//	may be colinear, or may be a bug                            }                            else                            {                                outputList.Add(point.Value);                            }                        }                         outputList.Add(E);                    }                    else if (IsInside(clipEdge, S))                    {                        Point? point = GetIntersect(S, E, clipEdge.From, clipEdge.To);                        if (point == null)                        {                            throw new ApplicationException("Line segments don't intersect");		//	may be colinear, or may be a bug                        }                        else                        {                            outputList.Add(point.Value);                        }                    }                     S = E;                }            }             //	Exit Function            return outputList.ToArray();        }         #region Private Methods         /// <summary>        /// This iterates through the edges of the polygon, always clockwise        /// </summary>        private static IEnumerable<Edge> IterateEdgesClockwise(Point[] polygon)        {            if (IsClockwise(polygon))            {                #region Already clockwise                 for (int cntr = 0; cntr < polygon.Length - 1; cntr++)                {                    yield return new Edge(polygon[cntr], polygon[cntr + 1]);                }                 yield return new Edge(polygon[polygon.Length - 1], polygon[0]);                 #endregion            }            else            {                #region Reverse                 for (int cntr = polygon.Length - 1; cntr > 0; cntr--)                {                    yield return new Edge(polygon[cntr], polygon[cntr - 1]);                }                 yield return new Edge(polygon[0], polygon[polygon.Length - 1]);                 #endregion            }        }         /// <summary>        /// Returns the intersection of the two lines (line segments are passed in, but they are treated like infinite lines)        /// </summary>        /// <remarks>        /// Got this here:        /// http://stackoverflow.com/questions/14480124/how-do-i-detect-triangle-and-rectangle-intersection        /// </remarks>        private static Point? GetIntersect(Point line1From, Point line1To, Point line2From, Point line2To)        {            Vector direction1 = line1To - line1From;            Vector direction2 = line2To - line2From;            double dotPerp = (direction1.X * direction2.Y) - (direction1.Y * direction2.X);             // If it's 0, it means the lines are parallel so have infinite intersection points            if (IsNearZero(dotPerp))            {                return null;            }             Vector c = line2From - line1From;            double t = (c.X * direction2.Y - c.Y * direction2.X) / dotPerp;            //if (t < 0 || t > 1)            //{            //    return null;		//	lies outside the line segment            //}             //double u = (c.X * direction1.Y - c.Y * direction1.X) / dotPerp;            //if (u < 0 || u > 1)            //{            //    return null;		//	lies outside the line segment            //}             //	Return the intersection point            return line1From + (t * direction1);        }         private static bool IsInside(Edge edge, Point test)        {            bool? isLeft = IsLeftOf(edge, test);            if (isLeft == null)            {                //	Colinear points should be considered inside                return true;            }             return !isLeft.Value;        }        private static bool IsClockwise(Point[] polygon)        {            for (int cntr = 2; cntr < polygon.Length; cntr++)            {                bool? isLeft = IsLeftOf(new Edge(polygon[0], polygon[1]), polygon[cntr]);                if (isLeft != null)		//	some of the points may be colinear.  That's ok as long as the overall is a polygon                {                    return !isLeft.Value;                }            }             throw new ArgumentException("All the points in the polygon are colinear");        }         /// <summary>        /// Tells if the test point lies on the left side of the edge line        /// </summary>        private static bool? IsLeftOf(Edge edge, Point test)        {            Vector tmp1 = edge.To - edge.From;            Vector tmp2 = test - edge.To;             double x = (tmp1.X * tmp2.Y) - (tmp1.Y * tmp2.X);		//	dot product of perpendicular?             if (x < 0)            {                return false;            }            else if (x > 0)            {                return true;            }            else            {                //	Colinear points;                return null;            }        }         private static bool IsNearZero(double testValue)        {            return Math.Abs(testValue) <= .000000001d;        }         #endregion    }}`

Window code:

` <Window x:Class="Sutherland.MainWindow"        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"        Title="Sutherland Hodgman" Background="#B0B0B0" ResizeMode="CanResizeWithGrip" Width="525" Height="450">    <Grid Margin="4">        <Grid.RowDefinitions>            <RowDefinition Height="1*"/>            <RowDefinition Height="auto"/>        </Grid.RowDefinitions>         <Border Grid.Row="0" CornerRadius="4" BorderBrush="#707070" Background="#FFFFFF" BorderThickness="2">            <Canvas Name="canvas"/>        </Border>         <UniformGrid Grid.Row="1" Rows="1" Margin="0,4,0,0">            <Button Name="btnTriRect" Content="Triangle - Rectangle" Margin="4,0" Click="btnTriRect_Click"/>            <Button Name="btnConvex" Content="Concave - Convex" Click="btnConvex_Click"/>        </UniformGrid>    </Grid></Window> `
`using System;using System.Collections.Generic;using System.Linq;using System.Text;using System.Windows;using System.Windows.Controls;using System.Windows.Data;using System.Windows.Documents;using System.Windows.Input;using System.Windows.Media;using System.Windows.Media.Imaging;using System.Windows.Navigation;using System.Windows.Shapes; namespace Sutherland{    public partial class MainWindow : Window    {        #region Declaration Section         private Random _rand = new Random();         private Brush _subjectBack = new SolidColorBrush(ColorFromHex("30427FCF"));        private Brush _subjectBorder = new SolidColorBrush(ColorFromHex("427FCF"));        private Brush _clipBack = new SolidColorBrush(ColorFromHex("30D65151"));        private Brush _clipBorder = new SolidColorBrush(ColorFromHex("D65151"));        private Brush _intersectBack = new SolidColorBrush(ColorFromHex("609F18CC"));        private Brush _intersectBorder = new SolidColorBrush(ColorFromHex("9F18CC"));         #endregion         #region Constructor         public MainWindow()        {            InitializeComponent();        }         #endregion         #region Event Listeners         private void btnTriRect_Click(object sender, RoutedEventArgs e)        {            try            {                double width = canvas.ActualWidth;                double height = canvas.ActualHeight;                 Point[] poly1 = new Point[] {				    new Point(_rand.NextDouble() * width, _rand.NextDouble() * height),				    new Point(_rand.NextDouble() * width, _rand.NextDouble() * height),				    new Point(_rand.NextDouble() * width, _rand.NextDouble() * height) };                 Point rectPoint = new Point(_rand.NextDouble() * (width * .75d), _rand.NextDouble() * (height * .75d));		//	don't let it start all the way at the bottom right                Rect rect = new Rect(                    rectPoint,                    new Size(_rand.NextDouble() * (width - rectPoint.X), _rand.NextDouble() * (height - rectPoint.Y)));                 Point[] poly2 = new Point[] { rect.TopLeft, rect.TopRight, rect.BottomRight, rect.BottomLeft };                 Point[] intersect = SutherlandHodgman.GetIntersectedPolygon(poly1, poly2);                 canvas.Children.Clear();                ShowPolygon(poly1, _subjectBack, _subjectBorder, 1d);                ShowPolygon(poly2, _clipBack, _clipBorder, 1d);                ShowPolygon(intersect, _intersectBack, _intersectBorder, 3d);            }            catch (Exception ex)            {                MessageBox.Show(ex.ToString(), this.Title, MessageBoxButton.OK, MessageBoxImage.Error);            }        }        private void btnConvex_Click(object sender, RoutedEventArgs