Xiaolin Wu's line algorithm
You are encouraged to solve this task according to the task description, using any language you may know.
Implement the Xiaolin Wu's line algorithm as described in Wikipedia. This algorithm draw antialiased lines. See Bresenham's line algorithm for aliased lines.
AutoHotkey
<lang AutoHotkey>#SingleInstance, Force
- NoEnv
SetBatchLines, -1
pToken := Gdip_Startup() global pBitmap := Gdip_CreateBitmap(500, 500) drawLine(100,50,400,400) Gdip_SaveBitmapToFile(pBitmap, A_ScriptDir "\linetest.png") Gdip_DisposeImage(pBitmap) Gdip_Shutdown(pToken) Run, % A_ScriptDir "\linetest.png" ExitApp
plot(x, y, c) {
A := DecToBase(255 * c, 16) Gdip_SetPixel(pBitmap, x, y, "0x" A "000000")
}
- integer part of x
ipart(x) {
return x // 1
}
rnd(x) {
return ipart(x + 0.5)
}
- fractional part of x
fpart(x) {
if (x < 0) return 1 - (x - floor(x)) return x - floor(x)
}
rfpart(x) {
return 1 - fpart(x)
}
drawLine(x0,y0,x1,y1) {
steep := abs(y1 - y0) > abs(x1 - x0) if (steep) { temp := x0, x0 := y0, y0 := temp temp := x1, x1 := y1, y1 := temp } if (x0 > x1 then) { temp := x0, x0 := x1, x1 := temp temp := y0, y0 := y1, y1 := temp } dx := x1 - x0 dy := y1 - y0 gradient := dy / dx ; handle first endpoint xend := rnd(x0) yend := y0 + gradient * (xend - x0) xgap := rfpart(x0 + 0.5) xpxl1 := xend ; this will be used in the main loop ypxl1 := ipart(yend) if (steep) { plot(ypxl1, xpxl1, rfpart(yend) * xgap) plot(ypxl1+1, xpxl1, fpart(yend) * xgap) } else { plot(xpxl1, ypxl1 , rfpart(yend) * xgap) plot(xpxl1, ypxl1+1, fpart(yend) * xgap) } intery := yend + gradient ; first y-intersection for the main loop ; handle second endpoint xend := rnd(x1) yend := y1 + gradient * (xend - x1) xgap := fpart(x1 + 0.5) xpxl2 := xend ;this will be used in the main loop ypxl2 := ipart(yend) if (steep) { plot(ypxl2 , xpxl2, rfpart(yend) * xgap) plot(ypxl2+1, xpxl2, fpart(yend) * xgap) } else { plot(xpxl2, ypxl2, rfpart(yend) * xgap) plot(xpxl2, ypxl2+1, fpart(yend) * xgap) } ; main loop while (x := xpxl1 + A_Index) < xpxl2 { if (steep) { plot(ipart(intery) , x, rfpart(intery)) plot(ipart(intery)+1, x, fpart(intery)) } else { plot(x, ipart (intery), rfpart(intery)) plot(x, ipart (intery)+1, fpart(intery)) } intery := intery + gradient }
}
DecToBase(n, Base) {
static U := A_IsUnicode ? "w" : "a" VarSetCapacity(S,65,0) DllCall("msvcrt\_i64to" U, "Int64",n, "Str",S, "Int",Base) return, S
}</lang>
BBC BASIC
<lang bbcbasic> PROCdrawAntiAliasedLine(100, 100, 600, 400, 0, 0, 0)
END DEF PROCdrawAntiAliasedLine(x1, y1, x2, y2, r%, g%, b%) LOCAL dx, dy, xend, yend, grad, yf, xgap, ix1%, iy1%, ix2%, iy2%, x% dx = x2 - x1 dy = y2 - y1 IF ABS(dx) < ABS(dy) THEN SWAP x1, y1 SWAP x2, y2 SWAP dx, dy ENDIF IF x2 < x1 THEN SWAP x1, x2 SWAP y1, y2 ENDIF grad = dy / dx xend = INT(x1 + 0.5) yend = y1 + grad * (xend - x1) xgap = xend + 0.5 - x1 ix1% = xend iy1% = INT(yend) PROCplot(ix1%, iy1%, r%, b%, g%, (INT(yend) + 1 - yend) * xgap) PROCplot(ix1%, iy1% + 1, r%, b%, g%, (yend - INT(yend)) * xgap) yf = yend + grad xend = INT(x2 + 0.5) yend = y2 + grad * (xend - x2) xgap = x2 + 0.5 - xend ix2% = xend iy2% = INT(yend) PROCplot(ix2%, iy2%, r%, b%, g%, (INT(yend) + 1 - yend) * xgap) PROCplot(ix2%, iy2% + 1, r%, b%, g%, (yend - INT(yend)) * xgap) FOR x% = ix1% + 1 TO ix2% - 1 PROCplot(x%, INT(yf), r%, b%, g%, INT(yf) + 1 - yf) PROCplot(x%, INT(yf) + 1, r%, b%, g%, yf - INT(yf)) yf += grad NEXT ENDPROC DEF PROCplot(X%, Y%, R%, G%, B%, a) LOCAL C% C% = TINT(X%*2,Y%*2) COLOUR 1, R%*a + (C% AND 255)*(1-a), \ \ G%*a + (C% >> 8 AND 255)*(1-a), \ \ B%*a + (C% >> 16 AND 255)*(1-a) GCOL 1 LINE X%*2, Y%*2, X%*2, Y%*2 ENDPROC</lang>
C
This implementation follows straightforwardly the pseudocode given on Wikipedia. (Further analysis of the code could give suggestions for improvements).
<lang c>void draw_line_antialias(
image img, unsigned int x0, unsigned int y0, unsigned int x1, unsigned int y1, color_component r, color_component g, color_component b );</lang>
<lang c>inline void _dla_changebrightness(rgb_color_p from, rgb_color_p to, float br) {
if ( br > 1.0 ) br = 1.0; /* linear... Maybe something more complex could give better look */ to->red = br * (float)from->red; to->green = br * (float)from->green; to->blue = br * (float)from->blue;
}
- define plot_(X,Y,D) do{ rgb_color f_; \
f_.red = r; f_.green = g; f_.blue = b; \ _dla_plot(img, (X), (Y), &f_, (D)) ; }while(0)
inline void _dla_plot(image img, int x, int y, rgb_color_p col, float br) {
rgb_color oc; _dla_changebrightness(col, &oc, br); put_pixel_clip(img, x, y, oc.red, oc.green, oc.blue);
}
- define ipart_(X) ((int)(X))
- define round_(X) ((int)(((double)(X))+0.5))
- define fpart_(X) (((double)(X))-(double)ipart_(X))
- define rfpart_(X) (1.0-fpart_(X))
- define swap_(a, b) do{ __typeof__(a) tmp; tmp = a; a = b; b = tmp; }while(0)
void draw_line_antialias(
image img, unsigned int x1, unsigned int y1, unsigned int x2, unsigned int y2, color_component r, color_component g, color_component b )
{
double dx = (double)x2 - (double)x1; double dy = (double)y2 - (double)y1; if ( fabs(dx) > fabs(dy) ) { if ( x2 < x1 ) { swap_(x1, x2); swap_(y1, y2); } double gradient = dy / dx; double xend = round_(x1); double yend = y1 + gradient*(xend - x1); double xgap = rfpart_(x1 + 0.5); int xpxl1 = xend; int ypxl1 = ipart_(yend); plot_(xpxl1, ypxl1, rfpart_(yend)*xgap); plot_(xpxl1, ypxl1+1, fpart_(yend)*xgap); double intery = yend + gradient;
xend = round_(x2); yend = y2 + gradient*(xend - x2); xgap = fpart_(x2+0.5); int xpxl2 = xend; int ypxl2 = ipart_(yend); plot_(xpxl2, ypxl2, rfpart_(yend) * xgap); plot_(xpxl2, ypxl2 + 1, fpart_(yend) * xgap);
int x; for(x=xpxl1+1; x <= (xpxl2-1); x++) { plot_(x, ipart_(intery), rfpart_(intery)); plot_(x, ipart_(intery) + 1, fpart_(intery)); intery += gradient; } } else { if ( y2 < y1 ) { swap_(x1, x2); swap_(y1, y2); } double gradient = dx / dy; double yend = round_(y1); double xend = x1 + gradient*(yend - y1); double ygap = rfpart_(y1 + 0.5); int ypxl1 = yend; int xpxl1 = ipart_(xend); plot_(xpxl1, ypxl1, rfpart_(xend)*ygap); plot_(xpxl1, ypxl1+1, fpart_(xend)*ygap); double interx = xend + gradient;
yend = round_(y2); xend = x2 + gradient*(yend - y2); ygap = fpart_(y2+0.5); int ypxl2 = yend; int xpxl2 = ipart_(xend); plot_(xpxl2, ypxl2, rfpart_(xend) * ygap); plot_(xpxl2, ypxl2 + 1, fpart_(xend) * ygap);
int y; for(y=ypxl1+1; y <= (ypxl2-1); y++) { plot_(ipart_(interx), y, rfpart_(interx)); plot_(ipart_(interx) + 1, y, fpart_(interx)); interx += gradient; } }
}
- undef swap_
- undef plot_
- undef ipart_
- undef fpart_
- undef round_
- undef rfpart_</lang>
C#
<lang c> public class Line
{ private double x0, y0, x1, y1; private Color foreColor; private byte lineStyleMask; private int thickness; private float globalm;
public Line(double x0, double y0, double x1, double y1, Color color, byte lineStyleMask, int thickness) { this.x0 = x0; this.y0 = y0; this.y1 = y1; this.x1 = x1;
this.foreColor = color;
this.lineStyleMask = lineStyleMask;
this.thickness = thickness;
}
private void plot(Bitmap bitmap, double x, double y, double c) { int alpha = (int)(c * 255); if (alpha > 255) alpha = 255; if (alpha < 0) alpha = 0; Color color = Color.FromArgb(alpha, foreColor); if (BitmapDrawHelper.checkIfInside((int)x, (int)y, bitmap)) { bitmap.SetPixel((int)x, (int)y, color); } }
int ipart(double x) { return (int)x;}
int round(double x) {return ipart(x+0.5);} double fpart(double x) { if(x<0) return (1-(x-Math.Floor(x))); return (x-Math.Floor(x)); } double rfpart(double x) { return 1-fpart(x); }
public void draw(Bitmap bitmap) { bool steep = Math.Abs(y1-y0)>Math.Abs(x1-x0); double temp; if(steep){ temp=x0; x0=y0; y0=temp; temp=x1;x1=y1;y1=temp; } if(x0>x1){ temp = x0;x0=x1;x1=temp; temp = y0;y0=y1;y1=temp; }
double dx = x1-x0; double dy = y1-y0; double gradient = dy/dx;
double xEnd = round(x0); double yEnd = y0+gradient*(xEnd-x0); double xGap = rfpart(x0+0.5); double xPixel1 = xEnd; double yPixel1 = ipart(yEnd);
if(steep){ plot(bitmap, yPixel1, xPixel1, rfpart(yEnd)*xGap); plot(bitmap, yPixel1+1, xPixel1, fpart(yEnd)*xGap); }else{ plot(bitmap, xPixel1,yPixel1, rfpart(yEnd)*xGap); plot(bitmap, xPixel1, yPixel1+1, fpart(yEnd)*xGap); } double intery = yEnd+gradient;
xEnd = round(x1); yEnd = y1+gradient*(xEnd-x1); xGap = fpart(x1+0.5); double xPixel2 = xEnd; double yPixel2 = ipart(yEnd); if(steep){ plot(bitmap, yPixel2, xPixel2, rfpart(yEnd)*xGap); plot(bitmap, yPixel2+1, xPixel2, fpart(yEnd)*xGap); }else{ plot(bitmap, xPixel2, yPixel2, rfpart(yEnd)*xGap); plot(bitmap, xPixel2, yPixel2+1, fpart(yEnd)*xGap); }
if(steep){ for(int x=(int)(xPixel1+1);x<=xPixel2-1;x++){ plot(bitmap, ipart(intery), x, rfpart(intery)); plot(bitmap, ipart(intery)+1, x, fpart(intery)); intery+=gradient; } }else{ for(int x=(int)(xPixel1+1);x<=xPixel2-1;x++){ plot(bitmap, x,ipart(intery), rfpart(intery)); plot(bitmap, x, ipart(intery)+1, fpart(intery)); intery+=gradient; } } } }
</lang>
D
This performs the mixing of the colors, both in grey scale and RGB. <lang d>import std.math, std.algorithm, grayscale_image;
/// Plots anti-aliased line by Xiaolin Wu's line algorithm. void aaLine(Color)(ref Image!Color img,
double x1, double y1, double x2, double y2, in Color color) pure nothrow @safe @nogc { // Straight translation of Wikipedia pseudocode.
