Greyscale bars/Display: Difference between revisions
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[https://github.com/ljr1981/rosettacode_answers/blob/main/testing/rc_greyscale_bars/eifgreyscale.png PNG Output] |
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<lang> |
<lang eiffel> |
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feature -- Test routines |
feature -- Test routines |
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Revision as of 12:27, 16 August 2022
You are encouraged to solve this task according to the task description, using any language you may know.
The task is to display a series of vertical greyscale bars (contrast bars) with a sufficient number of bars to span the entire width of the display.
For the top quarter of the display, the left hand bar should be black, and we then incrementally step through six shades of grey until we have a white bar on the right hand side of the display. (This gives a total of 8 bars)
For the second quarter down, we start with white and step down through 14 shades of gray, getting darker until we have black on the right hand side of the display. (This gives a total of 16 bars).
Halfway down the display, we start with black, and produce 32 bars, ending in white, and for the last quarter, we start with white and step through 62 shades of grey, before finally arriving at black in the bottom right hand corner, producing a total of 64 bars for the bottom quarter.
ActionScript
<lang ActionScript>package { import flash.display.Sprite;
[SWF(width="640", height="480")] public class GreyscaleBars extends Sprite {
public function GreyscaleBars() { _drawRow(8, 0); _drawRow(16, stage.stageHeight/4, true); _drawRow(32, stage.stageHeight/2); _drawRow(64, stage.stageHeight/4 * 3, true); }
private function _drawRow(nbSteps : uint, startingY : uint, reverse : Boolean = false) : void {
for (var i : int = 0; i < nbSteps; i++) { graphics.beginFill(0x00, reverse ? 1 - (i/nbSteps) : (i/nbSteps)); graphics.drawRect(i * stage.stageWidth / nbSteps, startingY, stage.stageWidth/nbSteps, stage.stageHeight/4); graphics.endFill(); } } } }</lang>
Ada
<lang Ada>with Gtk.Window; use Gtk.Window; with Gtk.Enums; with Gtk.Handlers; with Gtk.Main; with Gdk; with Gdk.Event; with Glib; use Glib; with Cairo; use Cairo; with Gdk.Cairo; pragma Elaborate_All (Gtk.Handlers);
procedure Greyscale is
Win : Gtk_Window; Width : constant := 640; Height : constant := 512;
package Handlers is new Gtk.Handlers.Callback (Gtk_Window_Record);
package Event_Cb is new Gtk.Handlers.Return_Callback (
Widget_Type => Gtk_Window_Record,
Return_Type => Boolean);
procedure Quit (Win : access Gtk_Window_Record'Class) is
pragma Warnings (Off, Win);
begin
Gtk.Main.Main_Quit;
end Quit;
function Expose
(Drawing : access Gtk_Window_Record'Class;
Event : Gdk.Event.Gdk_Event)
return Boolean
is
subtype Dub is Glib.Gdouble;
Cr : Cairo_Context;
Revert : Boolean;
Grey : Dub;
DH : constant Dub := Dub (Height) / 4.0;
X, Y, DW : Dub;
N : Natural;
begin
Cr := Gdk.Cairo.Create (Get_Window (Drawing));
for Row in 1 .. 4 loop
N := 2 ** (Row + 2);
Revert := (Row mod 2) = 0;
DW := Dub (Width) / Dub (N);
X := 0.0;
Y := DH * Dub (Row - 1);
for B in 0 .. (N - 1) loop
Grey := Dub (B) / Dub (N - 1);
if Revert then
Grey := 1.0 - Grey;
end if;
Cairo.Set_Source_Rgb (Cr, Grey, Grey, Grey);
Cairo.Rectangle (Cr, X, Y, DW, DH);
Cairo.Fill (Cr);
X := X + DW;
end loop;
end loop;
Cairo.Destroy (Cr);
return False;
end Expose;
begin
Gtk.Main.Set_Locale; Gtk.Main.Init;
Gtk_New (Win);
Gtk.Window.Initialize (Win, Gtk.Enums.Window_Toplevel);