e)        {            try            {                Point[] poly1 = new Point[] { new Point(50, 150), new Point(200, 50), new Point(350, 150), new Point(350, 300), new Point(250, 300), new Point(200, 250), new Point(150, 350), new Point(100, 250), new Point(100, 200) };                Point[] poly2 = new Point[] { new Point(100, 100), new Point(300, 100), new Point(300, 300), new Point(100, 300) };                 Point[] intersect = SutherlandHodgman.GetIntersectedPolygon(poly1, poly2);                 canvas.Children.Clear();                ShowPolygon(poly1, _subjectBack, _subjectBorder, 1d);                ShowPolygon(poly2, _clipBack, _clipBorder, 1d);                ShowPolygon(intersect, _intersectBack, _intersectBorder, 3d);            }            catch (Exception ex)            {                MessageBox.Show(ex.ToString(), this.Title, MessageBoxButton.OK, MessageBoxImage.Error);            }        }         #endregion         #region Private Methods         private void ShowPolygon(Point[] points, Brush background, Brush border, double thickness)        {            if (points == null || points.Length == 0)            {                return;            }             Polygon polygon = new Polygon();            polygon.Fill = background;            polygon.Stroke = border;            polygon.StrokeThickness = thickness;             foreach (Point point in points)            {                polygon.Points.Add(point);            }             canvas.Children.Add(polygon);        }         /// <summary>        /// This is just a wrapper to the color converter (why can't they have a method off the color class with all        /// the others?)        /// </summary>        private static Color ColorFromHex(string hexValue)        {            if (hexValue.StartsWith("#"))            {                return (Color)ColorConverter.ConvertFromString(hexValue);            }            else            {                return (Color)ColorConverter.ConvertFromString("#" + hexValue);            }        }         #endregion    }}`

## D

`import std.stdio, std.array, std.range, std.typecons, std.algorithm; struct Vec2 { // To be replaced with Phobos code.    double x, y;     Vec2 opBinary(string op="-")(in Vec2 other)    const pure nothrow @safe @nogc {        return Vec2(this.x - other.x, this.y - other.y);    }     typeof(x) cross(in Vec2 other) const pure nothrow @safe @nogc {        return this.x * other.y - this.y * other.x;    }} immutable(Vec2)[] clip(in Vec2[] subjectPolygon, in Vec2[] clipPolygon)pure /*nothrow*/ @safe in {    assert(subjectPolygon.length > 1);    assert(clipPolygon.length > 1);    // Probably clipPolygon needs to be convex and probably    // its vertices need to be listed in a direction.} out(result) {    assert(result.length > 1);} body {    alias Edge = Tuple!(Vec2,"p", Vec2,"q");     static enum isInside = (in Vec2 p, in Edge cle)    pure nothrow @safe @nogc =>        (cle.q.x - cle.p.x) * (p.y - cle.p.y) >        (cle.q.y - cle.p.y) * (p.x - cle.p.x);     static Vec2 intersection(in Edge se, in Edge cle)    pure nothrow @safe @nogc {        immutable dc = cle.p - cle.q;        immutable dp = se.p - se.q;        immutable n1 = cle.p.cross(cle.q);        immutable n2 = se.p.cross(se.q);        immutable n3 = 1.0 / dc.cross(dp);        return Vec2((n1 * dp.x - n2 * dc.x) * n3,                    (n1 * dp.y - n2 * dc.y) * n3);    }     // How much slower is this compared to lower-level code?    static enum edges = (in Vec2[] poly) pure nothrow @safe @nogc =>        // poly[\$ - 1 .. \$].chain(poly).zip!Edge(poly);        poly[\$ - 1 .. \$].chain(poly).zip(poly).map!Edge;     immutable(Vec2)[] result = subjectPolygon.idup; // Not nothrow.     foreach (immutable clipEdge; edges(clipPolygon)) {        immutable inputList = result;        result.destroy;        foreach (immutable inEdge; edges(inputList)) {            if (isInside(inEdge.q, clipEdge)) {                if (!isInside(inEdge.p, clipEdge))                    result ~= intersection(inEdge, clipEdge);                result ~= inEdge.q;            } else if (isInside(inEdge.p, clipEdge))                result ~= intersection(inEdge, clipEdge);        }    }     return result;} // Code adapted from the C version.void saveEPSImage(in string fileName, in Vec2[] subjPoly,                  in Vec2[] clipPoly, in Vec2[] clipped)in {    assert(!fileName.empty);    assert(subjPoly.length > 1);    assert(clipPoly.length > 1);    assert(clipped.length > 1);} body {    auto eps = File(fileName, "w");     // The image bounding box is hard-coded, not computed.    eps.writeln("%%!PS-Adobe-3.0%%%%BoundingBox: 40 40 360 360/l {lineto} def/m {moveto} def/s {setrgbcolor} def/c {closepath} def/gs {fill grestore stroke} def");     eps.writef("0 setlinewidth %g %g m ", clipPoly[0].tupleof);    foreach (immutable cl; clipPoly[1 .. \$])        eps.writef("%g %g l ", cl.tupleof);    eps.writefln("c 0.5 0 0 s gsave 1 0.7 0.7 s gs");     eps.writef("%g %g m ", subjPoly[0].tupleof);    foreach (immutable s; subjPoly[1 .. \$])        eps.writef("%g %g l ", s.tupleof);    eps.writefln("c 0 0.2 0.5 s gsave 0.4 0.7 1 s gs");     eps.writef("2 setlinewidth [10 8] 0 setdash %g %g m ",               clipped[0].tupleof);    foreach (immutable c; clipped[1 .. \$])        eps.writef("%g %g l ", c.tupleof);    eps.writefln("c 0.5 0 0.5 s gsave 0.7 0.3 0.8 s gs");     eps.writefln("%%%%EOF");    eps.close;    writeln(fileName, " written.");} void main() {    alias V = Vec2;    immutable subjectPolygon = [V(50, 150), V(200, 50), V(350, 150),                                V(350, 300), V(250, 300), V(200, 250),                                V(150, 350), V(100, 250), V(100, 200)];    immutable clippingPolygon = [V(100, 100), V(300, 100),                                 V(300, 300), V(100, 300)];    immutable clipped = subjectPolygon.clip(clippingPolygon);    writefln("%(%s\n%)", clipped);    saveEPSImage("sutherland_hodgman_clipping_out.eps",                 subjectPolygon, clippingPolygon, clipped);}`
Output:
```immutable(Vec2)(100, 116.667)
immutable(Vec2)(125, 100)
immutable(Vec2)(275, 100)
immutable(Vec2)(300, 116.667)
immutable(Vec2)(300, 300)
immutable(Vec2)(250, 300)
immutable(Vec2)(200, 250)
immutable(Vec2)(175, 300)
immutable(Vec2)(125, 300)
immutable(Vec2)(100, 250)
sutherland_hodgman_clipping_out.eps written.```

It also outputs an EPS file, the same as the C entry.

## Elixir

Translation of: Ruby
`defmodule SutherlandHodgman do  defp inside(cp1, cp2, p), do: (cp2.x-cp1.x)*(p.y-cp1.y) > (cp2.y-cp1.y)*(p.x-cp1.x)   defp intersection(cp1, cp2, s, e) do    {dcx, dcy} = {cp1.x-cp2.x, cp1.y-cp2.y}    {dpx, dpy} = {s.x-e.x, s.y-e.y}    n1 = cp1.x*cp2.y - cp1.y*cp2.x    n2 = s.x*e.y - s.y*e.x    n3 = 1.0 / (dcx*dpy - dcy*dpx)    %{x: (n1*dpx - n2*dcx) * n3, y: (n1*dpy - n2*dcy) * n3}  end   def polygon_clipping(subjectPolygon, clipPolygon) do    Enum.chunk([List.last(clipPolygon) | clipPolygon], 2, 1)    |> Enum.reduce(subjectPolygon, fn [cp1,cp2],acc ->         Enum.chunk([List.last(acc) | acc], 2, 1)         |> Enum.reduce([], fn [s,e],outputList ->              case {inside(cp1, cp2, e), inside(cp1, cp2, s)} do                {true,  true} -> [e | outputList]                {true, false} -> [e, intersection(cp1,cp2,s,e) | outputList]                {false, true} -> [intersection(cp1,cp2,s,e) | outputList]                _             -> outputList              end            end)         |> Enum.reverse       end)  endend subjectPolygon = [[50, 150], [200, 50], [350, 150], [350, 300], [250, 300],                  [200, 250], [150, 350], [100, 250], [100, 200]]                 |> Enum.map(fn [x,y] -> %{x: x, y: y} end) clipPolygon = [[100, 100], [300, 100], [300, 300], [100, 300]]              |> Enum.map(fn [x,y] -> %{x: x, y: y} end) SutherlandHodgman.polygon_clipping(subjectPolygon, clipPolygon)|> Enum.each(&IO.inspect/1)`
Output:
```%{x: 100.0, y: 116.66666666666667}
%{x: 125.00000000000001, y: 100.0}
%{x: 275.0, y: 100.0}
%{x: 300.0, y: 116.66666666666667}
%{x: 300.0, y: 299.99999999999994}
%{x: 250.0, y: 300.0}
%{x: 200, y: 250}
%{x: 175.0, y: 300.0}
%{x: 125.0, y: 300.0}
%{x: 100.0, y: 250.0}
```

## Fortran

Infos: The polygons are fortran type with an allocatable array "vertex" that contains the vertices and an integer n that is the size of the polygon. For any polygon, the first vertex and the last vertex have to be the same. As you will see, in the main function, we allocate the vertex array of the result polygon with its maximal size.