// std.math.round is not pure. ** static double round(in double x) pure nothrow @safe @nogc { return floor(x + 0.5); }
static double fpart(in double x) pure nothrow @safe @nogc { return x - x.floor; }
static double rfpart(in double x) pure nothrow @safe @nogc { return 1 - fpart(x); }
auto dx = x2 - x1; auto dy = y2 - y1; immutable ax = dx.abs; immutable ay = dy.abs;
static Color mixColors(in Color c1, in Color c2, in double p) pure nothrow @safe @nogc { static if (is(Color == RGB)) return Color(cast(ubyte)(c1.r * p + c2.r * (1 - p)), cast(ubyte)(c1.g * p + c2.g * (1 - p)), cast(ubyte)(c1.b * p + c2.b * (1 - p))); else // This doesn't work for every kind of Color. return Color(cast(ubyte)(c1 * p + c2 * (1 - p))); }
// Plot function set here to handle the two cases of slope. void function(ref Image!Color, in int, in int, in double, in Color) pure nothrow @safe @nogc plot;
if (ax < ay) { swap(x1, y1); swap(x2, y2); swap(dx, dy); //plot = (img, x, y, p, col) { plot = (ref img, x, y, p, col) { assert(p >= 0.0 && p <= 1.0); img[y, x] = mixColors(col, img[y, x], p); }; } else { //plot = (img, x, y, p, col) { plot = (ref img, x, y, p, col) { assert(p >= 0.0 && p <= 1.0); img[x, y] = mixColors(col, img[x, y], p); }; }
if (x2 < x1) { swap(x1, x2); swap(y1, y2); } immutable gradient = dy / dx;
// Handle first endpoint. auto xEnd = round(x1); auto yEnd = y1 + gradient * (xEnd - x1); auto xGap = rfpart(x1 + 0.5); // This will be used in the main loop. immutable xpxl1 = cast(int)xEnd; immutable ypxl1 = cast(int)yEnd.floor; plot(img, xpxl1, ypxl1, rfpart(yEnd) * xGap, color); plot(img, xpxl1, ypxl1 + 1, fpart(yEnd) * xGap, color); // First y-intersection for the main loop. auto yInter = yEnd + gradient;
// Handle second endpoint. xEnd = round(x2); yEnd = y2 + gradient * (xEnd - x2); xGap = fpart(x2 + 0.5); // This will be used in the main loop. immutable xpxl2 = cast(int)xEnd; immutable ypxl2 = cast(int)yEnd.floor; plot(img, xpxl2, ypxl2, rfpart(yEnd) * xGap, color); plot(img, xpxl2, ypxl2 + 1, fpart(yEnd) * xGap, color);
// Main loop. foreach (immutable x; xpxl1 + 1 .. xpxl2) { plot(img, x, cast(int)yInter.floor, rfpart(yInter), color); plot(img, x, cast(int)yInter.floor + 1, fpart(yInter), color); yInter += gradient; }
}
void main() {
auto im1 = new Image!Gray(400, 300); im1.clear(Gray.white); im1.aaLine(7.4, 12.3, 307, 122.5, Gray.black); im1.aaLine(177.4, 12.3, 127, 222.5, Gray.black); im1.savePGM("xiaolin_lines1.pgm");
auto im2 = new Image!RGB(400, 300); im2.clear(RGB(0, 255, 0)); immutable red = RGB(255, 0, 0); im2.aaLine(7.4, 12.3, 307, 122.5, red); im2.aaLine(177.4, 12.3, 127, 222.5, red); im2.savePPM6("xiaolin_lines2.ppm");
}</lang>
FreeBASIC
This implementation follows the pseudocode given on Wikipedia. Only changed xend=round() in xend=ipart() to make it more in line with FreeBASIC's own line drawing routine. Rfpart give me some trouble so I changed if somewhat. The small functions where all converted into macro's <lang FreeBASIC>' version 21-06-2015 ' compile with: fbc -s console or fbc -s gui ' Xiaolin Wu’s line-drawing algorithm 'shared var and macro's
Dim Shared As UInteger wu_color
- Macro ipart(x)
Int(x) ' integer part
- EndMacro
- Macro round(x)
Int((x) + .5) ' round off
- EndMacro
- Macro fpart(x)
Frac(x) ' fractional part
- EndMacro
- Macro rfpart(x)
' 1 - Frac(x) ' seems to give problems for very small x IIf(1 - Frac(x) >= 1, 1, 1 - Frac(x))
- EndMacro
- Macro plot(x, y , c)
' use the alpha channel to set the amount of color PSet(x,y), wu_color Or (Int(c * 255)) Shl 24
- EndMacro
Sub drawline(x0 As Single, y0 As Single, x1 As Single, y1 As Single,_
col As UInteger = RGB(255,255,255))
wu_color = col And &HFFFFFF ' strip off the alpha channel information
Dim As Single gradient Dim As Single xend, yend, xgap, intery Dim As UInteger xpxl1, ypxl1, xpxl2, ypxl2, x Dim As Integer steep = Abs(y1 - y0) > Abs(x1 - x0) ' boolean
If steep Then Swap x0, y0 Swap x1, y1 End If
If x0 > x1 Then Swap x0, x1 Swap y0, y1 End If
gradient = (y1 - y0) / (x1 - x0)
' first endpoint ' xend = round(x0) xend = ipart(x0) yend = y0 + gradient * (xend - x0) xgap = rfpart(x0 + .5) xpxl1 = xend ' this will be used in the main loop ypxl1 = ipart(yend) If steep Then plot(ypxl1, xpxl1, rfpart(yend) * xgap) plot(ypxl1+1, xpxl1, fpart(yend) * xgap) Else plot(xpxl1, ypxl1, rfpart(yend) * xgap) plot(xpxl1, ypxl1+1, fpart(yend) * xgap) End If intery = yend + gradient ' first y-intersecction for the main loop
' handle second endpoint ' xend = round(x1) xend = ipart(x1) yend = y1 + gradient * (xend - x1) xgap = fpart(x1 + .5) xpxl2 = xend ' this will be used in the main loop ypxl2 = ipart(yend) If steep Then plot(ypxl2, xpxl2, rfpart(yend) * xgap) plot(ypxl2+1, xpxl2, fpart(yend) * xgap) Else plot(xpxl2, ypxl2, rfpart(yend) * xgap) plot(xpxl2, ypxl2+1, fpart(yend) * xgap) End If
' main loop If steep Then For x = xpxl1 + 1 To xpxl2 - 1 plot(ipart(intery), x, rfpart(intery)) plot(ipart(intery)+1, x, fpart(intery)) intery = intery + gradient Next Else For x = xpxl1 + 1 To xpxl2 - 1 plot(x, ipart(intery), rfpart(intery)) plot(x, ipart(intery)+1, fpart(intery)) intery = intery + gradient Next End If
End Sub
' ------=< MAIN >=------
- Define W_ 600
- Define H_ 600
- Include Once "fbgfx.bi" ' needed setting the screen attributes
Dim As Integer i Dim As String fname = __FILE__
ScreenRes W_, H_, 32,, FB.GFX_ALPHA_PRIMITIVES
Randomize Timer
For i = 0 To H_ Step H_\30
drawline(0, 0, W_, i, Int(Rnd * &HFFFFFF))
Next
For i = 0 To W_ Step W_\30
drawline(0, 0, i, H_, Int(Rnd * &HFFFFFF))
Next
i = InStr(fname,".bas") fname = Left(fname, Len(fname)-i+1) WindowTitle fname + " hit any key to end program"
While Inkey <> "" : Wend Sleep End</lang>
Go
<lang go>package raster
import "math"
func ipart(x float64) float64 {
return math.Floor(x)
}
func round(x float64) float64 {
return ipart(x + .5)
}
func fpart(x float64) float64 {
return x - ipart(x)
}
func rfpart(x float64) float64 {
return 1 - fpart(x)
}
// AaLine plots anti-aliased line by Xiaolin Wu's line algorithm. func (g *Grmap) AaLine(x1, y1, x2, y2 float64) {
// straight translation of WP pseudocode dx := x2 - x1 dy := y2 - y1 ax := dx if ax < 0 { ax = -ax } ay := dy if ay < 0 { ay = -ay } // plot function set here to handle the two cases of slope var plot func(int, int, float64) if ax < ay { x1, y1 = y1, x1 x2, y2 = y2, x2 dx, dy = dy, dx plot = func(x, y int, c float64) { g.SetPx(y, x, uint16(c*math.MaxUint16)) } } else { plot = func(x, y int, c float64) { g.SetPx(x, y, uint16(c*math.MaxUint16)) } } if x2 < x1 { x1, x2 = x2, x1 y1, y2 = y2, y1 } gradient := dy / dx
// handle first endpoint xend := round(x1) yend := y1 + gradient*(xend-x1) xgap := rfpart(x1 + .5) xpxl1 := int(xend) // this will be used in the main loop ypxl1 := int(ipart(yend)) plot(xpxl1, ypxl1, rfpart(yend)*xgap) plot(xpxl1, ypxl1+1, fpart(yend)*xgap) intery := yend + gradient // first y-intersection for the main loop