Set_Title (Win, "Greyscale with GTKAda");
Set_Default_Size (Win, Width, Height);
Set_App_Paintable (Win, True);
-- Attach handlers
Handlers.Connect (Win, "destroy", Handlers.To_Marshaller (Quit'Access));
Event_Cb.Connect
(Win,
"expose_event",
Event_Cb.To_Marshaller (Expose'Access));
Show_All (Win);
Gtk.Main.Main;
end Greyscale; </lang>
Amazing Hopper
Version: hopper-FLOW! <lang Amazing Hopper>
- include <flow.h>
- include <flow-term.h>
- define SPACE(_T_,_N_) REPLICATE( " ", {_T_}DIV-INTO(_N_) )
DEF-MAIN(argv,argc)
CLR-SCR GOSUB( Print Grey Scale )
END
RUTINES
DEF-FUN( Print Grey Scale )
SET( nrcolors, 8 )
SET( direction, 1 )
MSET( quarter, color )
LOCATE( 0, 0 )
FOR( LT?( quarter, 4 ), ++quarter )
SET( height, 0 )
FOR( LT?( height, 5 ), ++height )
SET( width, 0 )
FOR( LT?( width, nrcolors ), ++width )
LET( color := CEIL( MUL( width, DIV( 255, SUB(nrcolors,1) ) ) ) )
WHEN( NOT( MOD( direction, 2 ) ) ){
LET( color := SUB( 255, color ) )
}
PRN( COLOR-RGBB( color, color, color) SPACE( 128, nrcolors ) )
NEXT
PRNL("\OFF")
NEXT
nrcolors*=2
++direction
NEXT
RET </lang>
ANSI Standard BASIC
<lang ANSI Standard BASIC>100 SET WINDOW 0,1279,0,1023 110 REM (0,0) is the bottom left of the display 120 SET AREA COLOR 1 ! Select color one for drawing 130 FOR row=1 TO 4 140 LET n=IP(2^(row+2)) 150 LET w=IP(1280/n) 160 LET py=IP(256*(4-row)) 170 FOR b=0 TO n-1 180 LET g=b/(n-1) 190 IF n=16 OR n=64 THEN LET g=1-g 200 SET COLOR MIX(1) g,g,g ! Reprogram color 1 to the gray we want 210 PLOT AREA: w*b,py; w*b+w,py; w*b+w,py+256; w*b,py+256 220 NEXT b 230 NEXT row 240 END</lang>
AutoHotkey
Requires the GDI+ Standard Library by tic: http://www.autohotkey.com/forum/viewtopic.php?t=32238 <lang AHK>h := A_ScreenHeight w := A_ScreenWidth pToken := gdip_Startup() hdc := CreateCompatibleDC() hbm := CreateDIBSection(w, h) obm := SelectObject(hdc, hbm) G := Gdip_GraphicsFromHDC(hdc)
OnExit, Exit
Gui +E0x80000 +LastFound +OwnDialogs +Owner +AlwaysOnTop hwnd := WinExist() Gui Show, NA
columnHeight := h/4
Loop 4 { columnY := (A_Index-1) * columnHeight columnCount := 2**(A_Index+2) colorgap := 255 / (columnCount-1) columnWidth := w/ColumnCount If (A_Index & 1) colorComp := 0 else colorComp := 255 ,colorgap *= -1 MsgBox % colorGap * columnCount Loop % columnCount { columnX := (A_Index-1) * columnWidth pBrush := Gdip_BrushCreateSolid(QColor(colorComp, colorComp, colorComp)) Gdip_FillRectangle(G, pBrush, columnX, columnY, columnWidth, columnHeight) Gdip_DeleteBrush(pBrush) colorComp += colorgap } SetFormat, IntegerFast, hex SetFormat, IntegerFast, D }
UpdateLayeredWindow(hwnd, hdc, 0, 0, W, H)
SelectObject(hdc, obm) DeleteObject(hbm) DeleteDC(hdc) Gdip_DeleteGraphics(G) Return
Esc:: Exit: Gdip_Shutdown(pToken) ExitApp
QColor(r, g, b){ return 0xFF000000 | (r << 16) | (g << 8) | (b) }</lang>
AWK
<lang awk> BEGIN {
nrcolors = 8 direction = 1
for (quarter=0; quarter<4; quarter++) {
for (height=0; height<5; height++) {
for (width=0; width<nrcolors; width++) {
# gradient goes white-to-black or black-to-white depending on direction
if (direction % 2)
color = width * (255 / (nrcolors-1))
else
color = 255 - width * (255 / (nrcolors-1))
# print (ANSI) RGB greysacle color and amount of spaces
printf("\033[48;2;%d;%d;%dm%*s", color, color, color, 64 / nrcolors, " ")
}
# reset color and print newline
printf("\033[0m\n")
}
# 8, 16, 32, 64 colors and alternating direction of gradient nrcolors *= 2 direction++ }
} </lang>
BASIC256
<lang> h=ceil(graphheight/4) for row=1 to 4
w=ceil(graphwidth/(8*row))
c=255/(8*row-1)
for n = 0 to (8*row-1)
color 255-c*n,255-c*n,255-c*n