`  module SutherlandHodgmanUtil  ! functions and type needed for Sutherland-Hodgman algorithm   ! -------------------------------------------------------- !  type polygon    !type for polygons    ! when you define a polygon, the first and the last vertices have to be the same    integer :: n    double precision, dimension(:,:), allocatable :: vertex  end type polygon   contains    ! -------------------------------------------------------- !  subroutine sutherlandHodgman( ref, clip, outputPolygon )    ! Sutherland Hodgman algorithm for 2d polygons     ! -- parameters of the subroutine --    type(polygon) :: ref, clip, outputPolygon     ! -- variables used is the subroutine    type(polygon) :: workPolygon               ! polygon clipped step by step     double precision, dimension(2) :: y1,y2    ! vertices of edge to clip workPolygon    integer :: i       ! allocate workPolygon with the maximal possible size    !   the sum of the size of polygon ref and clip    allocate(workPolygon%vertex( ref%n+clip%n , 2 ))     !  initialise the work polygon with clip    workPolygon%n = clip%n    workPolygon%vertex(1:workPolygon%n,:) = clip%vertex(1:workPolygon%n,:)     do i=1,ref%n-1 ! for each edge i of the polygon ref      y1(:) = ref%vertex(i,:)   !  vertex 1 of edge i      y2(:) = ref%vertex(i+1,:) !  vertex 2 of edge i       ! clip the work polygon by edge i      call edgeClipping( workPolygon, y1, y2, outputPolygon)      ! workPolygon <= outputPolygon      workPolygon%n = outputPolygon%n      workPolygon%vertex(1:workPolygon%n,:) = outputPolygon%vertex(1:workPolygon%n,:)     end do     deallocate(workPolygon%vertex)  end subroutine sutherlandHodgman   ! -------------------------------------------------------- !  subroutine edgeClipping( poly, y1, y2, outputPoly )    ! make the clipping  of the polygon by the line (x1x2)     type(polygon) :: poly, outputPoly    double precision, dimension(2) :: y1, y2, x1, x2, intersecPoint    integer ::  i, c     c = 0 ! counter for the output polygon     do i=1,poly%n-1 ! for each edge i of poly      x1(:) = poly%vertex(i,:)   ! vertex 1 of edge i      x2(:) = poly%vertex(i+1,:) ! vertex 2 of edge i       if ( inside(x1, y1, y2) ) then ! if vertex 1 in inside clipping region        if ( inside(x2, y1, y2) ) then ! if vertex 2 in inside clipping region          ! add the vertex 2 to the output polygon          c = c+1          outputPoly%vertex(c,:) = x2(:)         else ! vertex i+1 is outside          intersecPoint = intersection(x1, x2, y1,y2)          c = c+1          outputPoly%vertex(c,:) = intersecPoint(:)        end if      else ! vertex i is outside        if ( inside(x2, y1, y2) ) then          intersecPoint = intersection(x1, x2, y1,y2)          c = c+1          outputPoly%vertex(c,:) = intersecPoint(:)           c = c+1          outputPoly%vertex(c,:) = x2(:)        end if      end if    end do     if (c .gt. 0) then      ! if the last vertice is not equal to the first one      if ( (outputPoly%vertex(1,1) .ne. outputPoly%vertex(c,1)) .or. &            (outputPoly%vertex(1,2) .ne. outputPoly%vertex(c,2)))  then        c=c+1        outputPoly%vertex(c,:) = outputPoly%vertex(1,:)      end if    end if    ! set the size of the outputPolygon    outputPoly%n = c  end subroutine edgeClipping   ! -------------------------------------------------------- !  function intersection( x1, x2, y1, y2)    ! computes the intersection between segment [x1x2]     ! and line the line (y1y2)      ! -- parameters of the function --    double precision, dimension(2) :: x1, x2, &  ! points of the segment                                      y1, y2     ! points of the line     double precision, dimension(2) :: intersection, vx, vy, x1y1     double precision :: a     vx(:) = x2(:) - x1(:)     vy(:) = y2(:) - y1(:)     ! if the vectors are colinear    if ( crossProduct(vx,vy) .eq. 0.d0) then      x1y1(:) = y1(:) - x1(:)      ! if the the segment [x1x2] is included in the line (y1y2)      if ( crossProduct(x1y1,vx) .eq. 0.d0) then        ! the intersection is the last point of the segment        intersection(:) = x2(:)      end if    else ! the vectors are not colinear      ! we want to find the inersection between [x1x2]      ! and (y1,y2).      ! mathematically, we want to find a in [0;1] such      ! that :      !     x1 + a vx = y1 + b vy              ! <=> a vx = x1y1 + b vy      ! <=> a vx^vy = x1y1^vy      , ^ is cross product      ! <=> a = x1y1^vy / vx^vy       x1y1(:) = y1(:) - x1(:)       ! we compute a      a = crossProduct(x1y1,vy)/crossProduct(vx,vy)      ! if a is not in [0;1]      if ( (a .gt. 1.d0) .or. (a .lt. 0)) then        ! no intersection      else        intersection(:) = x1(:) + a*vx(:)      end if    end if   end function intersection    ! -------------------------------------------------------- !  function inside( p, y1, y2)    ! function that tells is the point p is at left of the line (y1y2)     double precision, dimension(2) :: p, y1, y2, v1, v2    logical :: inside    v1(:) = y2(:) -  y1(:)    v2(:) = p(:)  -  y1(:)      if ( crossProduct(v1,v2) .ge. 0.d0) then      inside = .true.    else       inside = .false.    end if    contains   end function inside   ! -------------------------------------------------------- !  function dotProduct( v1, v2)    ! compute the dot product of vectors v1 and v2    double precision, dimension(2) :: v1    double precision, dimension(2) :: v2    double precision :: dotProduct    dotProduct = v1(1)*v2(1) + v1(2)*v2(2)  end function dotProduct   ! -------------------------------------------------------- !  function crossProduct( v1, v2)    ! compute the crossproduct of vectors v1 and v2    double precision, dimension(2) :: v1    double precision, dimension(2) :: v2    double precision :: crossProduct    crossProduct = v1(1)*v2(2) - v1(2)*v2(1)  end function crossProduct end module SutherlandHodgmanUtil program main   ! load the module for S-H algorithm  use SutherlandHodgmanUtil, only : polygon, &                                    sutherlandHodgman, &                                    edgeClipping   type(polygon) :: p1, p2, res  integer :: c, n   double precision, dimension(2) :: y1, y2   ! when you define a polygon, the first and the last vertices have to be the same   ! first polygon  p1%n = 10  allocate(p1%vertex(p1%n,2))  p1%vertex(1,1)=50.d0  p1%vertex(1,2)=150.d0   p1%vertex(2,1)=200.d0  p1%vertex(2,2)=50.d0   p1%vertex(3,1)= 350.d0  p1%vertex(3,2)= 150.d0   p1%vertex(4,1)= 350.d0  p1%vertex(4,2)= 300.d0   p1%vertex(5,1)= 250.d0  p1%vertex(5,2)= 300.d0   p1%vertex(6,1)= 200.d0  p1%vertex(6,2)= 250.d0   p1%vertex(7,1)= 150.d0  p1%vertex(7,2)= 350.d0   p1%vertex(8,1)= 100.d0  p1%vertex(8,2)= 250.d0   p1%vertex(9,1)= 100.d0  p1%vertex(9,2)= 200.d0   p1%vertex(10,1)=  50.d0  p1%vertex(10,2)= 150.d0   y1 = (/ 100.d0, 300.d0 /)  y2 = (/ 300.d0, 300.d0 /)   ! second polygon  p2%n = 5  allocate(p2%vertex(p2%n,2))   p2%vertex(1,1)= 100.d0  p2%vertex(1,2)= 100.d0   p2%vertex(2,1)= 300.d0  p2%vertex(2,2)= 100.d0   p2%vertex(3,1)= 300.d0  p2%vertex(3,2)= 300.d0   p2%vertex(4,1)= 100.d0  p2%vertex(4,2)= 300.d0   p2%vertex(5,1)= 100.d0  p2%vertex(5,2)= 100.d0   allocate(res%vertex(p1%n+p2%n,2))  call sutherlandHodgman( p2, p1, res)  write(*,*) "Suterland-Hodgman"  do c=1, res%n    write(*,*) res%vertex(c,1), res%vertex(c,2)  end do  deallocate(res%vertex) end program main  `

Output:

```  Suterland-Hodgman
300.00000000000000        300.00000000000000
250.00000000000000        300.00000000000000
200.00000000000000        250.00000000000000
175.00000000000000        300.00000000000000
125.00000000000000        300.00000000000000
100.00000000000000        250.00000000000000
100.00000000000000        200.00000000000000
100.00000000000000        200.00000000000000
100.00000000000000        116.66666666666667
125.00000000000000        100.00000000000000
275.00000000000000        100.00000000000000
300.00000000000000        116.66666666666666
300.00000000000000        300.00000000000000
```

## Go

No extra credit today.

`package main import "fmt" type point struct {    x, y float32} var subjectPolygon = []point{{50, 150}, {200, 50}, {350, 150}, {350, 300},    {250, 300}, {200, 250}, {150, 350}, {100, 250}, {100, 200}} var clipPolygon = []point{{100, 100}, {300, 100}, {300, 300}, {100, 300}} func main() {    var cp1, cp2, s, e point    inside := func(p point) bool {        return (cp2.x-cp1.x)*(p.y-cp1.y) > (cp2.y-cp1.y)*(p.x-cp1.x)    }    intersection := func() (p point) {        dcx, dcy := cp1.x-cp2.x, cp1.y-cp2.y        dpx, dpy := s.x-e.x, s.y-e.y        n1 := cp1.x*cp2.y - cp1.y*cp2.x        n2 := s.x*e.y - s.y*e.x        n3 := 1 / (dcx*dpy - dcy*dpx)        p.x = (n1*dpx - n2*dcx) * n3        p.y = (n1*dpy - n2*dcy) * n3        return    }    outputList := subjectPolygon    cp1 = clipPolygon[len(clipPolygon)-1]    for _, cp2 = range clipPolygon { // WP clipEdge is cp1,cp2 here        inputList := outputList        outputList = nil        s = inputList[len(inputList)-1]        for _, e = range inputList {            if inside(e) {                if !inside(s) {                    outputList = append(outputList, intersection())                }                outputList = append(outputList, e)            } else if inside(s) {                outputList = append(outputList, intersection())            }            s = e        }        cp1 = cp2    }    fmt.Println(outputList)}`
Output:
```[{100 116.66667} {125 100} {275 100} {300 116.66667} {300 300} {250 300} {200 250} {175 300} {125 300} {100 250}]
```

(You can try it online)

`module SuthHodgClip (clipTo) where import Data.List type   Pt a = (a, a)type   Ln a = (Pt a, Pt a)type Poly a = [Pt a] -- Return a polygon from a list of points.polyFrom ps = last ps : ps -- Return a list of lines from a list of points.linesFrom pps@(_:ps) = zip pps ps -- Return true if the point (x,y) is on or to the left of the oriented line-- defined by (px,py) and (qx,qy).(.|) :: (Num a, Ord a) => Pt a -> Ln a -> Bool(x,y) .| ((px,py),(qx,qy)) = (qx-px)*(y-py) >= (qy-py)*(x-px) -- Return the intersection of two lines.(><) :: Fractional a => Ln a -> Ln a -> Pt a((x1,y1),(x2,y2)) >< ((x3,y3),(x4,y4)) =    let (r,s) = (x1*y2-y1*x2, x3*y4-y3*x4)        (t,u,v,w) = (x1-x2, y3-y4, y1-y2, x3-x4)        d = t*u-v*w     in ((r*w-t*s)/d, (r*u-v*s)/d) -- Intersect the line segment (p0,p1) with the clipping line's left halfspace,-- returning the point closest to p1.  In the special case where p0 lies outside-- the halfspace and p1 lies inside we return both the intersection point and-- p1.  This ensures we will have the necessary segment along the clipping line.(-|) :: (Fractional a, Ord a) => Ln a -> Ln a -> [Pt a]ln@(p0, p1) -| clipLn =    case (p0 .| clipLn, p1 .| clipLn) of      (False, False) -> []      (False, True)  -> [isect, p1]      (True,  False) -> [isect]      (True,  True)  -> [p1]    where isect = ln >< clipLn -- Intersect the polygon with the clipping line's left halfspace.(<|) :: (Fractional a, Ord a) => Poly a -> Ln a -> Poly apoly <| clipLn = polyFrom \$ concatMap (-| clipLn) (linesFrom poly) -- Intersect a target polygon with a clipping polygon.  The latter is assumed to-- be convex.clipTo :: (Fractional a, Ord a) => [Pt a] -> [Pt a] -> [Pt a]targPts `clipTo` clipPts =     let targPoly = polyFrom targPts        clipLines = linesFrom (polyFrom clipPts)    in foldl' (<|) targPoly clipLines`

Print the resulting list of points and display the polygons in a window.