// handle second endpoint xend = round(x2) yend = y2 + gradient*(xend-x2) xgap = fpart(x2 + 0.5) xpxl2 := int(xend) // this will be used in the main loop ypxl2 := int(ipart(yend)) plot(xpxl2, ypxl2, rfpart(yend)*xgap) plot(xpxl2, ypxl2+1, fpart(yend)*xgap)
// main loop for x := xpxl1 + 1; x <= xpxl2-1; x++ { plot(x, int(ipart(intery)), rfpart(intery)) plot(x, int(ipart(intery))+1, fpart(intery)) intery = intery + gradient }
}</lang> Demonstration program: <lang go>package main
// Files required to build supporting package raster are found in: // * This task (immediately above) // * Bitmap // * Grayscale image // * Write a PPM file
import "raster"
func main() {
g := raster.NewGrmap(400, 300) g.AaLine(7.4, 12.3, 307, 122.5) g.AaLine(177.4, 12.3, 127, 222.5) g.Bitmap().WritePpmFile("wu.ppm")
}</lang>
J
Solution: <lang j>load'gl2' coinsert'jgl2'
drawpt=:4 :0"0 1
glrgb <.(-.x)*255 255 255 glpixel y
)
drawLine=:3 :0 NB. drawline x1,y1,x2,y2
pts=. 2 2$y isreversed=. </ |d=. -~/pts r=. |.^:isreversed"1 pts=. /:~ pts \:"1 |d gradient=. %~/ (\:|)d
'x y'=. |:pts xend=. <.0.5+ x yend=. y + gradient* xend-x xgap=. -.1|x+0.5
n=. i. >: -~/ xend 'xlist ylist'=. (n*/~1,gradient) + ({.xend),({.yend) weights=. ((2&}.,~ xgap*2&{.)&.(_1&|.) (,.~-.) 1|ylist) weights (drawpt r)"1 2 (,:+&0 1)"1 xlist,.<.ylist
)</lang>
Example use: <lang j> wd'pc win closeok; xywh 0 0 300 200;cc g isigraph; pas 0 0; pshow;' NB. J6 or earlier
wd'pc win closeok; minwh 600 400;cc g isidraw flush; pshow;' NB. J802 or later glpaint glclear glpaint drawLine 10 10 590 390</lang>
Java
<lang java>import java.awt.*; import static java.lang.Math.*; import javax.swing.*;
public class XiaolinWu extends JPanel {
public XiaolinWu() { Dimension dim = new Dimension(640, 640); setPreferredSize(dim); setBackground(Color.white); }
void plot(Graphics2D g, double x, double y, double c) { g.setColor(new Color(0f, 0f, 0f, (float)c)); g.fillOval((int) x, (int) y, 2, 2); }
int ipart(double x) { return (int) x; }
double fpart(double x) { return x - floor(x); }
double rfpart(double x) { return 1.0 - fpart(x); }
void drawLine(Graphics2D g, double x0, double y0, double x1, double y1) {
boolean steep = abs(y1 - y0) > abs(x1 - x0); if (steep) drawLine(g, y0, x0, y1, x1);
if (x0 > x1) drawLine(g, x1, y1, x0, y0);
double dx = x1 - x0; double dy = y1 - y0; double gradient = dy / dx;
// handle first endpoint double xend = round(x0); double yend = y0 + gradient * (xend - x0); double xgap = rfpart(x0 + 0.5); double xpxl1 = xend; // this will be used in the main loop double ypxl1 = ipart(yend);
if (steep) { plot(g, ypxl1, xpxl1, rfpart(yend) * xgap); plot(g, ypxl1 + 1, xpxl1, fpart(yend) * xgap); } else { plot(g, xpxl1, ypxl1, rfpart(yend) * xgap); plot(g, xpxl1, ypxl1 + 1, fpart(yend) * xgap); }
// first y-intersection for the main loop double intery = yend + gradient;
// handle second endpoint xend = round(x1); yend = y1 + gradient * (xend - x1); xgap = fpart(x1 + 0.5); double xpxl2 = xend; // this will be used in the main loop double ypxl2 = ipart(yend);
if (steep) { plot(g, ypxl2, xpxl2, rfpart(yend) * xgap); plot(g, ypxl2 + 1, xpxl2, fpart(yend) * xgap); } else { plot(g, xpxl2, ypxl2, rfpart(yend) * xgap); plot(g, xpxl2, ypxl2 + 1, fpart(yend) * xgap); }
// main loop for (double x = xpxl1 + 1; x <= xpxl2 - 1; x++) { if (steep) { plot(g, ipart(intery), x, rfpart(intery)); plot(g, ipart(intery) + 1, x, fpart(intery)); } else { plot(g, x, ipart(intery), rfpart(intery)); plot(g, x, ipart(intery) + 1, fpart(intery)); } intery = intery + gradient; } }
@Override public void paintComponent(Graphics gg) { super.paintComponent(gg); Graphics2D g = (Graphics2D) gg;
drawLine(g, 550, 170, 50, 435); }
public static void main(String[] args) { SwingUtilities.invokeLater(() -> { JFrame f = new JFrame(); f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); f.setTitle("Xiaolin Wu's line algorithm"); f.setResizable(false); f.add(new XiaolinWu(), BorderLayout.CENTER); f.pack(); f.setLocationRelativeTo(null); f.setVisible(true); }); }
}</lang>
Kotlin
<lang scala>// version 1.1.2
import java.awt.* import javax.swing.*
class XiaolinWu: JPanel() {
init { preferredSize = Dimension(640, 640) background = Color.white }
private fun plot(g: Graphics2D, x: Double, y: Double, c: Double) { g.color = Color(0f, 0f, 0f, c.toFloat()) g.fillOval(x.toInt(), y.toInt(), 2, 2) }
private fun ipart(x: Double) = x.toInt()
private fun fpart(x: Double) = x - Math.floor(x)
private fun rfpart(x: Double) = 1.0 - fpart(x)
private fun drawLine(g: Graphics2D, x0: Double, y0: Double, x1: Double, y1: Double) { val steep = Math.abs(y1 - y0) > Math.abs(x1 - x0) if (steep) drawLine(g, y0, x0, y1, x1) if (x0 > x1) drawLine(g, x1, y1, x0, y0)
val dx = x1 - x0 val dy = y1 - y0 val gradient = dy / dx
// handle first endpoint var xend = Math.round(x0).toDouble() var yend = y0 + gradient * (xend - x0) var xgap = rfpart(x0 + 0.5) val xpxl1 = xend // this will be used in the main loop val ypxl1 = ipart(yend).toDouble()
if (steep) { plot(g, ypxl1, xpxl1, rfpart(yend) * xgap) plot(g, ypxl1 + 1.0, xpxl1, fpart(yend) * xgap) } else { plot(g, xpxl1, ypxl1, rfpart(yend) * xgap) plot(g, xpxl1, ypxl1 + 1.0, fpart(yend) * xgap) }
// first y-intersection for the main loop var intery = yend + gradient
// handle second endpoint xend = Math.round(x1).toDouble() yend = y1 + gradient * (xend - x1) xgap = fpart(x1 + 0.5) val xpxl2 = xend // this will be used in the main loop val ypxl2 = ipart(yend).toDouble()
if (steep) { plot(g, ypxl2, xpxl2, rfpart(yend) * xgap) plot(g, ypxl2 + 1.0, xpxl2, fpart(yend) * xgap) } else { plot(g, xpxl2, ypxl2, rfpart(yend) * xgap) plot(g, xpxl2, ypxl2 + 1.0, fpart(yend) * xgap) }
// main loop var x = xpxl1 + 1.0 while (x <= xpxl2 - 1) { if (steep) { plot(g, ipart(intery).toDouble(), x, rfpart(intery)) plot(g, ipart(intery).toDouble() + 1.0, x, fpart(intery)) } else { plot(g, x, ipart(intery).toDouble(), rfpart(intery)) plot(g, x, ipart(intery).toDouble() + 1.0, fpart(intery)) } intery += gradient x++ } }
override protected fun paintComponent(gg: Graphics) { super.paintComponent(gg) val g = gg as Graphics2D drawLine(g, 550.0, 170.0, 50.0, 435.0) }
}
fun main(args: Array<String>) {
SwingUtilities.invokeLater { val f = JFrame() f.defaultCloseOperation = JFrame.EXIT_ON_CLOSE f.title = "Xiaolin Wu's line algorithm" f.isResizable = false f.add(XiaolinWu(), BorderLayout.CENTER) f.pack() f.setLocationRelativeTo(null) f.isVisible = true }
}</lang>
Liberty BASIC
<lang lb> NoMainWin WindowWidth = 270 WindowHeight = 290 UpperLeftX=int((DisplayWidth-WindowWidth)/2) UpperLeftY=int((DisplayHeight-WindowHeight)/2)
Global variablesInitialized : variablesInitialized = 0 Global BackColor$ : BackColor$ = "0 0 0" ' BackColor$ = "255 255 255"
'now, right click randomizes BG
Global size : size = 1'4 global mousepoints.mouseX0, mousepoints.mouseY0, mousepoints.mouseX1, mousepoints.mouseY1