if row/2 = int(row/2) then color c*n,c*n,c*n
rect n*w,h*(row-1),w,h
next n
next row </lang>
BBC BASIC
<lang bbcbasic>MODE 8:REM 640 x 512 pixel display mode: BBC BASIC gives 2 graphics points per pixel REM (0,0) is the bottom left of the display GCOL 1 :REM Select colour one for drawing FOR row%=1 TO 4
n%=2^(row%+2) w%=1280/n% py%=256*(4-row%) FOR b%=0 TO n%-1 g%=255*b%/(n%-1) IF n%=16 OR n%=64 THEN g%=255-g% COLOUR 1,g%,g%,g% : REM Reprogram colour 1 to the grey we want RECTANGLE FILL w%*b%,py%,w%,256 NEXT b%
NEXT row%</lang>
C
<lang c>#include <gtk/gtk.h> /* do some greyscale plotting */ void gsplot (cairo_t *cr,int x,int y,double s) {
cairo_set_source_rgb (cr,s,s,s); cairo_move_to (cr,x+0.5,y); cairo_rel_line_to (cr,0,1); cairo_stroke (cr);
} /* make a shaded widget */ gboolean expose_event (GtkWidget *widget,GdkEventExpose *event,gpointer data) {
int r,c,x=0;
cairo_t *cr;
cr = gdk_cairo_create (widget->window);
cairo_scale (cr,5,50);
cairo_set_line_width (cr,1);
for (r=0;r<4;r++) {
c = (r&1)*64-(r%2);
do gsplot (cr,x++%64,r,c/(1<<(3-r))/(8*(1<<r)-1.0));
while ((c+=2*!(r%2)-1)!=(!(r%2))*64-(r%2));
} cairo_destroy (cr);
return FALSE;
} /* main */ int main (int argc, char *argv[]) {
GtkWidget *window; gtk_init (&argc, &argv); window = gtk_window_new (GTK_WINDOW_TOPLEVEL); g_signal_connect (window, "expose-event",G_CALLBACK (expose_event), NULL); g_signal_connect (window, "delete-event", G_CALLBACK(gtk_main_quit), NULL); gtk_window_set_default_size (GTK_WINDOW(window), 320, 200); gtk_widget_set_app_paintable (window, TRUE); gtk_widget_show_all (window); gtk_main (); return 0;
} </lang>
C#
<lang csharp>using System; using System.Drawing; using System.Windows.Forms; static class Program { static void Main() { Application.Run(new FullScreen()); } } public sealed class FullScreen : Form {
const int ColorCount = 256;
public FullScreen()
{
FormBorderStyle = FormBorderStyle.None;
WindowState = FormWindowState.Maximized;
KeyPress += (s, e) => Application.Exit();
BackgroundImage = ColorBars(Screen.FromControl(this).Bounds);
}
private static Bitmap ColorBars(Rectangle size)
{
var colorBars = new Bitmap(size.Width, size.Height);
Func<int, int, int> forwardColor = (x, divs) => (int)(x * ((float)divs / size.Width)) * ColorCount / divs;
Func<int, int, int> reverseColor = (x, divs) => ColorCount - 1 - forwardColor(x, divs);
Action<int, int, int> setGray = (x, y, gray) => colorBars.SetPixel(x, y, Color.FromArgb(gray, gray, gray));
Action<int, int, int> setForward = (x, y, divs) => setGray(x, y, forwardColor(x, divs));
Action<int, int, int> setReverse = (x, y, divs) => setGray(x, y, reverseColor(x, divs));
int verticalStripe = size.Height / 4;
for (int x = 0; x < size.Width; x++)
{
for (int y = 0; y < verticalStripe; y++) setForward(x, y, 8);
for (int y = verticalStripe; y < verticalStripe * 2; y++) setReverse(x, y, 16);
for (int y = verticalStripe * 2; y < verticalStripe * 3; y++) setForward(x, y, 32);
for (int y = verticalStripe * 3; y < verticalStripe * 4; y++) setReverse(x, y, 64);
}
return colorBars;
}
}</lang>
C++
using Qt 4.6
file greytones.h
<lang cpp>#ifndef MYWIDGET_H
- define MYWIDGET_H
- include <QWidget>
class QPaintEvent ;
class MyWidget : public QWidget { public :
MyWidget( ) ;
protected :
void paintEvent( QPaintEvent * ) ;
} ;
- endif</lang>
file greytones.cpp
<lang cpp>#include <QtGui>
- include "greytones.h"
MyWidget::MyWidget( ) {
setGeometry( 0, 0 , 640 , 480 ) ;
}
void MyWidget::paintEvent ( QPaintEvent * ) {
QBrush myBrush( Qt::SolidPattern ) ;
QPainter myPaint( this ) ;
int run = 0 ; //how often have we run through the loop ?