`import Graphics.HGLimport SuthHodgClip targPts = [( 50,150), (200, 50), (350,150), (350,300), (250,300),            (200,250), (150,350), (100,250), (100,200)] :: [(Float,Float)]clipPts = [(100,100), (300,100), (300,300), (100,300)] :: [(Float,Float)] toInts = map (\(a,b) -> (round a, round b))complete xs = last xs : xs drawSolid w c = drawInWindow w . withRGB c . polygondrawLines w p = drawInWindow w . withPen p . polyline . toInts . complete blue  = RGB 0x99 0x99 0xffgreen = RGB 0x99 0xff 0x99pink  = RGB 0xff 0x99 0x99white = RGB 0xff 0xff 0xff main = do  let resPts = targPts `clipTo` clipPts      sz = 400      win = [(0,0), (sz,0), (sz,sz), (0,sz)]  runWindow "Sutherland-Hodgman Polygon Clipping" (sz,sz) \$ \w -> do         print \$ toInts resPts         penB <- createPen Solid 3 blue         penP <- createPen Solid 5 pink         drawSolid w white win         drawLines w penB targPts         drawLines w penP clipPts         drawSolid w green \$ toInts resPts         getKey w`
Output:
```[(100,200),(100,200),(100,117),(125,100),(275,100),(300,117),(300,300),(250,300),(200,250),(175,300),(125,300),(100,250),(100,200)]
```

## J

Solution:

`NB. assumes counterclockwise orientation.NB. determine whether point y is inside edge x.isinside=:0< [:-/ .* {.@[ -~"1 {:@[,:] NB. (p0,:p1) intersection (p2,:p3)intersection=:|:@[ (+/ .* (,-.)) [:{. ,.&(-~/) %.~ -&{: SutherlandHodgman=:4 :0 NB. clip S-H subject  clip=.2 ]\ (,{.) x  subject=.y  for_edge. clip do.    S=.{:input=.subject    subject=.0 2\$0    for_E. input do.      if. edge isinside E do.        if. -.edge isinside S do.          subject=.subject,edge intersection S,:E end.        subject=.subject,E      elseif. edge isinside S do.        subject=.subject,edge intersection S,:E end.      S=.E    end.  end.  subject)`
Example use:
`   subject=: 50 150,200 50,350 150,350 300,250 300,200 250,150 350,100 250,:100 200   clip=: 100 100,300 100,300 300,:100 300   clip SutherlandHodgman subject100 116.667125     100275     100300 116.667300     300250     300200     250175     300125     300100     250`

## Java

Works with: Java version 7
`import java.awt.*;import java.awt.geom.Line2D;import java.util.*;import java.util.List;import javax.swing.*; public class SutherlandHodgman extends JFrame {     SutherlandHodgmanPanel panel;     public static void main(String[] args) {        JFrame f = new SutherlandHodgman();        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);        f.setVisible(true);    }     public SutherlandHodgman() {        Container content = getContentPane();        content.setLayout(new BorderLayout());        panel = new SutherlandHodgmanPanel();        content.add(panel, BorderLayout.CENTER);        setTitle("SutherlandHodgman");        pack();        setLocationRelativeTo(null);    }} class SutherlandHodgmanPanel extends JPanel {    List<double[]> subject, clipper, result;     public SutherlandHodgmanPanel() {        setPreferredSize(new Dimension(600, 500));         // these subject and clip points are assumed to be valid        double[][] subjPoints = {{50, 150}, {200, 50}, {350, 150}, {350, 300},        {250, 300}, {200, 250}, {150, 350}, {100, 250}, {100, 200}};         double[][] clipPoints = {{100, 100}, {300, 100}, {300, 300}, {100, 300}};         subject = new ArrayList<>(Arrays.asList(subjPoints));        result  = new ArrayList<>(subject);        clipper = new ArrayList<>(Arrays.asList(clipPoints));         clipPolygon();    }     private void clipPolygon() {        int len = clipper.size();        for (int i = 0; i < len; i++) {             int len2 = result.size();            List<double[]> input = result;            result = new ArrayList<>(len2);             double[] A = clipper.get((i + len - 1) % len);            double[] B = clipper.get(i);             for (int j = 0; j < len2; j++) {                 double[] P = input.get((j + len2 - 1) % len2);                double[] Q = input.get(j);                 if (isInside(A, B, Q)) {                    if (!isInside(A, B, P))                        result.add(intersection(A, B, P, Q));                    result.add(Q);                } else if (isInside(A, B, P))                    result.add(intersection(A, B, P, Q));            }        }    }     private boolean isInside(double[] a, double[] b, double[] c) {        return (a[0] - c[0]) * (b[1] - c[1]) > (a[1] - c[1]) * (b[0] - c[0]);    }     private double[] intersection(double[] a, double[] b, double[] p, double[] q) {        double A1 = b[1] - a[1];        double B1 = a[0] - b[0];        double C1 = A1 * a[0] + B1 * a[1];         double A2 = q[1] - p[1];        double B2 = p[0] - q[0];        double C2 = A2 * p[0] + B2 * p[1];         double det = A1 * B2 - A2 * B1;        double x = (B2 * C1 - B1 * C2) / det;        double y = (A1 * C2 - A2 * C1) / det;         return new double[]{x, y};    }     @Override    public void paintComponent(Graphics g) {        super.paintComponent(g);        Graphics2D g2 = (Graphics2D) g;        g2.translate(80, 60);        g2.setStroke(new BasicStroke(3));        g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,                RenderingHints.VALUE_ANTIALIAS_ON);         drawPolygon(g2, subject, Color.blue);        drawPolygon(g2, clipper, Color.red);        drawPolygon(g2, result, Color.green);    }     private void drawPolygon(Graphics2D g2, List<double[]> points, Color color) {        g2.setColor(color);        int len = points.size();        Line2D line = new Line2D.Double();        for (int i = 0; i < len; i++) {            double[] p1 = points.get(i);            double[] p2 = points.get((i + 1) % len);            line.setLine(p1[0], p1[1], p2[0], p2[1]);            g2.draw(line);        }    }}`

## JavaScript

Solution:

` <html>    <head>	<script>        function clip (subjectPolygon, clipPolygon) {             var cp1, cp2, s, e;            var inside = function (p) {                return (cp2[0]-cp1[0])*(p[1]-cp1[1]) > (cp2[1]-cp1[1])*(p[0]-cp1[0]);            };            var intersection = function () {                var dc = [ cp1[0] - cp2[0], cp1[1] - cp2[1] ],                    dp = [ s[0] - e[0], s[1] - e[1] ],                    n1 = cp1[0] * cp2[1] - cp1[1] * cp2[0],                    n2 = s[0] * e[1] - s[1] * e[0],                     n3 = 1.0 / (dc[0] * dp[1] - dc[1] * dp[0]);                return [(n1*dp[0] - n2*dc[0]) * n3, (n1*dp[1] - n2*dc[1]) * n3];            };            var outputList = subjectPolygon;            cp1 = clipPolygon[clipPolygon.length-1];            for (j in clipPolygon) {                var cp2 = clipPolygon[j];                var inputList = outputList;                outputList = [];                s = inputList[inputList.length - 1]; //last on the input list                for (i in inputList) {                    var e = inputList[i];                    if (inside(e)) {                        if (!inside(s)) {                            outputList.push(intersection());                        }                        outputList.push(e);                    }                    else if (inside(s)) {                        outputList.push(intersection());                    }                    s = e;                }                cp1 = cp2;            }            return outputList        }         function drawPolygon(context, polygon, strokeStyle, fillStyle) {            context.strokeStyle = strokeStyle;            context.fillStyle = fillStyle;            context.beginPath();            context.moveTo(polygon[0][0],polygon[0][1]); //first vertex            for (var i = 1; i < polygon.length ; i++)                context.lineTo(polygon[i][0],polygon[i][1]);            context.lineTo(polygon[0][0],polygon[0][1]); //back to start            context.fill();            context.stroke();            context.closePath();        }         window.onload = function () {	        var context = document.getElementById('canvas').getContext('2d');	        var subjectPolygon = [[50, 150], [200, 50], [350, 150], [350, 300], [250, 300], [200, 250], [150, 350], [100, 250], [100, 200]],	            clipPolygon = [[100, 100], [300, 100], [300, 300], [100, 300]];	        var clippedPolygon = clip(subjectPolygon, clipPolygon);	        drawPolygon(context, clipPolygon, '#888','#88f');	        drawPolygon(context, subjectPolygon, '#888','#8f8');	        drawPolygon(context, clippedPolygon, '#000','#0ff');    	}        </script>    <body>    	<canvas id='canvas' width='400' height='400'></canvas>    </body></html> `

You can see it running `here`

## Lua

No extra credit.