'StyleBits #main.gbox, 0, _WS_BORDER, 0, 0 GraphicBox #main.gbox, 0, 0, 253, 252
Open "Click Twice to Form Line" For Window As #main Print #main, "TrapClose quit" Print #main.gbox, "Down; Color Black" Print #main.gbox, "Down; fill ";BackColor$ Print #main.gbox, "When leftButtonUp gBoxClick" Print #main.gbox, "When rightButtonUp RandomBG" Print #main.gbox, "Size "; size
result = drawAntiAliasedLine(126.5, 0, 126.5, 252, "255 0 0") result = drawAntiAliasedLine(0, 126, 253, 126, "255 0 0") result = drawAntiAliasedLine(0, 0, 253, 252, "255 0 0") result = drawAntiAliasedLine(253, 0, 0, 252, "255 0 0") Wait
Sub quit handle$ Close #main End End Sub
sub RandomBG handle$, MouseX, MouseY
BackColor$ = int(rnd(1)*256);" ";int(rnd(1)*256);" ";int(rnd(1)*256) Print #main.gbox, "CLS; fill ";BackColor$ variablesInitialized = 0
end sub
Sub gBoxClick handle$, MouseX, MouseY 'We will use the mousepoints "struct" to hold the values 'that way they are retained between subroutine calls If variablesInitialized = 0 Then Print #main.gbox, "CLS; fill ";BackColor$ mousepoints.mouseX0 = MouseX mousepoints.mouseY0 = MouseY variablesInitialized = 1 Else If variablesInitialized = 1 Then mousepoints.mouseX1 = MouseX mousepoints.mouseY1 = MouseY variablesInitialized = 0 result = drawAntiAliasedLine(mousepoints.mouseX0, mousepoints.mouseY0, mousepoints.mouseX1, mousepoints.mouseY1, "255 0 0") End If End If End Sub
Function Swap(Byref a,Byref b) aTemp = b b = a a = aTemp End Function
Function RoundtoInt(val) RoundtoInt = Int(val + 0.5) End Function
Function PlotAntiAliased(x, y, RGB$, b, steep)
RGB$ = Int(Val(Word$(BackColor$, 1))*(1-b) + Val(Word$(RGB$, 1)) * b) ; " " ; _ Int(Val(Word$(BackColor$, 2))*(1-b) + Val(Word$(RGB$, 3)) * b) ; " " ; _ Int(Val(Word$(BackColor$, 3))*(1-b) + Val(Word$(RGB$, 2)) * b)
if steep then 'x and y reversed Print #main.gbox, "Down; Color " + RGB$ + "; Set " + str$(y) + " " + str$(x) else Print #main.gbox, "Down; Color " + RGB$ + "; Set " + str$(x) + " " + str$(y) end if End Function
Function fracPart(x) fracPart = (x Mod 1) End function
Function invFracPart(x) invFracPart = (1 - fracPart(x)) End Function
Function drawAntiAliasedLine(x1, y1, x2, y2, RGB$) If (x2 - x1)=0 Or (y2 - y1)=0 Then Print #main.gbox, "Down; Color " + RGB$ result = BresenhamLine(x1, y1, x2, y2) Exit Function End If steep = abs(x2 - x1) < abs(y2 - y1) if steep then 'x and y should be reversed result = Swap(x1, y1) result = Swap(x2, y2) end if
If (x2 < x1) Then result = Swap(x1, x2) result = Swap(y1, y2) End If dx = (x2 - x1) dy = (y2 - y1) grad = (dy/ dx) 'Handle the First EndPoint xend = RoundtoInt(x1) yend = y1 + grad * (xend - x1) xgap = invFracPart(x1 + 0.5) ix1 = xend iy1 = Int(yend) result = PlotAntiAliased(ix1, iy1, RGB$, invFracPart(yend) * xgap, steep ) result = PlotAntiAliased(ix1, (iy1 + size), RGB$, fracPart(yend) * xgap, steep ) yf = (yend + grad) 'Handle the Second EndPoint xend = RoundtoInt(x2) yend = y2 + grad * (xend - x2) xgap = fracPart(x2 + 0.5) ix2 = xend iy2 = Int(yend) result = PlotAntiAliased(ix2, iy2, RGB$, invFracPart(yend) * xgap, steep ) result = PlotAntiAliased(ix2, (iy2 + size), RGB$, fracPart(yend) * xgap, steep ) For x = ix1 + 1 To ix2 - 1 result = PlotAntiAliased(x, Int(yf), RGB$, invFracPart(yf), steep ) result = PlotAntiAliased(x, (Int(yf) + size), RGB$, fracPart(yf), steep ) yf = (yf + grad) Next x End Function
Function BresenhamLine(x0, y0, x1, y1) dx = Abs(x1 - x0) dy = Abs(y1 - y0) sx = ((x1 > x0) + Not(x0 < x1)) sy = ((y1 > y0) + Not(y0 < y1)) errornum = (dx - dy) Do While 1 Print #main.gbox, "Set " + str$(x0) + " " + str$(y0) If (x0 = x1) And (y0 = y1) Then Exit Do errornum2 = (2 * errornum) If errornum2 > (-1 * dy) Then errornum = (errornum - dy) x0 = (x0 + sx) End If If errornum2 < dx Then errornum = (errornum + dx) y0 = (y0 + sy) End If Loop End Function
</lang>
Pascal
Based on Wikipwdia pseudocode with some optimizations and alpha handling.
<lang pascal> program wu; uses
SDL2, math;
const
FPS = 1000 div 60; SCALE = 6;
var
win: PSDL_Window; ren: PSDL_Renderer; mouse_x, mouse_y: longint; origin: TSDL_Point; event: TSDL_Event; line_alpha: byte = 255;
procedure SDL_RenderDrawWuLine(renderer: PSDL_Renderer; x1, y1, x2, y2: longint); var
r, g, b, a, a_new: Uint8; gradient, iy: real; x, y: longint; px, py: plongint;
procedure swap(var a, b: longint); var tmp: longint; begin tmp := a; a := b; b := tmp; end;
begin
if a = 0 then exit; SDL_GetRenderDrawColor(renderer, @r, @g, @b, @a); if abs(y2 - y1) > abs(x2 - x1) then begin swap(x1, y1); swap(x2, y2); px := @y; py := @x; end else begin px := @x; py := @y; end; if x1 > x2 then begin swap(x1, x2); swap(y1, y2); end; x := x2 - x1; if x = 0 then x := 1; gradient := (y2 - y1) / x; iy := y1; for x := x1 to x2 do begin a_new := round(a * frac(iy)); y := floor(iy); SDL_SetRenderDrawColor(renderer, r, g, b, a-a_new); SDL_RenderDrawPoint(renderer, px^, py^); inc(y); SDL_SetRenderDrawColor(renderer, r, g, b, a_new); SDL_RenderDrawPoint(renderer, px^, py^); iy := iy + gradient; end; SDL_SetRenderDrawColor(renderer, r, g, b, a);
end;
begin
SDL_Init(SDL_INIT_VIDEO); win := SDL_CreateWindow('Xiaolin Wus line algorithm', SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED, 640, 480, SDL_WINDOW_RESIZABLE); ren := SDL_CreateRenderer(win, -1, 0); if ren = NIL then begin writeln(SDL_GetError); halt; end; SDL_SetRenderDrawBlendMode(ren, SDL_BLENDMODE_BLEND); SDL_RenderSetScale(ren, SCALE, SCALE); SDL_SetCursor(SDL_CreateSystemCursor(SDL_SYSTEM_CURSOR_CROSSHAIR));
mouse_x := 0; mouse_y := 0; origin.x := 0; origin.y := 0; repeat while SDL_PollEvent(@event) = 1 do case event.type_ of SDL_KEYDOWN: if event.key.keysym.sym = SDLK_ESCAPE then halt; SDL_MOUSEBUTTONDOWN: begin origin.x := mouse_x; origin.y := mouse_y; end; SDL_MOUSEMOTION: with event.motion do begin mouse_x := x div SCALE; mouse_y := y div SCALE; end; SDL_MOUSEWHEEL: line_alpha := EnsureRange(line_alpha + event.wheel.y * 20, 0, 255); SDL_QUITEV: halt; end;
SDL_SetRenderDrawColor(ren, 35, 35, 35, line_alpha); SDL_RenderDrawWuLine(ren, origin.x, origin.y, mouse_x, mouse_y); SDL_RenderPresent(ren); SDL_SetRenderDrawColor(ren, 255, 255, 255, 255); SDL_RenderClear(ren); SDL_Delay(FPS); until false;
end. </lang>
Perl
This is mostly a translation of the pseudo-code on Wikipedia, except that the $plot trick was inspired by the perl6 RosettaCode example. <lang perl>#!perl use strict; use warnings;
sub plot { my ($x, $y, $c) = @_; printf "plot %d %d %.1f\n", $x, $y, $c if $c; }
sub ipart { int shift; }
sub round { int( 0.5 + shift ); }
sub fpart { my $x = shift; $x - int $x; }
sub rfpart { 1 - fpart(shift); }
sub drawLine { my ($x0, $y0, $x1, $y1) = @_;
my $plot = \&plot;
if( abs($y1 - $y0) > abs($x1 - $x0) ) { $plot = sub { plot( @_[1, 0, 2] ) }; ($x0, $y0, $x1, $y1) = ($y0, $x0, $y1, $x1); }