int colorcomp = 0 ;
for ( int columncount = 8 ; columncount < 128 ; columncount *= 2 ) {
int colorgap = 255 / columncount ;
int columnwidth = 640 / columncount ; // 640 being the window width
int columnheight = 480 / 4 ; //we're looking at quarters
if ( run % 2 == 0 ) { //we start with black columns
colorcomp = 0 ;
}
else { //we start with white columns
colorcomp = 255 ; colorgap *= -1 ; //we keep subtracting color values
}
int ystart = 0 + columnheight * run ; //determines the y coordinate of the first column per row
int xstart = 0 ;
for ( int i = 0 ; i < columncount ; i++ ) {
myBrush.setColor( QColor( colorcomp, colorcomp , colorcomp ) ) ; myPaint.fillRect( xstart , ystart , columnwidth , columnheight , myBrush ) ; xstart += columnwidth ; colorcomp += colorgap ; //we choose the next color
}
run++ ;
}
}</lang>
file main.cpp
<lang cpp>#include <QApplication>
- include "greytones.h"
int main( int argc, char * argv[ ] ) {
QApplication app( argc , argv ) ; MyWidget window ; window.setWindowTitle( QApplication::translate( "greyScales" , "grey scales demonstration" ) ) ; window.show( ) ; return app.exec( ) ;
}</lang>
Component Pascal
<lang oberon2> MODULE RosettaGreys; IMPORT Views, Ports, Properties, Controllers, StdLog;
CONST (* orient values *) left = 1; right = 0;
TYPE View = POINTER TO RECORD (Views.View) END;
PROCEDURE LoadGreyPalette(VAR colors: ARRAY OF Ports.Color); VAR i, step, hue: INTEGER; BEGIN step := 255 DIV LEN(colors); FOR i := 1 TO LEN(colors) DO hue := i * step; colors[i - 1] := Ports.RGBColor(hue,hue,hue) END END LoadGreyPalette;
PROCEDURE (v: View) Restore(f: Views.Frame; l, t, r, b: INTEGER); VAR i, w, h: INTEGER; colors: POINTER TO ARRAY OF Ports.Color;
PROCEDURE Draw(row, cols: INTEGER; orient: INTEGER); VAR w: INTEGER; c: Ports.Color; BEGIN NEW(colors,cols);LoadGreyPalette(colors^); w := (r - l) DIV cols; FOR i := 1 TO cols DO IF orient = left THEN c := colors[cols - i] ELSE c := colors[i - 1] END; f.DrawRect((l + w) * (i - 1), t + (row - 1) * h, (l + w) * i, t + row * h,Ports.fill,c); END END Draw; BEGIN h := (b - t) DIV 4; Draw(1,8,right); Draw(2,16,left); Draw(3,32,right); Draw(4,64,left); END Restore;
PROCEDURE (v: View) HandlePropMsg(VAR msg: Properties.Message); CONST min = 5 * Ports.mm; max = 50 * Ports.mm; VAR stdProp: Properties.StdProp; prop: Properties.Property; BEGIN WITH msg: Properties.SizePref DO IF (msg.w = Views.undefined) OR (msg.h = Views.undefined) THEN msg.w := 100 * Ports.mm; msg.h := 35 * Ports.mm END ELSE (* ignore other messages *) END END HandlePropMsg;
PROCEDURE Deposit*; VAR v: View; BEGIN NEW(v); Views.Deposit(v) END Deposit; END RosettaGreys.
"RosettaGreys.Deposit; StdCmds.Open"
</lang>
EasyLang
<lang>n = 8 for row range 4
sz = 100 / n
for i range n
c = i / (n - 1)
if row mod 2 = 1
c = 1 - c
.
color3 c c c
move sz * i row * 25
rect sz + 1 25
.
n *= 2
.</lang>
Eiffel
<lang eiffel> feature -- Test routines
rc_greyscale_bars_test -- Greyscale bars/Display note testing: "execution/isolated", "execution/serial" local y: INTEGER do y := 0 paint_row (black, y, r1_div_count, r1_width)
y := y + row_height paint_row (white, y, r2_div_count, r2_width)
y := y + row_height paint_row (black, y, r3_div_count, r3_width)
y := y + row_height paint_row (white, y, r4_div_count, r4_width)
pic.save_to_named_file (create {EV_PNG_FORMAT}, ".\testing\rc_greyscale_bars\eifgreyscale.png") end
feature {NONE} -- Test Support
paint_row (a_init_color: REAL; a_y, r_div, r_width: INTEGER) -- `paint_row' with rectangles from `black' to `white' or reverse. require valid_color: a_init_color = white or else a_init_color = black valid_y: (<<0,row_height * 1, row_height * 2, row_height * 3>>).has (a_y) valid_div: (<<r1_div_count, r2_div_count, r3_div_count, r4_div_count>>).has (r_div) valid_width: (<<r1_width, r2_width, r3_width, r4_width>>).has (r_width) local color: REAL x, dir: INTEGER do color := a_init_color if color = white then dir := down else dir := up end ⟳ i:1 |..| r_div ¦ pic.set_foreground_color (create {EV_COLOR}.make_with_rgb (color, color, color)) pic.fill_rectangle (x, a_y, r_width, row_height) color := color + ((1/r_div).truncated_to_real * dir) x := x + r_width ⟲ end