Translation of: Go
`subjectPolygon = {  {50, 150}, {200, 50}, {350, 150}, {350, 300},  {250, 300}, {200, 250}, {150, 350}, {100, 250}, {100, 200}} clipPolygon = {{100, 100}, {300, 100}, {300, 300}, {100, 300}} function inside(p, cp1, cp2)  return (cp2.x-cp1.x)*(p.y-cp1.y) > (cp2.y-cp1.y)*(p.x-cp1.x)end function intersection(cp1, cp2, s, e)  local dcx, dcy = cp1.x-cp2.x, cp1.y-cp2.y  local dpx, dpy = s.x-e.x, s.y-e.y  local n1 = cp1.x*cp2.y - cp1.y*cp2.x  local n2 = s.x*e.y - s.y*e.x  local n3 = 1 / (dcx*dpy - dcy*dpx)  local x = (n1*dpx - n2*dcx) * n3  local y = (n1*dpy - n2*dcy) * n3  return {x=x, y=y}end function clip(subjectPolygon, clipPolygon)  local outputList = subjectPolygon  local cp1 = clipPolygon[#clipPolygon]  for _, cp2 in ipairs(clipPolygon) do  -- WP clipEdge is cp1,cp2 here    local inputList = outputList    outputList = {}    local s = inputList[#inputList]    for _, e in ipairs(inputList) do      if inside(e, cp1, cp2) then        if not inside(s, cp1, cp2) then          outputList[#outputList+1] = intersection(cp1, cp2, s, e)        end        outputList[#outputList+1] = e      elseif inside(s, cp1, cp2) then        outputList[#outputList+1] = intersection(cp1, cp2, s, e)      end      s = e    end    cp1 = cp2  end  return outputListend function main()  local function mkpoints(t)    for i, p in ipairs(t) do      p.x, p.y = p[1], p[2]    end  end  mkpoints(subjectPolygon)  mkpoints(clipPolygon)   local outputList = clip(subjectPolygon, clipPolygon)   for _, p in ipairs(outputList) do    print(('{%f, %f},'):format(p.x, p.y))  endend main()`
Output:
`{100.000000, 116.666667},{125.000000, 100.000000},{275.000000, 100.000000},{300.000000, 116.666667},{300.000000, 300.000000},{250.000000, 300.000000},{200.000000, 250.000000},{175.000000, 300.000000},{125.000000, 300.000000},{100.000000, 250.000000},`

(You can also see it live)

## MATLAB / Octave

`%The inputs are a table of x-y pairs for the verticies of the subject%polygon and boundary polygon. (x values in column 1 and y values in column%2) The output is a table of x-y pairs for the clipped version of the %subject polygon. function clippedPolygon = sutherlandHodgman(subjectPolygon,clipPolygon) %% Helper Functions     %computerIntersection() assumes the two lines intersect    function intersection = computeIntersection(line1,line2)         %this is an implementation of        %http://en.wikipedia.org/wiki/Line-line_intersection         intersection = zeros(1,2);         detL1 = det(line1);        detL2 = det(line2);         detL1x = det([line1(:,1),[1;1]]);        detL1y = det([line1(:,2),[1;1]]);         detL2x = det([line2(:,1),[1;1]]);        detL2y = det([line2(:,2),[1;1]]);         denominator = det([detL1x detL1y;detL2x detL2y]);         intersection(1) = det([detL1 detL1x;detL2 detL2x]) / denominator;        intersection(2) = det([detL1 detL1y;detL2 detL2y]) / denominator;     end %computeIntersection     %inside() assumes the boundary is oriented counter-clockwise    function in = inside(point,boundary)         pointPositionVector = [diff([point;boundary(1,:)]) 0];        boundaryVector = [diff(boundary) 0];        crossVector = cross(pointPositionVector,boundaryVector);         if ( crossVector(3) <= 0 )            in = true;        else            in = false;        end     end %inside %% Sutherland-Hodgman Algorithm     clippedPolygon = subjectPolygon;    numVerticies = size(clipPolygon,1);    clipVertexPrevious = clipPolygon(end,:);     for clipVertex = (1:numVerticies)         clipBoundary = [clipPolygon(clipVertex,:) ; clipVertexPrevious];         inputList = clippedPolygon;         clippedPolygon = [];        if ~isempty(inputList),            previousVertex = inputList(end,:);        end         for subjectVertex = (1:size(inputList,1))             if ( inside(inputList(subjectVertex,:),clipBoundary) )                 if( not(inside(previousVertex,clipBoundary)) )                      subjectLineSegment = [previousVertex;inputList(subjectVertex,:)];                    clippedPolygon(end+1,1:2) = computeIntersection(clipBoundary,subjectLineSegment);                end                 clippedPolygon(end+1,1:2) = inputList(subjectVertex,:);             elseif( inside(previousVertex,clipBoundary) )                    subjectLineSegment = [previousVertex;inputList(subjectVertex,:)];                    clippedPolygon(end+1,1:2) = computeIntersection(clipBoundary,subjectLineSegment);                                        end             previousVertex = inputList(subjectVertex,:);            clipVertexPrevious = clipPolygon(clipVertex,:);         end %for subject verticies                    end %for boundary verticiesend %sutherlandHodgman`
Output:
`>> subject = [[50;200;350;350;250;200;150;100;100],[150;50;150;300;300;250;350;250;200]];>> clipPolygon = [[100;300;300;100],[100;100;300;300]];>> clippedSubject = sutherlandHodgman(subject,clipPolygon);>> plot([subject(:,1);subject(1,1)],[subject(:,2);subject(1,2)],[0,0,1])>> hold on>> plot([clipPolygon(:,1);clipPolygon(1,1)],[clipPolygon(:,2);clipPolygon(1,2)],'r')>> patch(clippedSubject(:,1),clippedSubject(:,2),0);>> axis square`

## OCaml

`let is_inside (x,y) ((ax,ay), (bx,by)) =  (bx -. ax) *. (y -. ay) > (by -. ay) *. (x -. ax) let intersection (sx,sy) (ex,ey) ((ax,ay), (bx,by)) =  let dc_x, dc_y = (ax -. bx, ay -. by) in  let dp_x, dp_y = (sx -. ex, sy -. ey) in  let n1 = ax *. by -. ay *. bx in  let n2 = sx *. ey -. sy *. ex in  let n3 = 1.0 /. (dc_x *. dp_y -. dc_y *. dp_x) in  ((n1 *. dp_x -. n2 *. dc_x) *. n3,   (n1 *. dp_y -. n2 *. dc_y) *. n3) let last lst = List.hd (List.rev lst) let polygon_iter_edges poly f init =  if poly = [] then init else    let p0 = List.hd poly in    let rec aux acc = function      | p1 :: p2 :: tl -> aux (f (p1, p2) acc) (p2 :: tl)      | p :: [] -> f (p, p0) acc      | [] -> acc    in    aux init poly let poly_clip subject_polygon clip_polygon =  polygon_iter_edges clip_polygon (fun clip_edge input_list ->    fst (      List.fold_left (fun (out, s) e ->         match (is_inside e clip_edge), (is_inside s clip_edge) with        | true, false -> (e :: (intersection s e clip_edge) :: out), e        | true, true -> (e :: out), e        | false, true -> ((intersection s e clip_edge) :: out), e        | false, false -> (out, e)       ) ([], last input_list) input_list)   ) subject_polygon let () =  let subject_polygon =    [ ( 50.0, 150.0); (200.0,  50.0); (350.0, 150.0);      (350.0, 300.0); (250.0, 300.0); (200.0, 250.0);      (150.0, 350.0); (100.0, 250.0); (100.0, 200.0); ] in   let clip_polygon =    [ (100.0, 100.0); (300.0, 100.0); (300.0, 300.0); (100.0, 300.0) ] in   List.iter (fun (x,y) ->      Printf.printf " (%g, %g)\n" x y;    ) (poly_clip subject_polygon clip_polygon)`