if( $x0 > $x1 ) { ($x0, $x1, $y0, $y1) = ($x1, $x0, $y1, $y0); }
my $dx = $x1 - $x0; my $dy = $y1 - $y0; my $gradient = $dy / $dx;
my @xends; my $intery;
# handle the endpoints for my $xy ([$x0, $y0], [$x1, $y1]) { my ($x, $y) = @$xy; my $xend = round($x); my $yend = $y + $gradient * ($xend - $x); my $xgap = rfpart($x + 0.5);
my $x_pixel = $xend; my $y_pixel = ipart($yend); push @xends, $x_pixel;
$plot->($x_pixel, $y_pixel , rfpart($yend) * $xgap); $plot->($x_pixel, $y_pixel+1, fpart($yend) * $xgap); next if defined $intery; # first y-intersection for the main loop $intery = $yend + $gradient; }
# main loop
for my $x ( $xends[0] + 1 .. $xends[1] - 1 ) { $plot->($x, ipart ($intery), rfpart($intery)); $plot->($x, ipart ($intery)+1, fpart($intery)); $intery += $gradient; } }
if( $0 eq __FILE__ ) { drawLine( 0, 1, 10, 2 ); } __END__ </lang>
- Output:
plot 0 1 0.5 plot 10 2 0.5 plot 1 1 0.9 plot 1 2 0.1 plot 2 1 0.8 plot 2 2 0.2 plot 3 1 0.7 plot 3 2 0.3 plot 4 1 0.6 plot 4 2 0.4 plot 5 1 0.5 plot 5 2 0.5 plot 6 1 0.4 plot 6 2 0.6 plot 7 1 0.3 plot 7 2 0.7 plot 8 1 0.2 plot 8 2 0.8 plot 9 1 0.1 plot 9 2 0.9
Perl 6
<lang perl6>sub plot(\x, \y, \c) { say "plot {x} {y} {c}" }
sub fpart(\x) { x - floor(x) }
sub draw-line(@a is copy, @b is copy) {
my Bool \steep = abs(@b[1] - @a[1]) > abs(@b[0] - @a[0]); my $plot = &OUTER::plot; if steep {
$plot = -> $y, $x, $c { plot($x, $y, $c) } @a.=reverse; @b.=reverse;
} if @a[0] > @b[0] { my @t = @a; @a = @b; @b = @t }
my (\x0,\y0) = @a; my (\x1,\y1) = @b; my \dx = x1 - x0; my \dy = y1 - y0; my \gradient = dy / dx; # handle first endpoint my \x-end1 = round(x0); my \y-end1 = y0 + gradient * (x-end1 - x0); my \x-gap1 = 1 - round(x0 + 0.5);
my \x-pxl1 = x-end1; # this will be used in the main loop my \y-pxl1 = floor(y-end1); my \c1 = fpart(y-end1) * x-gap1;
$plot(x-pxl1, y-pxl1 , 1 - c1) unless c1 == 1; $plot(x-pxl1, y-pxl1 + 1, c1 ) unless c1 == 0; # handle second endpoint my \x-end2 = round(x1); my \y-end2 = y1 + gradient * (x-end2 - x1); my \x-gap2 = fpart(x1 + 0.5);
my \x-pxl2 = x-end2; # this will be used in the main loop my \y-pxl2 = floor(y-end2); my \c2 = fpart(y-end2) * x-gap2; my \intery = y-end1 + gradient;
# main loop for (x-pxl1 + 1 .. x-pxl2 - 1)
Z (intery, intery + gradient ... *)
-> (\x,\y) {
my \c = fpart(y); $plot(x, floor(y) , 1 - c) unless c == 1; $plot(x, floor(y) + 1, c ) unless c == 0;
}
$plot(x-pxl2, y-pxl2 , 1 - c2) unless c2 == 1; $plot(x-pxl2, y-pxl2 + 1, c2 ) unless c2 == 0;
}
draw-line [0,1], [10,2];</lang>
- Output:
plot 0 1 1 plot 1 1 0.9 plot 1 2 0.1 plot 2 1 0.8 plot 2 2 0.2 plot 3 1 0.7 plot 3 2 0.3 plot 4 1 0.6 plot 4 2 0.4 plot 5 1 0.5 plot 5 2 0.5 plot 6 1 0.4 plot 6 2 0.6 plot 7 1 0.3 plot 7 2 0.7 plot 8 1 0.2 plot 8 2 0.8 plot 9 1 0.1 plot 9 2 0.9 plot 10 2 1
Phix
For educational/comparison purposes only: see demo\pGUI\aaline.exw for a much shorter version.
Resize the window to show lines at any angle
<lang Phix>-- -- demo\rosetta\XiaolinWuLine.exw -- ============================== -- constant TITLE = "Xiaolin Wu's line algorithm"
bool bresline = false -- space toggles, for comparison
include pGUI.e
Ihandle dlg, canvas cdCanvas cddbuffer, cdcanvas
constant BACK = CD_PARCHMENT,
LINE = CD_BLUE, rB = red(BACK), gB = green(BACK), bB = blue(BACK), rL = red(LINE), gL = green(LINE), bL = blue(LINE)
procedure plot(atom x, atom y, atom c, bool steep=false) -- plot the pixel at (x, y) with brightness c (where 0 <= c <= 1)
if steep then {x,y} = {y,x} end if atom C = 1-c c = rgb(rL*c+rB*C,gL*c+gB*C,bL*c+bB*C) cdCanvasPixel(cddbuffer, x, y, c)
end procedure
procedure plot2(atom x, atom y, atom f, atom xgap, bool steep)
plot(x,y,(1-f)*xgap,steep) plot(x,y+1,f*xgap,steep)
end procedure
function fpart(atom x)
return x - floor(x) -- fractional part of x
end function
procedure draw_line(atom x0,y0,x1,y1)
if bresline then cdCanvasLine(cddbuffer, x0, y0, x1, y1) return end if bool steep := abs(y1 - y0) > abs(x1 - x0) if steep then {x0, y0, x1, y1} = {y0, x0, y1, x1} end if if x0>x1 then {x0, x1, y0, y1} = {x1, x0, y1, y0} end if atom dx := x1 - x0, dy := y1 - y0, gradient := iff(dx=0? 1 : dy / dx)
-- handle first endpoint atom xend := round(x0), yend := y0 + gradient * (xend - x0), xgap := 1-fpart(x0 + 0.5), xpxl1 := xend, -- this will be used in the main loop ypxl1 := floor(yend) plot2(xpxl1, ypxl1, fpart(yend), xgap, steep) atom intery := yend + gradient -- first y-intersection for the main loop -- handle second endpoint xend := round(x1) yend := y1 + gradient * (xend - x1) xgap := fpart(x1 + 0.5) atom xpxl2 := xend, -- this will be used in the main loop ypxl2 := floor(yend) plot2(xpxl2, ypxl2, fpart(yend), xgap, steep) -- main loop for x = xpxl1+1 to xpxl2-1 do plot2(x, floor(intery), fpart(intery), 1, steep) intery += gradient end for
end procedure
function redraw_cb(Ihandle /*ih*/, integer /*posx*/, integer /*posy*/)
integer {w, h} = sq_sub(IupGetIntInt(canvas, "DRAWSIZE"),10) cdCanvasActivate(cddbuffer) cdCanvasClear(cddbuffer) draw_line(0,0,200,200) draw_line(w,0,200,200) draw_line(0,h,200,200) draw_line(w,h,200,200) cdCanvasFlush(cddbuffer) return IUP_DEFAULT
end function
function map_cb(Ihandle ih)
cdcanvas = cdCreateCanvas(CD_IUP, ih) cddbuffer = cdCreateCanvas(CD_DBUFFER, cdcanvas) cdCanvasSetBackground(cddbuffer, BACK) cdCanvasSetForeground(cddbuffer, LINE) return IUP_DEFAULT
end function
function esc_close(Ihandle /*ih*/, atom c)
if c=K_ESC then return IUP_CLOSE end if if c=' ' then bresline = not bresline IupRedraw(canvas) end if return IUP_CONTINUE
end function
procedure main()
IupOpen() canvas = IupCanvas(NULL) IupSetAttribute(canvas, "RASTERSIZE", "640x480") IupSetCallback(canvas, "MAP_CB", Icallback("map_cb")) IupSetCallback(canvas, "ACTION", Icallback("redraw_cb")) dlg = IupDialog(canvas) IupSetAttribute(dlg, "TITLE", TITLE) IupSetCallback(dlg, "K_ANY", Icallback("esc_close")) IupShow(dlg) IupSetAttribute(canvas, "RASTERSIZE", NULL) IupMainLoop() IupClose()
end procedure main()</lang>
PicoLisp
<lang PicoLisp>(scl 2)
(de plot (Img X Y C)
(set (nth Img (*/ Y 1.0) (*/ X 1.0)) (- 100 C)) )
(de ipart (X)
(* 1.0 (/ X 1.0)) )
(de iround (X)
(ipart (+ X 0.5)) )
(de fpart (X)
(% X 1.0) )
(de rfpart (X)
(- 1.0 (fpart X)) )
(de xiaolin (Img X1 Y1 X2 Y2)
(let (DX (- X2 X1) DY (- Y2 Y1)) (use (Grad Xend Yend Xgap Xpxl1 Ypxl1 Xpxl2 Ypxl2 Intery) (when (> (abs DY) (abs DX)) (xchg 'X1 'Y1 'X2 'Y2) ) (when (> X1 X2) (xchg 'X1 'X2 'Y1 'Y2) ) (setq Grad (*/ DY 1.0 DX) Xend (iround X1) Yend (+ Y1 (*/ Grad (- Xend X1) 1.0)) Xgap (rfpart (+ X1 0.5)) Xpxl1 Xend Ypxl1 (ipart Yend) ) (plot Img Xpxl1 Ypxl1 (*/ (rfpart Yend) Xgap 1.0)) (plot Img Xpxl1 (+ 1.0 Ypxl1) (*/ (fpart Yend) Xgap 1.0)) (setq Intery (+ Yend Grad) Xend (iround X2) Yend (+ Y2 (*/ Grad (- Xend X2) 1.0)) Xgap (fpart (+ X2 0.5)) Xpxl2 Xend Ypxl2 (ipart Yend) ) (plot Img Xpxl2 Ypxl2 (*/ (rfpart Yend) Xgap 1.0)) (plot Img Xpxl2 (+ 1.0 Ypxl2) (*/ (fpart Yend) Xgap 1.0)) (for (X (+ Xpxl1 1.0) (>= (- Xpxl2 1.0) X) (+ X 1.0)) (plot Img X (ipart Intery) (rfpart Intery)) (plot Img X (+ 1.0 (ipart Intery)) (fpart Intery)) (inc 'Intery Grad) ) ) ) )