feature -- Constants
pic: EV_PIXMAP once create Result.make_with_size (width, height) end
width: INTEGER = 1024 height: INTEGER = 768
row_height: INTEGER once Result := (height / 4).truncated_to_integer end
r1_width: INTEGER = 128; r1_div_count: INTEGER = 8 r2_width: INTEGER = 64; r2_div_count: INTEGER = 16 r3_width: INTEGER = 32; r3_div_count: INTEGER = 32 r4_width: INTEGER = 16; r4_div_count: INTEGER = 64
black: REAL = 0.0 white: REAL = 1.0 down: INTEGER = -1 up: INTEGER = 1 </lang>
Euler Math Toolbox
<lang Euler Math Toolbox> >function grayscale(y1,y2,n,direction=1) ... $ loop 0 to n-1; $ s=#/(n-1); barcolor(rgb(s,s,s)); $ if direction==1 then plotbar(#/n,y1,1/n,y2-y1); $ else plotbar(1-(#+1)/n,y1,1/n,y2-y1); $ endif; $ end; $endfunction >function grayscales () ... $ aspect(2); barstyle("#"); $ window(0,0,1023,1023); margin(0); setplot(0,1,0,1); $ clg; $ hold on; $ grayscale(3/4,1,8,1); $ grayscale(1/2,3/4,14,-1); $ grayscale(1/4,1/2,32,1); $ grayscale(0,1/4,64,-1); $ hold off; $endfunction >grayscales: </lang>
FreeBASIC
<lang freebasic>' version 01-09-2017 ' compile with: fbc -s console ' or compile with: fbc -s gui ' hit any key to stop
Dim As UInteger d, blocks, blocksize, ps, col, h, w, x, y1, y2
ScreenInfo w, h ' create display size window, 8bit color (palette), no frame ScreenRes w, h, 8,, 8
For x = 0 To 255 ' create grayscale palette for
Palette x, x, x, x ' the window we just opened
Next
h = h \ 4 : y2 = h -1
If w Mod 64 <> 0 Then w -= (w Mod 64) blocks = 8 : blocksize = w \ 8
For ps = 1 To 4
For x = 0 To blocks -1
col = 255 * x \ (blocks -1) ' from black to white
If (ps And 1) = 0 Then col = 255 - col ' from white to black
Line (x * blocksize, y1) - (((x +1) * blocksize) -1, y2), col, bf
Next
y1 += h : y2 += h
blocks *= 2 : blocksize \= 2
Next
' empty keyboard buffer While Inkey <> "" : Wend
Sleep End</lang>
Frink
<lang frink> fakewidth =!= dummy
g = new graphics g.antialiased[false] drawBars[g, 0, 1, 0, 1/4, 8] drawBars[g, 1, 0, 1/4, 1/2, 16] drawBars[g, 0, 1, 1/2, 3/4, 32] drawBars[g, 1, 0, 3/4, 1, 64] g.show[640,480,1] // No portable fullscreen mode; user must maximize window.
drawBars[g is graphics, leftColor, rightColor, top, bottom, steps] := {
colorStep = (rightColor - leftColor) / steps
color = leftColor
for i=0 to steps-1
{
g.color[color, color, color]
g.fillRectSides[i/dummy/steps, top, (i+1)/dummy/steps, bottom]
color = color + colorStep
}
} </lang>
FutureBasic
<lang futurebasic> _window = 1
void local fn BuildGrayBarWindow
NSInteger i float gray CGRect r = fn CGRectMake( 0, 0, 640, 400 ) window _window, @"Gray Scale Window", r WindowSetBackgroundColor( _window, fn ColorBlack ) gray = 0.0 r = fn CGrectMake( 0, 300, 80, 100 ) for i = 1 to 8 textfield i, YES,,r,_window TextFieldSetEditable( i, NO ) TextFieldSetBackgroundColor( i, fn ColorWithRGB( gray, gray, gray, 1.0 ) ) r = fn CGRectOffset( r, 80, 0 ) gray += 0.142857142857143 // 1/7 next gray = 1.0 r = fn CGrectMake( 0, 200, 40, 100 ) for i = 11 to 26 textfield i, YES,,r,_window TextFieldSetEditable( i, NO ) TextFieldSetBackgroundColor( i, fn ColorWithRGB( gray, gray, gray, 1.0 ) ) r = fn CGRectOffset( r, 40, 0 ) gray -= 0.066666666666667 // 1/5 next gray = 0.0 r = fn CGrectMake( 0, 100, 20, 100 ) for i = 31 to 62 textfield i, YES,,r,_window TextFieldSetEditable( i, NO ) TextFieldSetBackgroundColor( i, fn ColorWithRGB( gray, gray, gray, 1.0 ) ) r = fn CGRectOffset( r, 20, 0 ) gray += 0.032258064516129 // 1/31 next gray = 1.0 r = fn CGrectMake( 0, 0, 10, 100 ) for i = 101 to 164 textfield i, YES,,r,_window TextFieldSetEditable( i, NO ) TextFieldSetBackgroundColor( i, fn ColorWithRGB( gray, gray, gray, 1.0 ) ) r = fn CGRectOffset( r, 10, 0 ) gray -= 0.015873015873016 // 1/63 next
end fn
fn BuildGrayBarWindow
HandleEvents </lang>
- Output:
[See accompanying screenshot.]