Output:
``` (100, 116.667)
(125, 100)
(275, 100)
(300, 116.667)
(300, 300)
(250, 300)
(200, 250)
(175, 300)
(125, 300)
(100, 250)```

We can display the result in a window using the `Graphics` module:

`let subject_polygon =  [ ( 50.0, 150.0); (200.0,  50.0); (350.0, 150.0);    (350.0, 300.0); (250.0, 300.0); (200.0, 250.0);    (150.0, 350.0); (100.0, 250.0); (100.0, 200.0); ] let clip_polygon =  [ (100.0, 100.0); (300.0, 100.0); (300.0, 300.0); (100.0, 300.0) ] let () =  Graphics.open_graph " 400x400";  let to_grid poly =    let round x = int_of_float (floor (x +. 0.5)) in    Array.map      (fun (x, y) -> (round x, round y))      (Array.of_list poly)  in  let draw_poly fill stroke poly =    let p = to_grid poly in    Graphics.set_color fill;    Graphics.fill_poly p;    Graphics.set_color stroke;    Graphics.draw_poly p;  in  draw_poly Graphics.red Graphics.blue subject_polygon;  draw_poly Graphics.cyan Graphics.blue clip_polygon;  draw_poly Graphics.magenta Graphics.blue (poly_clip subject_polygon clip_polygon);  let _ = Graphics.wait_next_event [Graphics.Button_down; Graphics.Key_pressed] in  Graphics.close_graph ()`

## PHP

` <?phpfunction clip (\$subjectPolygon, \$clipPolygon) {     function inside (\$p, \$cp1, \$cp2) {        return (\$cp2[0]-\$cp1[0])*(\$p[1]-\$cp1[1]) > (\$cp2[1]-\$cp1[1])*(\$p[0]-\$cp1[0]);    }     function intersection (\$cp1, \$cp2, \$e, \$s) {        \$dc = [ \$cp1[0] - \$cp2[0], \$cp1[1] - \$cp2[1] ];        \$dp = [ \$s[0] - \$e[0], \$s[1] - \$e[1] ];        \$n1 = \$cp1[0] * \$cp2[1] - \$cp1[1] * \$cp2[0];        \$n2 = \$s[0] * \$e[1] - \$s[1] * \$e[0];        \$n3 = 1.0 / (\$dc[0] * \$dp[1] - \$dc[1] * \$dp[0]);         return [(\$n1*\$dp[0] - \$n2*\$dc[0]) * \$n3, (\$n1*\$dp[1] - \$n2*\$dc[1]) * \$n3];    }     \$outputList = \$subjectPolygon;    \$cp1 = end(\$clipPolygon);    foreach (\$clipPolygon as \$cp2) {        \$inputList = \$outputList;        \$outputList = [];        \$s = end(\$inputList);        foreach (\$inputList as \$e) {            if (inside(\$e, \$cp1, \$cp2)) {                if (!inside(\$s, \$cp1, \$cp2)) {                    \$outputList[] = intersection(\$cp1, \$cp2, \$e, \$s);                }                \$outputList[] = \$e;            }            else if (inside(\$s, \$cp1, \$cp2)) {                \$outputList[] = intersection(\$cp1, \$cp2, \$e, \$s);            }            \$s = \$e;        }        \$cp1 = \$cp2;    }    return \$outputList;} \$subjectPolygon = [[50, 150], [200, 50], [350, 150], [350, 300], [250, 300], [200, 250], [150, 350], [100, 250], [100, 200]];\$clipPolygon = [[100, 100], [300, 100], [300, 300], [100, 300]];\$clippedPolygon = clip(\$subjectPolygon, \$clipPolygon); echo json_encode(\$clippedPolygon);echo "\n";?> `

## PureBasic

Translation of: Go
`Structure point_f  x.f  y.fEndStructure Procedure isInside(*p.point_f, *cp1.point_f, *cp2.point_f)    If (*cp2\x - *cp1\x) * (*p\y - *cp1\y) > (*cp2\y - *cp1\y) * (*p\x - *cp1\x)    ProcedureReturn 1  EndIf EndProcedure Procedure intersection(*cp1.point_f, *cp2.point_f, *s.point_f, *e.point_f, *newPoint.point_f)  Protected.point_f dc, dp  Protected.f n1, n2, n3  dc\x = *cp1\x - *cp2\x: dc\y = *cp1\y - *cp2\y  dp\x = *s\x - *e\x: dp\y = *s\y - *e\y  n1 = *cp1\x * *cp2\y - *cp1\y * *cp2\x  n2 = *s\x * *e\y - *s\y * *e\x  n3 = 1 / (dc\x * dp\y - dc\y * dp\x)  *newPoint\x = (n1 * dp\x - n2 * dc\x) * n3: *newPoint\y = (n1 * dp\y - n2 * dc\y) * n3EndProcedure Procedure clip(List vPolygon.point_f(), List vClippedBy.point_f(), List vClippedPolygon.point_f())  Protected.point_f cp1, cp2, s, e, newPoint  CopyList(vPolygon(), vClippedPolygon())  If LastElement(vClippedBy())    cp1 = vClippedBy()     NewList vPreClipped.point_f()    ForEach vClippedBy()      cp2 = vClippedBy()      CopyList(vClippedPolygon(), vPreClipped())      ClearList(vClippedPolygon())      If LastElement(vPreClipped())        s = vPreClipped()        ForEach vPreClipped()          e = vPreClipped()          If isInside(e, cp1, cp2)            If Not isInside(s, cp1, cp2)              intersection(cp1, cp2, s, e, newPoint)              AddElement(vClippedPolygon()): vClippedPolygon() = newPoint            EndIf             AddElement(vClippedPolygon()): vClippedPolygon() = e          ElseIf isInside(s, cp1, cp2)            intersection(cp1, cp2, s, e, newPoint)            AddElement(vClippedPolygon()): vClippedPolygon() = newPoint          EndIf           s = e        Next      EndIf       cp1 = cp2    Next   EndIf EndProcedure DataSection  Data.f 50,150, 200,50, 350,150, 350,300, 250,300, 200,250, 150,350, 100,250, 100,200 ;subjectPolygon's vertices (x,y)  Data.f 100,100, 300,100, 300,300, 100,300 ;clipPolygon's vertices (x,y)EndDataSection NewList subjectPolygon.point_f()For i = 1 To 9  AddElement(subjectPolygon())  Read.f subjectPolygon()\x  Read.f subjectPolygon()\yNext  NewList clipPolygon.point_f()For i = 1 To 4  AddElement(clipPolygon())  Read.f clipPolygon()\x  Read.f clipPolygon()\yNext  NewList newPolygon.point_f()clip(subjectPolygon(), clipPolygon(), newPolygon())If OpenConsole()  ForEach newPolygon()    PrintN("(" + StrF(newPolygon()\x, 2) + ", " + StrF(newPolygon()\y, 2) + ")")  Next   Print(#CRLF\$ + #CRLF\$ + "Press ENTER to exit"): Input()  CloseConsole()EndIf`
Output:
```(100.00, 116.67)
(125.00, 100.00)
(275.00, 100.00)
(300.00, 116.67)
(300.00, 300.00)
(250.00, 300.00)
(200.00, 250.00)
(175.00, 300.00)
(125.00, 300.00)
(100.00, 250.00)```

## Python

` def clip(subjectPolygon, clipPolygon):   def inside(p):      return(cp2[0]-cp1[0])*(p[1]-cp1[1]) > (cp2[1]-cp1[1])*(p[0]-cp1[0])    def computeIntersection():      dc = [ cp1[0] - cp2[0], cp1[1] - cp2[1] ]      dp = [ s[0] - e[0], s[1] - e[1] ]      n1 = cp1[0] * cp2[1] - cp1[1] * cp2[0]      n2 = s[0] * e[1] - s[1] * e[0]       n3 = 1.0 / (dc[0] * dp[1] - dc[1] * dp[0])      return [(n1*dp[0] - n2*dc[0]) * n3, (n1*dp[1] - n2*dc[1]) * n3]    outputList = subjectPolygon   cp1 = clipPolygon[-1]    for clipVertex in clipPolygon:      cp2 = clipVertex      inputList = outputList      outputList = []      s = inputList[-1]       for subjectVertex in inputList:         e = subjectVertex         if inside(e):            if not inside(s):               outputList.append(computeIntersection())            outputList.append(e)         elif inside(s):            outputList.append(computeIntersection())         s = e      cp1 = cp2   return(outputList) `

## Racket

Shameless rewrite of haskell version.