(let Img (make (do 90 (link (need 120 99)))) # Create image 120 x 90
(xiaolin Img 10.0 10.0 110.0 80.0) # Draw lines (xiaolin Img 10.0 10.0 110.0 45.0) (xiaolin Img 10.0 80.0 110.0 45.0) (xiaolin Img 10.0 80.0 110.0 10.0) (out "img.pgm" # Write to bitmap file (prinl "P2") (prinl 120 " " 90) (prinl 100) (for Y Img (apply printsp Y)) ) )</lang>
PureBasic
<lang PureBasic>Macro PlotB(x, y, Color, b)
Plot(x, y, RGB(Red(Color) * (b), Green(Color) * (b), Blue(Color) * (b)))
EndMacro
Procedure.f fracPart(x.f)
ProcedureReturn x - Int(x)
EndProcedure
Procedure.f invFracPart(x.f)
ProcedureReturn 1.0 - fracPart(x)
EndProcedure
Procedure drawAntiAliasedLine(x1.f, y1.f, x2.f, y2.f, color)
Protected.f dx, dy, xend, yend, grad, yf, xgap, ix1, iy1, ix2, iy2 Protected x dx = x2 - x1 dy = y2 - y1 If Abs(dx) < Abs(dy) Swap x1, y1 Swap x2, y2 Swap dx, dy EndIf If x2 < x1 Swap x1, x2 Swap y1, y2 EndIf grad = dy / dx ;handle first endpoint xend = Round(x1, #pb_round_nearest) yend = y1 + grad * (xend - x1) xgap = invFracPart(x1 + 0.5) ix1 = xend ;this will be used in the MAIN loop iy1 = Int(yend) PlotB(ix1, iy1, color, invFracPart(yend) * xgap) PlotB(ix1, iy1 + 1, color, fracPart(yend) * xgap) yf = yend + grad ;first y-intersection for the MAIN loop ;handle second endpoint xend = Round(x2, #pb_round_nearest) yend = y2 + grad * (xend - x2) xgap = fracPart(x2 + 0.5) ix2 = xend ;this will be used in the MAIN loop iy2 = Int(yend) PlotB(ix2, iy2, color, invFracPart(yend) * xgap) PlotB(ix2, iy2 + 1, color, fracPart(yend) * xgap) ;MAIN loop For x = ix1 + 1 To ix2 - 1 PlotB(x, Int(yf), color, invFracPart(yf)) PlotB(x, Int(yf) + 1, color, fracPart(yf)) yf + grad Next
EndProcedure
Define w = 200, h = 200, img = 1 CreateImage(img, w, h) ;img is internal id of the image
OpenWindow(0, 0, 0, w, h,"Xiaolin Wu's line algorithm", #PB_Window_SystemMenu)
StartDrawing(ImageOutput(img))
drawAntiAliasedLine(80,20, 130,80, RGB(255, 0, 0))
StopDrawing()
ImageGadget(0, 0, 0, w, h, ImageID(img))
Define event Repeat
event = WaitWindowEvent()
Until event = #PB_Event_CloseWindow</lang>
Python
<lang python>"""Script demonstrating drawing of anti-aliased lines using Xiaolin Wu's line algorithm
usage: python xiaolinwu.py [output-file]
""" from __future__ import division import sys
from PIL import Image
def _fpart(x):
return x - int(x)
def _rfpart(x):
return 1 - _fpart(x)
def putpixel(img, xy, color, alpha=1):
"""Paints color over the background at the point xy in img. Use alpha for blending. alpha=1 means a completely opaque foreground.
""" c = tuple(map(lambda bg, fg: int(round(alpha * fg + (1-alpha) * bg)), img.getpixel(xy), color)) img.putpixel(xy, c)
def draw_line(img, p1, p2, color):
"""Draws an anti-aliased line in img from p1 to p2 with the given color.""" x1, y1, x2, y2 = p1 + p2 dx, dy = x2-x1, y2-y1 steep = abs(dx) < abs(dy) p = lambda px, py: ((px,py), (py,px))[steep]
if steep: x1, y1, x2, y2, dx, dy = y1, x1, y2, x2, dy, dx if x2 < x1: x1, x2, y1, y2 = x2, x1, y2, y1
grad = dy/dx intery = y1 + _rfpart(x1) * grad def draw_endpoint(pt): x, y = pt xend = round(x) yend = y + grad * (xend - x) xgap = _rfpart(x + 0.5) px, py = int(xend), int(yend) putpixel(img, (px, py), color, _rfpart(yend) * xgap) putpixel(img, (px, py+1), color, _fpart(yend) * xgap) return px
xstart = draw_endpoint(p(*p1)) + 1 xend = draw_endpoint(p(*p2))
for x in range(xstart, xend): y = int(intery) putpixel(img, p(x, y), color, _rfpart(intery)) putpixel(img, p(x, y+1), color, _fpart(intery)) intery += grad
if __name__ == '__main__':
if len(sys.argv) != 2: print 'usage: python xiaolinwu.py [output-file]' sys.exit(-1)
blue = (0, 0, 255) yellow = (255, 255, 0) img = Image.new("RGB", (500,500), blue) for a in range(10, 431, 60): draw_line(img, (10, 10), (490, a), yellow) draw_line(img, (10, 10), (a, 490), yellow) draw_line(img, (10, 10), (490, 490), yellow) filename = sys.argv[1] img.save(filename) print 'image saved to', filename</lang>
Racket
<lang racket>#lang racket (require 2htdp/image)
(define (plot img x y c)
(define c*255 (exact-round (* (- 1 c) 255))) (place-image (rectangle 1 1 'solid (make-color c*255 c*255 c*255 255)) x y img))
(define ipart exact-floor) ; assume that a "round-down" is what we want when -ve
- `round` is built in -- but we'll use exact round (and I'm not keen on over-binding round)
(define (fpart n) (- n (exact-floor n))) (define (rfpart n) (- 1 (fpart n)))
(define (draw-line img x0 y0 x1 y1)
(define (draw-line-steeped img x0 y0 x1 y1 steep?) (define (draw-line-steeped-l-to-r img x0 y0 x1 y1 steep?) (define dx (- x1 x0)) (define dy (- y1 y0)) (define gradient (/ dy dx)) (define (handle-end-point img x y) (define xend (exact-round x)) (define yend (+ y (* gradient (- xend x)))) (define xgap (rfpart (+ x 0.5))) (define ypxl (ipart yend)) (define intery (+ yend gradient)) (case steep? [(#t) (define img* (plot img ypxl xend (* xgap (rfpart yend)))) (values (plot img* (+ ypxl 1) xend (* xgap (fpart yend))) xend intery)] [(#f) (define img* (plot img xend ypxl (* xgap (rfpart yend)))) (values (plot img* xend (+ ypxl 1) (* xgap (fpart yend))) xend intery)])) (define-values (img-with-l-endpoint xpl1 intery) (handle-end-point img x0 y0)) (define-values (img-with-r-endpoint xpl2 _) (handle-end-point img-with-l-endpoint x1 y1)) (for/fold ((img img-with-l-endpoint) (y intery)) ((x (in-range (+ xpl1 1) xpl2))) (define y-i (ipart y)) (values (case steep? [(#t) (define img* (plot img y-i x (rfpart y))) (plot img* (+ 1 y-i) x (fpart y))] [(#f) (define img* (plot img x y-i (rfpart y))) (plot img* x (+ 1 y-i) (fpart y))]) (+ y gradient)))) (if (> x0 x1) (draw-line-steeped-l-to-r img x1 y1 x0 y0 steep?) (draw-line-steeped-l-to-r img x0 y0 x1 y1 steep?))) (define steep? (> (abs (- y1 y0)) (abs (- x1 x0)))) (define-values (img* _) (if steep? (draw-line-steeped img y0 x0 y1 x1 steep?) (draw-line-steeped img x0 y0 x1 y1 steep?))) img*)
(define img-1 (beside
(scale 3 (draw-line (empty-scene 150 100) 12 12 138 88)) (above (scale 1 (draw-line (empty-scene 150 100) 12 50 138 50)) (scale 1 (draw-line (empty-scene 150 100) 75 12 75 88)) (scale 1 (draw-line (empty-scene 150 100) 12 88 138 12)))))
(define img-2
(beside (scale 3 (draw-line (empty-scene 100 150) 12 12 88 138)) (above (scale 1 (draw-line (empty-scene 100 150) 50 12 50 138)) (scale 1 (draw-line (empty-scene 100 150) 12 75 88 75)) (scale 1 (draw-line (empty-scene 100 150) 88 12 12 138)))))
img-1 img-2 (save-image img-1 "images/xiaolin-wu-racket-1.png") (save-image img-2 "images/xiaolin-wu-racket-2.png")</lang>
Output files: File:Xiaolin-wu-racket-1.png File:Xiaolin-wu-racket-2.png
REXX
This REXX example uses the Xiaolin Wu line algorithm to draw a line (with output).