And here's another clever and shorter solution: <lang futurebasic>void local fn BuildWindow
CGRect r = {0,0,640,400}
long i, j, bars = 8
CGFloat gray, delta, y = 0.0, w = 80
window 1, @"Grayscale Bars", r
pen -1
for j = 1 to 4
delta = 1.0/(bars-1)
if ( j mod 2 ) then gray = 0.0 else gray = 1.0 : delta = -delta
r = fn CGRectMake( 0, y, w, 100 )
for i = 1 to bars
rect fill r, fn ColorWithWhite( gray, 1.0 )
r.origin.x += w
gray += delta
next
bars = bars << 1
y += 100 : w = w/2
next
end fn
fn BuildWindow
HandleEvents</lang>
Gambas
<lang gambas>Public Sub Form_Open() Dim iRow, iCol, iClr As Integer 'For Row, Column and Colour Dim iInc As Integer = 4 'To calculate RGB colour Dim h1Panel As Panel 'Panels to display colours
With Me 'Setup the Form
.Arrangement = Arrange.Row 'Arrange children in rows .Border = False 'No Border .Height = Desktop.Height 'Fill the screen .Width = Desktop.Width 'Fill the screen .Fullscreen = True 'Set the Form to Fullscreen
End With
For iRow = 1 To 4 'For each row..
iInc += iInc 'Increase iInc by itself
For iCol = 0 To iInc - 1 'For each column..
iClr = iCol * (256 / iInc) 'Set the RGB colour
If iRow = 2 Or iRow = 4 Then iClr = 255 - (iCol * (256 / iInc)) 'If row 2 or 4 then reverse the colours
h1Panel = New Panel(Me) 'Create a new Panel
With h1Panel 'With the Panel..
.Width = Desktop.Width / iInc 'Set the width
.Height = Desktop.Height / 4 'Set the height
.Background = Color.RGB(iClr, iClr, iClr) 'Set the Background colour
.Border = Border.Plain 'Set a Border (It's easier to see the colour changes)
End With
Next
Next
End</lang>
Click here for image of the output
Go
<lang go>package main
import (
"github.com/fogleman/gg" "math"
)
func greyBars(dc *gg.Context) {
run := 0
colorComp := 0.0 // component of the color
for colCount := 8; colCount < 128; colCount *= 2 {
// by this gap we change the background color
colorGap := 255.0 / float64(colCount-1)
colWidth := float64(dc.Width() / colCount)
colHeight := float64(dc.Height() / 4)
// switches color directions with each iteration of for loop
if run%2 == 0 {
colorComp = 0.0
} else {
colorComp = 255.0
colorGap = -colorGap
}
xstart, ystart := 0.0, colHeight*float64(run)
for i := 0; i < colCount; i++ {
icolor := int(math.Round(colorComp)) // round to nearer integer
dc.SetRGB255(icolor, icolor, icolor)
dc.DrawRectangle(xstart, ystart, colWidth, colHeight)
dc.Fill()
xstart += colWidth
colorComp += colorGap
}
run++
}
}
func main() {
dc := gg.NewContext(640, 320)
greyBars(dc)
dc.SavePNG("greybars.png")
}</lang>
- Output:
Image similar to R entry (first image)
Haskell
This program uses an inlined XPM file which is scaled to fill an entire GTK fullscreen window
<lang Haskell>import Graphics.UI.Gtk import Graphics.UI.Gtk.Gdk.GC import Control.Monad.Trans (liftIO)
-- click on the window to exit.