`#lang racket (module sutherland-hodgman racket  (provide clip-to)  (provide make-edges)  (provide (struct-out point))   (struct point (x y) #:transparent)  (struct edge (p1 p2) #:transparent)  (struct polygon (points edges) #:transparent)   (define (make-edges points)    (let ([points-shifted	   (match points	     [(list a b ...) (append b (list a))])])      (map edge points points-shifted)))   (define (is-point-left? pt ln)    (match-let ([(point x y) pt]                [(edge (point px py) (point qx qy)) ln])               (>= (* (- qx px) (- y py))                   (* (- qy py) (- x px)))))   ;; Return the intersection of two lines  (define (isect-lines l1 l2)    (match-let ([(edge (point x1 y1) (point x2 y2)) l1]                [(edge (point x3 y3) (point x4 y4)) l2])               (let* ([r (- (* x1 y2) (* y1 x2))] [s (- (* x3 y4) (* y3 x4))]                      [t (- x1 x2)] [u (- y3 y4)] [v (- y1 y2)] [w (- x3 x4)]                      [d (- (* t u) (* v w))])                 (point (/ (- (* r w) (* t s)) d)                        (/ (- (* r u) (* v s)) d)))))   ;; Intersect the line segment (p0,p1) with the clipping line's left halfspace,   ;; returning the point closest to p1.  In the special case where p0 lies outside    ;; the halfspace and p1 lies inside we return both the intersection point and p1.    ;; This ensures we will have the necessary segment along the clipping line.   (define (intersect segment clip-line)    (define (isect) (isect-lines segment clip-line))     (match-let ([(edge p0 p1) segment])               (match/values (values (is-point-left? p0 clip-line) (is-point-left? p1 clip-line))                             [(#f #f) '()]                             [(#f #t) (list (isect) p1)]                             [(#t #f) (list (isect))]                             [(#t #t) (list p1)])))   ;; Intersect the polygon with the clipping line's left halfspace  (define (isect-polygon poly-edges clip-line)    (for/fold ([p '()]) ([e  poly-edges])      (append p (intersect e clip-line))))   ;; Intersect a subject polygon with a clipping polygon.  The latter is assumed to be convex.  (define (clip-to sp-pts cp-edges)    (for/fold ([out-poly sp-pts]) ([clip-line cp-edges])      (isect-polygon (make-edges out-poly) clip-line)))) `

Testing code (Couldn't find a way to attach image with polygons)

`(require racket/gui)  (require 'sutherland-hodgman) (define (make-points pt-list)    (for/list ([p pt-list])      (make-object point% (point-x p) (point-y p)))) (define subject-poly-points     (list (point 50 150)  (point 200 50)  (point 350 150)           (point 350 300) (point 250 300) (point 200 250)           (point 150 350) (point 100 250) (point 100 200))) (define clip-poly-points    (list (point 100 100)          (point 300 100)          (point 300 300)          (point 100 300))) (define clip-poly-edges     (make-edges clip-poly-points)) (define (run)  (let* ([frame (new frame% [label "Sutherland-Hodgman racket demo"]		     [width 320]		     [height 320])]	 [canvas (new canvas% [parent frame])]	 [dc (send canvas get-dc)]         [clipped-poly (clip-to subject-poly-points clip-poly-edges)])     (send frame show #t)    (sleep/yield 1)     (send dc set-pen (make-pen                         #:color (send the-color-database find-color "Blue")                        #:width 3))    (send dc draw-polygon (make-points subject-poly-points))    (send dc set-pen (make-pen                         #:color (send the-color-database find-color "Red")                        #:width 4                        #:style 'long-dash))    (send dc draw-polygon (make-points clip-poly-points))    (send dc set-pen (make-pen                         #:color (send the-color-database find-color "Green")))    (send dc set-brush (make-brush                         #:color (send the-color-database find-color "Green")                        #:style 'solid))    (send dc draw-polygon (make-points clipped-poly))    clipped-poly)) (run)`

Output:

`(list (point 300 300) (point 250 300) (point 200 250) (point 175 300) (point 125 300) (point 100 250) (point 100 200) (point 100 200) (point 100 350/3) (point 125 100) (point 275 100) (point 300 350/3))`

## Ruby

Translation of: Go
`Point = Struct.new(:x,:y) do  def to_s; "(#{x}, #{y})" endend def sutherland_hodgman(subjectPolygon, clipPolygon)  # These inner functions reduce the argument passing to  # "inside" and "intersection".  cp1, cp2, s, e = nil  inside = proc do |p|    (cp2.x-cp1.x)*(p.y-cp1.y) > (cp2.y-cp1.y)*(p.x-cp1.x)  end  intersection = proc do    dcx, dcy = cp1.x-cp2.x, cp1.y-cp2.y    dpx, dpy = s.x-e.x, s.y-e.y    n1 = cp1.x*cp2.y - cp1.y*cp2.x    n2 = s.x*e.y - s.y*e.x    n3 = 1.0 / (dcx*dpy - dcy*dpx)    Point[(n1*dpx - n2*dcx) * n3, (n1*dpy - n2*dcy) * n3]  end   outputList = subjectPolygon  cp1 = clipPolygon.last  for cp2 in clipPolygon    inputList = outputList    outputList = []    s = inputList.last    for e in inputList      if inside[e]        outputList << intersection[] unless inside[s]        outputList << e      elsif inside[s]        outputList << intersection[]      end      s = e    end    cp1 = cp2  end  outputListend subjectPolygon = [[50, 150], [200, 50], [350, 150], [350, 300],                  [250, 300], [200, 250], [150, 350], [100, 250],                  [100, 200]].collect{|pnt| Point[*pnt]} clipPolygon = [[100, 100], [300, 100], [300, 300], [100, 300]].collect{|pnt| Point[*pnt]} puts sutherland_hodgman(subjectPolygon, clipPolygon)`
Output:
```(100.0, 116.66666666666667)
(125.00000000000001, 100.0)
(275.0, 100.0)
(300.0, 116.66666666666667)
(300.0, 299.99999999999994)
(250.0, 300.0)
(200, 250)
(175.0, 300.0)
(125.0, 300.0)
(100.0, 250.0)
```

## Scala

From Java snippet.

`import javax.swing.{ JFrame, JPanel } object SutherlandHodgman extends JFrame with App {    import java.awt.BorderLayout     setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE)    setVisible(true)    val content = getContentPane()    content.setLayout(new BorderLayout())    content.add(SutherlandHodgmanPanel, BorderLayout.CENTER)    setTitle("SutherlandHodgman")    pack()    setLocationRelativeTo(null)} object SutherlandHodgmanPanel extends JPanel {    import java.awt.{ Color, Graphics, Graphics2D }     setPreferredSize(new java.awt.Dimension(600, 500))     // subject and clip points are assumed to be valid    val subject = Seq((50D, 150D), (200D, 50D), (350D, 150D), (350D, 300D), (250D, 300D), (200D, 250D), (150D, 350D), (100D, 250D), (100D, 200D))    val clipper = Seq((100D, 100D), (300D, 100D), (300D, 300D), (100D, 300D))    var result = subject     val len = clipper.size    for (i <- 0 until len) {        val len2 = result.size        val input = result        result = Seq()         val A = clipper((i + len - 1) % len)        val B = clipper(i)         for (j <- 0 until len2) {            val P = input((j + len2 - 1) % len2)            val Q = input(j)             if (inside(A, B, Q)) {                if (!inside(A, B, P))                    result = result :+ intersection(A, B, P, Q)                result = result :+ Q            }            else if (inside(A, B, P))                result = result :+ intersection(A, B, P, Q)        }    }     override def paintComponent(g: Graphics) {        import java.awt.RenderingHints._         super.paintComponent(g)        val g2 = g.asInstanceOf[Graphics2D]        g2.translate(80, 60)        g2.setStroke(new java.awt.BasicStroke(3))        g2.setRenderingHint(KEY_ANTIALIASING, VALUE_ANTIALIAS_ON)        g2.draw_polygon(subject, Color.blue)        g2.draw_polygon(clipper, Color.red)        g2.draw_polygon(result, Color.green)    }     private def inside(a: (Double, Double), b: (Double, Double), c: (Double, Double)) =        (a._1 - c._1) * (b._2 - c._2) > (a._2 - c._2) * (b._1 - c._1)     private def intersection(a: (Double, Double), b: (Double, Double), p: (Double, Double), q: (Double, Double)) = {        val A1 = b._2 - a._2        val B1 = a._1 - b._1        val C1 = A1 * a._1 + B1 * a._2        val A2 = q._2 - p._2        val B2 = p._1 - q._1        val C2 = A2 * p._1 + B2 * p._2         val det = A1 * B2 - A2 * B1        ((B2 * C1 - B1 * C2) / det, (A1 * C2 - A2 * C1) / det)    }     private implicit final class Polygon_drawing(g: Graphics2D) {        def draw_polygon(points: Seq[(Double, Double)], color: Color) {            g.setColor(color)            val len = points.length            val line = new java.awt.geom.Line2D.Double()            for (i <- 0 until len) {                val p1 = points(i)                val p2 = points((i + 1) % len)                line.setLine(p1._1, p1._2, p2._1, p2._2)                g.draw(line)            }        }    }}`