Apparently, there may be an error in the definition of the algorithm (which only manifests itself with negative numbers):
use of the IPART function should probably be FLOOR.
[See the talk section on the Xiaolin Wu's line algorithm.]
http://en.wikipedia.org/wiki/Talk:Xiaolin_Wu%27s_line_algorithm
Also, it takes in account (that can easily be overlooked) of the note after the description of the algorithm:
Note: If at the beginning of the routine abs(dx) < abs(dy) is true, then all plotting should be done with x and y reversed.
<lang rexx>/*REXX program plots/draws (ASCII) a line using the Xiaolin Wu line algorithm. */
background= '·' /*background character: a middle-dot. */
image.= background /*fill the array with middle-dots. */ plotC= '░▒▓█' /*characters used for plotting points. */ EoE= 3000 /*EOE = End Of Earth, er, ··· graph. */ do j=-EoE to +EoE /*define the graph: lowest ──► highest.*/ image.j.0= '─' /*define the graph's horizontal axis. */ image.0.j= '│' /* " " " verical " */ end /*j*/ image.0.0= '┼' /*define the graph's axis origin (char)*/
parse arg xi yi xf yf . /*allow specifying the line-end points.*/ if xi== | xi=="," then xi= 1 /*Not specified? Then use the default.*/ if yi== | yi=="," then yi= 2 /* " " " " " " */ if xf== | xf=="," then xf=11 /* " " " " " " */ if yf== | yf=="," then yf=12 /* " " " " " " */ minX=0; minY=0 /*use these as the limits for plotting.*/ maxX=0; maxY=0 /* " " " " " " " */ call drawLine xi, yi, xf, yf /*invoke subroutine and graph the line.*/ border=2 /*allow additional space (plot border).*/ minX=minX - border * 2; maxX=maxX+border * 2 /*preserve screen's aspect ratio {*2}.*/ minY=minY - border ; maxY=maxY+border
do y=maxY to minY by -1; _= /*construct a row.*/ do x=minX to maxX; _=_ || image.x.y; end /*x*/ say _ /*display the constructed row to term. */ end /*y*/ /*graph is cropped by the MINs and MAXs*/
exit /*stick a fork in it, we're all done. */ /*──────────────────────────────────────────────────────────────────────────────────────*/ drawLine: parse arg x1,y1,x2,y2; switchXY=0; dx=x2-x1
dy=y2-y1 if abs(dx)<abs(dy) then parse value x1 y1 x2 y2 dx dy with y1 x2 y2 x2 dy dx if x2<x1 then parse value x1 x2 y1 y2 1 with x2 x1 y2 y1 switchXY gradient=dy/dx xend=round(x1) /*◄─────────────────1st endpoint.══════════════*/ yend=y1 + gradient * (xend-x1); xgap=1 - fpart(x1 + .5) xpx11=xend; ypx11=floor(yend) intery=yend+gradient call plotXY xpx11, ypx11, brite(1 - fpart(yend*xgap)), switchXY call plotXY xpx11, ypx11+1, brite( fpart(yend*xgap)), switchXY xend=round(x2) /*◄─────────────────2nd endpoint.══════════════*/ yend=y2 + gradient * (xend-x2); xgap= fpart(x2 + .5) xpx12=xend; ypx12=floor(yend) call plotXY xpx12, ypx12 , brite(1 - fpart(yend*xgap)), switchXY call plotXY xpx12, ypx12+1, brite( fpart(yend*xgap)), switchXY
do x=xpx11+1 to xpx12-1 /*◄───draw the line.═════════════*/ !intery=floor(intery) call plotXY x, !intery , brite(1 - fpart(intery)), switchXY call plotXY x, !intery+1, brite( fpart(intery)), switchXY intery=intery + gradient end /*x*/ return
/*──────────────────────────────────────────────────────────────────────────────────────*/ brite: return substr(background || plotC, 1 + round( abs( arg(1) ) * length(plotC)), 1) floor: parse arg ?; _=trunc(?); return _ - (?<0) * (?\=_) fpart: parse arg ?; return abs(? - trunc(?)) round: return format(arg(1), , word(arg(2) 0, 1) ) /*──────────────────────────────────────────────────────────────────────────────────────*/ plotXY: parse arg xx,yy,bc,switchYX; if switchYX then parse arg yy,xx
image.xx.yy=bc; minX=min(minX, xx); maxX=max(maxX,xx) minY=min(minY, yy); maxY=max(maxY,yy); return</lang>
- output when using the default inputs:
····│··············· ····│··············· ····│··············· ····│··········█···· ····│·········█····· ····│········█······ ····│·······█······· ····│······█········ ····│·····█········· ····│····█·········· ····│···█··········· ····│··█············ ····│·█············· ····│█·············· ····│··············· ────┼─────────────── ····│··············· ····│···············
Ruby
<lang ruby>def ipart(n); n.truncate; end def fpart(n); n - ipart(n); end def rfpart(n); 1.0 - fpart(n); end
class Pixmap
def draw_line_antialised(p1, p2, colour) x1, y1 = p1.x, p1.y x2, y2 = p2.x, p2.y steep = (y2 - y1).abs > (x2 - x1).abs if steep x1, y1 = y1, x1 x2, y2 = y2, x2 end if x1 > x2 x1, x2 = x2, x1 y1, y2 = y2, y1 end deltax = x2 - x1 deltay = (y2 - y1).abs gradient = 1.0 * deltay / deltax # handle the first endpoint xend = x1.round yend = y1 + gradient * (xend - x1) xgap = rfpart(x1 + 0.5) xpxl1 = xend ypxl1 = ipart(yend) put_colour(xpxl1, ypxl1, colour, steep, rfpart(yend)*xgap) put_colour(xpxl1, ypxl1 + 1, colour, steep, fpart(yend)*xgap) itery = yend + gradient # handle the second endpoint xend = x2.round yend = y2 + gradient * (xend - x2) xgap = rfpart(x2 + 0.5) xpxl2 = xend ypxl2 = ipart(yend) put_colour(xpxl2, ypxl2, colour, steep, rfpart(yend)*xgap) put_colour(xpxl2, ypxl2 + 1, colour, steep, fpart(yend)*xgap) # in between (xpxl1 + 1).upto(xpxl2 - 1).each do |x| put_colour(x, ipart(itery), colour, steep, rfpart(itery)) put_colour(x, ipart(itery) + 1, colour, steep, fpart(itery)) itery = itery + gradient end end
def put_colour(x, y, colour, steep, c) x, y = y, x if steep self[x, y] = anti_alias(colour, self[x, y], c) end
def anti_alias(new, old, ratio) blended = new.values.zip(old.values).map {|n, o| (n*ratio + o*(1.0 - ratio)).round} RGBColour.new(*blended) end
end
bitmap = Pixmap.new(500, 500) bitmap.fill(RGBColour::BLUE) 10.step(430, 60) do |a|
bitmap.draw_line_antialised(Pixel[10, 10], Pixel[490,a], RGBColour::YELLOW) bitmap.draw_line_antialised(Pixel[10, 10], Pixel[a,490], RGBColour::YELLOW)
end bitmap.draw_line_antialised(Pixel[10, 10], Pixel[490,490], RGBColour::YELLOW)</lang>
Scala
Uses Bitmap#Scala. <lang Scala>import java.awt.Color import math.{floor => ipart, round, abs}
case class Point(x: Double, y: Double) {def swap = Point(y, x)}
def plotter(bm: RgbBitmap, c: Color)(x: Double, y: Double, v: Double) = {
val X = round(x).toInt val Y = round(y).toInt val V = v.toFloat // tint the existing pixels val c1 = c.getRGBColorComponents(null) val c2 = bm.getPixel(X, Y).getRGBColorComponents(null) val c3 = (c1 zip c2).map{case (n, o) => n * V + o * (1 - V)} bm.setPixel(X, Y, new Color(c3(0), c3(1), c3(2)))
}
def drawLine(plotter: (Double,Double,Double) => _)(p1: Point, p2: Point) {
def fpart(x: Double) = x - ipart(x) def rfpart(x: Double) = 1 - fpart(x) def avg(a: Float, b: Float) = (a + b) / 2
val steep = abs(p2.y - p1.y) > abs(p2.x - p1.x) val (p3, p4) = if (steep) (p1.swap, p2.swap) else (p1, p2) val (a, b) = if (p3.x > p4.x) (p4, p3) else (p3, p4) val dx = b.x - a.x val dy = b.y - a.y val gradient = dy / dx var intery = 0.0
def endpoint(xpxl: Double, yend: Double, xgap: Double) { val ypxl = ipart(yend) if (steep) { plotter(ypxl, xpxl, rfpart(yend) * xgap) plotter(ypxl+1, xpxl, fpart(yend) * xgap) } else { plotter(xpxl, ypxl , rfpart(yend) * xgap) plotter(xpxl, ypxl+1, fpart(yend) * xgap) } }
// handle first endpoint var xpxl1 = round(a.x); { val yend = a.y + gradient * (xpxl1 - a.x) val xgap = rfpart(a.x + 0.5) endpoint(xpxl1, yend, xgap) intery = yend + gradient }
// handle second endpoint val xpxl2 = round(b.x); { val yend = b.y + gradient * (xpxl2 - b.x) val xgap = fpart(b.x + 0.5) endpoint(xpxl2, yend, xgap) }
// main loop for (x <- (xpxl1 + 1) to (xpxl2 - 1)) { if (steep) { plotter(ipart(intery) , x, rfpart(intery)) plotter(ipart(intery)+1, x, fpart(intery)) } else { plotter(x, ipart (intery), rfpart(intery)) plotter(x, ipart (intery)+1, fpart(intery)) } intery = intery + gradient }