main = do
initGUI
window <- windowNew
buf <- pixbufNewFromXPMData bars
widgetAddEvents window [ButtonPressMask]
on window objectDestroy mainQuit
on window exposeEvent (paint buf)
on window buttonPressEvent $
liftIO $ do { widgetDestroy window; return True }
windowFullscreen window widgetShowAll window mainGUI
paint :: Pixbuf -> EventM EExpose Bool paint buf = do
pix <- eventWindow
liftIO $ do
(sx, sy) <- drawableGetSize pix
newBuf <- pixbufScaleSimple buf sx sy InterpNearest
gc <- gcNewWithValues pix newGCValues
drawPixbuf pix gc newBuf 0 0 0 0 (-1) (-1) RgbDitherNone 0 0
return True
bars :: [String] bars = [
"64 4 65 1 1 1"," c None","A c #000000",
"C c #080808","D c #0C0C0C","E c #101010","F c #141414",
"G c #181818","H c #1C1C1C","I c #202020","J c #242424",
"K c #282828","L c #2C2C2C","M c #303030","N c #343434",
"O c #383838","P c #3C3C3C","Q c #404040","R c #444444",
"S c #484848","T c #4C4C4C","U c #505050","V c #545454",
"W c #585858","X c #5C5C5C","Y c #606060","Z c #646464",
"a c #686868","b c #6C6C6C","c c #707070","d c #747474",
"e c #787878","f c #7C7C7C","g c #808080","h c #848484",
"i c #888888","j c #8C8C8C","k c #909090","l c #949494",
"m c #989898","n c #9C9C9C","o c #A0A0A0","p c #A4A4A4",
"q c #A8A8A8","r c #ACACAC","s c #B0B0B0","t c #B4B4B4",
"u c #B8B8B8","v c #BCBCBC","w c #C0C0C0","x c #C4C4C4",
"y c #C8C8C8","z c #CCCCCC","0 c #D0D0D0","1 c #D4D4D4",
"2 c #D8D8D8","3 c #DCDCDC","4 c #E0E0E0","5 c #E4E4E4",
"6 c #E8E8E8","7 c #ECECEC","8 c #F0F0F0","9 c #F4F4F4",
". c #F8F8F8","+ c #FCFCFC","* c #FFFFFF",
"AAAAAAAAJJJJJJJJRRRRRRRRZZZZZZZZhhhhhhhhppppppppxxxxxxxx********",
"****88881111xxxxttttppppllllhhhhddddZZZZVVVVRRRRNNNNJJJJFFFFAAAA",
"AADDFFHHJJLLNNPPRRTTVVXXZZbbddffhhjjllnnpprrttvvxxzz11336688..**",
"*+.9876543210zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCA"
]</lang>
Icon and Unicon
This procedure uses code from the Colour bars/Display task, specifically the: DrawTestCard procedure and testcard, band, and bar records which are used to build structures that can be easily transcribed into independent bands and bars.
<lang Icon>link graphics,printf,numbers
procedure main()
DrawTestCard(GreyScale_TestCard()) WDone()
end
procedure greyscale(l,h,s) #: generate s greys over range l:h every i := round(l to h+1 by ((h-l)/(s-1.))) do suspend sprintf("%d,%d,%d",i,i,i) # return rgb black-grey-white end
procedure GreyScale_TestCard() #: return greyscale testcard
TC := testcard(,"GreyScale Test Card",
width := 800, height := 600,
list(numbands := 4) )
maxv := 2^16-1 # largest colour value
every (iv := [], i := 1 to numbands) do { # for each band
every put(v := [], greyscale(0,maxv,2^(2+i))) # compute greyscale
put(iv, if i%2 = 0 then v else reverse(v)) # switch directions }
every r := height/numbands * ((i := 1 to numbands)-1) + 1 do {
TC.bands[i] := band(r,[])
every c := width/(*iv[i]) * ((j := 1 to *iv[i])-1) + 1 do
put(TC.bands[i].bars, bar( c, iv[i,j]))
put((TC.bands[i]).bars, bar(width)) # right sentinal
}
put(TC.bands,band(height)) # bottom sentinal
return TC
end</lang>
graphics.icn supports graphics printf.icn provides sprintf, etc. numbers.icn provides round
J
Solution: <lang j> load 'viewmat'
NB. size=. 2{.".wd'qm' NB. J6
NB. size=. getscreenwh_jgtk_ NB. J7
size=. 2 3{_".wd'qscreen' NB. J9
rows=. (2^3+i.4),._1^i.4
bars=. ((64%{.)#[:(<:@|%~i.)*/)"1 rows
togreyscale=. (256#. [:<.255 255 255&*)"0
'rgb' viewmat (4<.@%~{:size)# (64<.@%~{.size)#"1 togreyscale bars
wd 'pmove 0 _30 ',":size [ wd 'psel ',1{::,hforms_jviewmat_ NB. J9</lang>
Note that hardware changes over the years have left their mark on interface protocols, which shows up here as language changes.