## Sidef

Translation of: Ruby
`class Point(x, y) {    method to_s {        "(#{'%.2f' % x}, #{'%.2f' % y})"    }} func sutherland_hodgman(subjectPolygon, clipPolygon) {  var inside = { |cp1, cp2, p|    ((cp2.x-cp1.x)*(p.y-cp1.y)) > ((cp2.y-cp1.y)*(p.x-cp1.x))  }   var intersection = { |cp1, cp2, s, e|    var (dcx, dcy) = (cp1.x-cp2.x, cp1.y-cp2.y)    var (dpx, dpy) = (s.x-e.x, s.y-e.y)    var n1 = (cp1.x*cp2.y - cp1.y*cp2.x)    var n2 = (s.x*e.y - s.y*e.x)    var n3 = (1 / (dcx*dpy - dcy*dpx))    Point((n1*dpx - n2*dcx) * n3, (n1*dpy - n2*dcy) * n3)  }   var outputList = subjectPolygon  var cp1 = clipPolygon.last  for cp2 in clipPolygon {    var inputList = outputList    outputList = []    var s = inputList.last    for e in inputList {      if (inside(cp1, cp2, e)) {        outputList << intersection(cp1, cp2, s, e) if !inside(cp1, cp2, s)        outputList << e      }      elsif(inside(cp1, cp2, s)) {        outputList << intersection(cp1, cp2, s, e)      }      s = e    }    cp1 = cp2  }  outputList} var subjectPolygon = [    [50,  150], [200,  50], [350, 150], [350, 300],    [250, 300], [200, 250], [150, 350], [100, 250],    [100, 200]].map{|pnt| Point(pnt...) } var clipPolygon = [    [100, 100], [300, 100],    [300, 300], [100, 300]].map{|pnt| Point(pnt...) } sutherland_hodgman(subjectPolygon, clipPolygon).each { .say }`
Output:
```(100.00, 116.67)
(125.00, 100.00)
(275.00, 100.00)
(300.00, 116.67)
(300.00, 300.00)
(250.00, 300.00)
(200.00, 250.00)
(175.00, 300.00)
(125.00, 300.00)
(100.00, 250.00)
```

## Tcl

`# Find intersection of an arbitrary polygon with a convex one.package require Tcl 8.6 #	Does the path (x0,y0)->(x1,y1)->(x2,y2) turn clockwise#	or counterclockwise?proc cw {x0 y0 x1 y1 x2 y2} {    set dx1 [expr {\$x1 - \$x0}]; set dy1 [expr {\$y1 - \$y0}]    set dx2 [expr {\$x2 - \$x0}]; set dy2 [expr {\$y2 - \$y0}]    # (0,0,\$dx1*\$dy2 - \$dx2*\$dy1) is the crossproduct of    # (\$x1-\$x0,\$y1-\$y0,0) and (\$x2-\$x0,\$y2-\$y0,0).     # Its z-component is positive if the turn    # is clockwise, negative if the turn is counterclockwise.    set pr1 [expr {\$dx1 * \$dy2}]    set pr2 [expr {\$dx2 * \$dy1}]    if {\$pr1 > \$pr2} {	# Clockwise	return 1    } elseif {\$pr1 < \$pr2} {	# Counter-clockwise	return -1    } elseif {\$dx1*\$dx2 < 0 || \$dy1*\$dy2 < 0} {	# point 0 is the middle point	return 0    } elseif {(\$dx1*\$dx1 + \$dy1*\$dy1) < (\$dx2*\$dx2 + \$dy2+\$dy2)} {	# point 1 is the middle point	return 0    } else {	# point 2 lies on the segment joining points 0 and 1	return 1    }} #	Calculate the point of intersection of two lines#	containing the line segments (x1,y1)-(x2,y2) and (x3,y3)-(x4,y4)proc intersect {x1 y1 x2 y2 x3 y3 x4 y4} {    set d [expr {(\$y4 - \$y3) * (\$x2 - \$x1) - (\$x4 - \$x3) * (\$y2 - \$y1)}]    set na [expr {(\$x4 - \$x3) * (\$y1 - \$y3) - (\$y4 - \$y3) * (\$x1 - \$x3)}]    if {\$d == 0} {	return {}    }    set r [list \	    [expr {\$x1 + \$na * (\$x2 - \$x1) / \$d}] \	    [expr {\$y1 + \$na * (\$y2 - \$y1) / \$d}]]    return \$r} #	Coroutine that yields the elements of a list in pairsproc pairs {list} {    yield [info coroutine]    foreach {x y} \$list {	yield [list \$x \$y]    }    return {}} #	Coroutine to clip one segment of a polygon against a line.proc clipsegment {inside0 cx0 cy0 cx1 cy1 sx0 sy0 sx1 sy1} {    set inside1 [expr {[cw \$cx0 \$cy0 \$cx1 \$cy1 \$sx1 \$sy1] > 0}]    if {\$inside1} {	if {!\$inside0} {	    set int [intersect \$cx0 \$cy0 \$cx1 \$cy1 \		    \$sx0 \$sy0 \$sx1 \$sy1]	    if {[llength \$int] >= 0} {		yield \$int	    }	}	yield [list \$sx1 \$sy1]    } else {	if {\$inside0} {	    set int [intersect \$cx0 \$cy0 \$cx1 \$cy1 \		    \$sx0 \$sy0 \$sx1 \$sy1]	    if {[llength \$int] >= 0} {		yield \$int	    }	}    }    return \$inside1} #	Coroutine to perform one step of Sutherland-Hodgman polygon clippingproc clipstep {source cx0 cy0 cx1 cy1} {    yield [info coroutine]    set pt0 [{*}\$source]    if {[llength \$pt0] == 0} {	return    }    lassign \$pt0 sx0 sy0    set inside0 [expr {[cw \$cx0 \$cy0 \$cx1 \$cy1 \$sx0 \$sy0] > 0}]    set finished 0    while {!\$finished} {	set thispt [{*}\$source]	if {[llength \$thispt] == 0} {	    set thispt \$pt0	    set finished 1	}	lassign \$thispt sx1 sy1	set inside0 [clipsegment \$inside0 \		\$cx0 \$cy0 \$cx1 \$cy1 \$sx0 \$sy0 \$sx1 \$sy1]	set sx0 \$sx1	set sy0 \$sy1    }    return {}} #	Perform Sutherland-Hodgman polygon clippingproc clippoly {cpoly spoly} {    variable clipindx    set source [coroutine clipper[incr clipindx] pairs \$spoly]    set cx0 [lindex \$cpoly end-1]    set cy0 [lindex \$cpoly end]    foreach {cx1 cy1} \$cpoly {	set source [coroutine clipper[incr clipindx] \		clipstep \$source \$cx0 \$cy0 \$cx1 \$cy1]	set cx0 \$cx1; set cy0 \$cy1    }    set result {}    while {[llength [set pt [{*}\$source]]] > 0} {	lappend result {*}\$pt    }    return \$result}`

The specifics of the task:

Library: Tk
`package require Tk grid [canvas .c -width 400 -height 400 -background \#ffffff]proc demonstrate {cpoly spoly} {    set rpoly [clippoly \$cpoly \$spoly]    puts \$rpoly    .c create polygon \$cpoly -outline \#ff9999 -fill {} -width 5     .c create polygon \$spoly -outline \#9999ff -fill {} -width 3    .c create polygon \$rpoly -fill \#99ff99 -outline black -width 1} demonstrate {100 100 300 100 300 300 100 300} \    {50 150 200 50 350 150 350 300 250 300 200 250 150 350 100 250 100 200}`
Output:
```300 116 300 300 250 300 200 250 175 300 125 300 100 250 100 200 100 200 100 116 124 100 275 100
```

## zkl

Translation of: C
Translation of: Wikipedia

Uses the PPM class from http://rosettacode.org/wiki/Bitmap/Bresenham%27s_line_algorithm#zkl

`class P{	// point   fcn init(_x,_y){ var [const] x=_x.toFloat(), y=_y.toFloat() }   fcn __opSub(p) { self(x - p.x, y - p.y) }   fcn cross(p)   { x*p.y - y*p.x          }   fcn toString   { "(%7.2f,%7.2f)".fmt(x,y) }   var [const,proxy] ps=fcn{ T(x.toInt(),y.toInt()) };    // property}fcn shClipping(clip,polygon){   inputList,outputList,clipEdge:=List(), polygon.copy(), List(Void,clip[-1]);   foreach p in (clip){      clipEdge.del(0).append(p);      inputList.clear().extend(outputList);      outputList.clear();      S:=inputList[-1];      foreach E in (inputList){         if(leftOf(clipEdge,E)){	    if(not leftOf(clipEdge,S))	       outputList.append(intersection(S,E,clipEdge));	    outputList.append(E);	 }	 else if(leftOf(clipEdge,S))	         outputList.append(intersection(S,E,clipEdge));	 S=E;      }   }   outputList}fcn leftOf(line,p){ //-->True (p is left of line), direction of line matters   p1,p2:=line;		// line is (p1,p2)   (p2-p1).cross(p-p2)>0;}fcn intersection(p1,p2, line){	//-->Point of intersection or False   p3,p4:=line;   dx,dy,d:=p2-p1, p3-p4, p1-p3;   // x0 + a dx = y0 + b dy ->   // x0 X dx = y0 X dx + b dy X dx ->   // b = (x0 - y0) X dx / (dy X dx)   dyx:=dy.cross(dx);   if(not dyx) return(False);  // parallel lines, could just throw on next line   dyx=d.cross(dx)/dyx;   P(p3.x + dyx*dy.x, p3.y + dyx*dy.y);}fcn drawPolygon(ppm,listOfPoints,rgb){   foreach n in (listOfPoints.len()-1){      ppm.line(listOfPoints[n].ps.xplode(),listOfPoints[n+1].ps.xplode(),rgb);   }   ppm.line(listOfPoints[0].ps.xplode(),listOfPoints[-1].ps.xplode(),rgb);}`
`ppm:=PPM(400,400);clip:=T( P(100,100), P(300,100), P(300,300), P(100,300) );polygon:=T( P( 50,150),P(200, 50),P(350,150),	    P(350,300),P(250,300),P(200,250),	    P(150,350),P(100,250),P(100,200) );drawPolygon(ppm,polygon,0x0000ff);	// blue: polygonppm.flood(200,200,0x000030);drawPolygon(ppm,clip,0xff0000);		// red:  clip region clipped:=shClipping(clip,polygon);drawPolygon(ppm,clipped,0x00ff00);	// green: clipped polygonppm.flood(200,200,0x003000);		// which is the clipped region anywayclipped.apply('wrap(p){ ppm.cross(p.ps.xplode(),0x00ff00) }); // mark vertices ppm.writeJPGFile("sutherland_hodgman.zkl.jpg"); println("Clipped polygon has ",clipped.len()," points:");clipped.pump(Console.println);`
Output:

Until local image uploading is re-enabled, see this image.

```Clipped polygon has 10 points:
( 100.00, 116.67)
( 125.00, 100.00)
( 275.00, 100.00)
( 300.00, 116.67)
( 300.00, 300.00)
( 250.00, 300.00)
( 200.00, 250.00)
( 175.00, 300.00)
( 125.00, 300.00)
( 100.00, 250.00)
```