}</lang> Example:
Test line drawing in various directions including vertical, horizontal, 45° and oblique (such lines are drawn multiple times to test swapped parameters). <lang Scala>val r = 120 val img = new RgbBitmap(r*2+1, r*2+1) val line = drawLine(plotter(img, Color.GRAY)_)_ img.fill(Color.WHITE) for (angle <- 0 to 360 by 30; θ = math toRadians angle; θ2 = θ + math.Pi) {
val a = Point(r + r * math.sin(θ), r + r * math.cos(θ)) val b = Point(r + r * math.sin(θ2), r + r * math.cos(θ2)) line(a, b)
} javax.imageio.ImageIO.write(img.image, "png", new java.io.File("XiaolinWuLineAlgorithm.png"))</lang>
- Output:
View the PNG, available at the following URL because RosettaCode image uploads were disabled: https://lh5.googleusercontent.com/GxBAHV4nebuO1uiKboKc6nQmmtlJV47jPwVZnQHcbV7TKm0kjdKfKteclCfxmSdFJnSKvYYoB5I
Sidef
<lang ruby>func plot(x, y, c) {
c && printf("plot %d %d %.1f\n", x, y, c);
}
func fpart(x) {
x - int(x);
}
func rfpart(x) {
1 - fpart(x);
}
func drawLine(x0, y0, x1, y1) {
var p = plot; if (abs(y1 - y0) > abs(x1 - x0)) { p = {|arg| plot(arg[1, 0, 2]) }; (x0, y0, x1, y1) = (y0, x0, y1, x1); }
if (x0 > x1) { (x0, x1, y0, y1) = (x1, x0, y1, y0); }
var dx = (x1 - x0); var dy = (y1 - y0); var gradient = (dy / dx);
var xends = []; var intery;
# handle the endpoints for x,y in [[x0, y0], [x1, y1]] { var xend = int(x + 0.5); var yend = (y + gradient*(xend-x)); var xgap = rfpart(x + 0.5);
var x_pixel = xend; var y_pixel = yend.int; xends << x_pixel;
p.call(x_pixel, y_pixel , rfpart(yend) * xgap); p.call(x_pixel, y_pixel+1, fpart(yend) * xgap); defined(intery) && next;
# first y-intersection for the main loop intery = (yend + gradient); }
# main loop range(xends[0]+1, xends[1]-1).each { |x| p.call(x, intery.int, rfpart(intery)); p.call(x, intery.int+1, fpart(intery)); intery += gradient; }
}
drawLine(0, 1, 10, 2);</lang>
- Output:
plot 0 1 0.5 plot 10 2 0.5 plot 1 1 0.9 plot 1 2 0.1 plot 2 1 0.8 plot 2 2 0.2 plot 3 1 0.7 plot 3 2 0.3 plot 4 1 0.6 plot 4 2 0.4 plot 5 1 0.5 plot 5 2 0.5 plot 6 1 0.4 plot 6 2 0.6 plot 7 1 0.3 plot 7 2 0.7 plot 8 1 0.2 plot 8 2 0.8 plot 9 1 0.1 plot 9 2 0.9
Swift
<lang swift>import Darwin // apply pixel of color at x,y with an OVER blend to the bitmap public func pixel(color: Color, x: Int, y: Int) {
let idx = x + y * self.width if idx >= 0 && idx < self.bitmap.count { self.bitmap[idx] = self.blendColors(bot: self.bitmap[idx], top: color) }
}
// return the fractional part of a Double func fpart(_ x: Double) -> Double {
return modf(x).1
}
// reciprocal of the fractional part of a Double func rfpart(_ x: Double) -> Double {
return 1 - fpart(x)
}
// draw a 1px wide line using Xiolin Wu's antialiased line algorithm public func smoothLine(_ p0: Point, _ p1: Point) {
var x0 = p0.x, x1 = p1.x, y0 = p0.y, y1 = p1.y //swapable ptrs let steep = abs(y1 - y0) > abs(x1 - x0) if steep { swap(&x0, &y0) swap(&x1, &y1) } if x0 > x1 { swap(&x0, &x1) swap(&y0, &y1) } let dX = x1 - x0 let dY = y1 - y0 var gradient: Double if dX == 0.0 { gradient = 1.0 } else { gradient = dY / dX } // handle endpoint 1 var xend = round(x0) var yend = y0 + gradient * (xend - x0) var xgap = self.rfpart(x0 + 0.5) let xpxl1 = Int(xend) let ypxl1 = Int(yend) // first y-intersection for the main loop var intery = yend + gradient if steep { self.pixel(color: self.strokeColor.colorWithAlpha(self.rfpart(yend) * xgap), x: ypxl1, y: xpxl1) self.pixel(color: self.strokeColor.colorWithAlpha(self.fpart(yend) * xgap), x: ypxl1 + 1, y: xpxl1) } else { self.pixel(color: self.strokeColor.colorWithAlpha(self.rfpart(yend) * xgap), x: xpxl1, y: ypxl1) self.pixel(color: self.strokeColor.colorWithAlpha(self.fpart(yend) * xgap), x: xpxl1, y: ypxl1 + 1) } xend = round(x1) yend = y1 + gradient * (xend - x1) xgap = self.fpart(x1 + 0.5) let xpxl2 = Int(xend) let ypxl2 = Int(yend) // handle second endpoint if steep { self.pixel(color: self.strokeColor.colorWithAlpha(self.rfpart(yend) * xgap), x: ypxl2, y: xpxl2) self.pixel(color: self.strokeColor.colorWithAlpha(self.fpart(yend) * xgap), x: ypxl2 + 1, y: xpxl2) } else { self.pixel(color: self.strokeColor.colorWithAlpha(self.rfpart(yend) * xgap), x: xpxl2, y: ypxl2) self.pixel(color: self.strokeColor.colorWithAlpha(self.fpart(yend) * xgap), x: xpxl2, y: ypxl2 + 1) } // main loop if steep { for x in xpxl1+1..<xpxl2 { self.pixel(color: self.strokeColor.colorWithAlpha(self.rfpart(intery)), x: Int(intery), y: x) self.pixel(color: self.strokeColor.colorWithAlpha(self.fpart(intery)), x: Int(intery) + 1, y:x) intery += gradient } } else { for x in xpxl1+1..<xpxl2 { self.pixel(color: self.strokeColor.colorWithAlpha(self.rfpart(intery)), x: x, y: Int(intery)) self.pixel(color: self.strokeColor.colorWithAlpha(self.fpart(intery)), x: x, y: Int(intery) + 1) intery += gradient } }
} </lang>
Tcl
Uses code from Basic bitmap storage#Tcl <lang tcl>package require Tcl 8.5 package require Tk
proc ::tcl::mathfunc::ipart x {expr {int($x)}} proc ::tcl::mathfunc::fpart x {expr {$x - int($x)}} proc ::tcl::mathfunc::rfpart x {expr {1.0 - fpart($x)}}
proc drawAntialiasedLine {image colour p1 p2} {
lassign $p1 x1 y1 lassign $p2 x2 y2
set steep [expr {abs($y2 - $y1) > abs($x2 - $x1)}] if {$steep} { lassign [list $x1 $y1] y1 x1 lassign [list $x2 $y2] y2 x2 } if {$x1 > $x2} { lassign [list $x1 $x2] x2 x1 lassign [list $y1 $y2] y2 y1 } set deltax [expr {$x2 - $x1}] set deltay [expr {abs($y2 - $y1)}] set gradient [expr {1.0 * $deltay / $deltax}] # handle the first endpoint set xend [expr {round($x1)}] set yend [expr {$y1 + $gradient * ($xend - $x1)}] set xgap [expr {rfpart($x1 + 0.5)}] set xpxl1 $xend set ypxl1 [expr {ipart($yend)}] plot $image $colour $steep $xpxl1 $ypxl1 [expr {rfpart($yend)*$xgap}] plot $image $colour $steep $xpxl1 [expr {$ypxl1+1}] [expr {fpart($yend)*$xgap}] set itery [expr {$yend + $gradient}]
# handle the second endpoint set xend [expr {round($x2)}] set yend [expr {$y2 + $gradient * ($xend - $x2)}] set xgap [expr {rfpart($x2 + 0.5)}] set xpxl2 $xend set ypxl2 [expr {ipart($yend)}] plot $image $colour $steep $xpxl2 $ypxl2 [expr {rfpart($yend)*$xgap}] plot $image $colour $steep $xpxl2 [expr {$ypxl2+1}] [expr {fpart($yend)*$xgap}]
for {set x [expr {$xpxl1 + 1}]} {$x < $xpxl2} {incr x} { plot $image $colour $steep $x [expr {ipart($itery)}] [expr {rfpart($itery)}] plot $image $colour $steep $x [expr {ipart($itery) + 1}] [expr {fpart($itery)}] set itery [expr {$itery + $gradient}] }
}
proc plot {image colour steep x y c} {
set point [expr {$steep ? [list $y $x] : [list $x $y]}] set newColour [antialias $colour [getPixel $image $point] $c] setPixel $image $newColour $point
}
proc antialias {newColour oldColour c} {
# get the new colour r,g,b if {[scan $newColour "#%2x%2x%2x%c" nr ng gb -] != 3} { scan [colour2rgb $newColour] "#%2x%2x%2x" nr ng nb }
# get the current colour r,g,b scan $oldColour "#%2x%2x%2x" cr cg cb # blend the colours in the ratio defined by "c" foreach new [list $nr $ng $nb] curr [list $cr $cg $cb] { append blend [format {%02x} [expr {round($new*$c + $curr*(1.0-$c))}]] } return #$blend
}
proc colour2rgb {color_name} {
foreach part [winfo rgb . $color_name] { append colour [format %02x [expr {$part >> 8}]] } return #$colour
}
set img [newImage 500 500] fill $img blue for {set a 10} {$a < 500} {incr a 60} {
drawAntialiasedLine $img yellow {10 10} [list 490 $a] drawAntialiasedLine $img yellow {10 10} [list $a 490]
} toplevel .wu label .wu.l -image $img pack .wu.l</lang>