Java
using basically the same code as in the C++ example <lang Java>import javax.swing.* ; import java.awt.* ;
public class Greybars extends JFrame {
private int width ; private int height ;
public Greybars( ) {
super( "grey bars example!" ) ;
width = 640 ;
height = 320 ;
setSize( width , height ) ;
setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE ) ;
setVisible( true ) ;
}
public void paint ( Graphics g ) {
int run = 0 ;
double colorcomp = 0.0 ; //component of the color
for ( int columncount = 8 ; columncount < 128 ; columncount *= 2 ) {
double colorgap = 255.0 / (columncount - 1) ; //by this gap we change the background color int columnwidth = width / columncount ; int columnheight = height / 4 ; if ( run % 2 == 0 ) //switches color directions with every for loop colorcomp = 0.0 ; else { colorcomp = 255.0 ; colorgap *= -1.0 ; } int ystart = 0 + columnheight * run ; int xstart = 0 ; for ( int i = 0 ; i < columncount ; i++ ) {
int icolor = (int)Math.round(colorcomp) ; //round to nearer integer
Color nextColor = new Color( icolor , icolor, icolor ) ; g.setColor( nextColor ) ; g.fillRect( xstart , ystart , columnwidth , columnheight ) ; xstart += columnwidth ; colorcomp += colorgap ; } run++ ;
} }
public static void main( String[ ] args ) {
Greybars gb = new Greybars( ) ;
}
}</lang>
JavaScript
Live Demo: http://jsfiddle.net/gcN9g/embedded/result/ <lang JavaScript><html><body> <script type="text/javascript"> var width = 640; var height = 400; var c = document.createElement("canvas"); c.setAttribute('id', 'myCanvas'); c.setAttribute('style', 'border:1px solid black;'); c.setAttribute('width', width); c.setAttribute('height', height); document.body.appendChild(c); var ctx = document.getElementById('myCanvas').getContext("2d");
var columnCount = 8; // number of columns var rowCount = 4; // number of rows var direction = 1; // 1 = from left to right, 0 = from right to left var blackLeft = 1; // black is left: 1 = true, 0 = false for(var j = 0; j < rowCount; j++){
for(var i = 0; i < columnCount; i++){
ctx.fillStyle = 'rgba(0,0,0,'+ (blackLeft-(1/(columnCount-1)*i))*direction +')';
ctx.fillRect(
(width/columnCount)*i,(height/rowCount)*j,
(width/columnCount),(height/rowCount)
);
}
columnCount *= 2;
direction *= -1;
blackLeft = blackLeft ? 0 : 1;
}
</script> </body></html> </lang>
Julia
<lang Julia>using Gtk, Cairo, ColorTypes
function generategrays(n, screenwidth)
verts = Vector{RGB}()
hwidth = Int(ceil(screenwidth/n))
for x in 00:Int(floor(0xff/(n-1))):0xff
rgbgray = RGB(x/255, x/255, x/255)
for i in 1:hwidth
push!(verts, rgbgray)
end
end
verts
end
function drawline(ctx, p1, p2, color, width)
move_to(ctx, p1.x, p1.y) set_source(ctx, color) line_to(ctx, p2.x, p2.y) set_line_width(ctx, width) stroke(ctx)
end
const can = @GtkCanvas() const win = GtkWindow(can, "Grayscale bars/Display", 400, 400) fullscreen(win) # start full screen, then reduce to regular window in 5 seconds.
draw(can) do widget
ctx = getgc(can)
h = height(can)
w = width(can)
gpoints = generategrays(8, w)
for (i, x) in enumerate(0:w-1)
drawline(ctx, Point(x, 0.25*h), Point(x, 0), gpoints[i], 1)
end
gpoints = reverse(generategrays(16, w))
for (i, x) in enumerate(0:w-1)
drawline(ctx, Point(x, 0.5*h), Point(x, 0.25*h), gpoints[i], 1)
end
gpoints = generategrays(32, w)
for (i, x) in enumerate(0:w-1)
drawline(ctx, Point(x, 0.75*h), Point(x, 0.5*h), gpoints[i], 1)
end
gpoints = reverse(generategrays(64, w))
for (i, x) in enumerate(0:w-1)
drawline(ctx, Point(x, h), Point(x, 0.75*h), gpoints[i], 1)
end
end
show(can) sleep(5) unfullscreen(win) const cond = Condition() endit(w) = notify(cond) signal_connect(endit, win, :destroy) wait(cond)</lang>
Kotlin
<lang scala>// version 1.1
import java.awt.Color import java.awt.Graphics import javax.swing.JFrame
class GreyBars : JFrame("grey bars example!") {
private val w: Int private val h: Int
init {
w = 640
h = 320
setSize(w, h)
defaultCloseOperation = JFrame.EXIT_ON_CLOSE
isVisible = true
}
override fun paint(g: Graphics) {
var run = 0
var colorComp: Double // component of the color
var columnCount = 8
while (columnCount < 128) {
var colorGap = 255.0 / (columnCount - 1) // by this gap we change the background color
val columnWidth = w / columnCount
val columnHeight = h / 4
if (run % 2 == 0) // switches color directions with each iteration of while loop
colorComp = 0.0
else {
colorComp = 255.0
colorGap *= -1.0
}
val ystart = columnHeight * run
var xstart = 0
for (i in 0 until columnCount) {
val iColor = Math.round(colorComp).toInt()
val nextColor = Color(iColor, iColor, iColor)
g.color = nextColor
g.fillRect(xstart, ystart, columnWidth, columnHeight)
xstart += columnWidth
colorComp += colorGap }
run++
columnCount *= 2
}
}
}
fun main(args: Array<String>) {
GreyBars()
}</lang>
Liberty BASIC
Black boxes were added around each color for ease of counting the boxes. <lang lb> nomainwin
WindowWidth =DisplayWidth WindowHeight =DisplayHeight
open "Grey bars" for graphics_fs_nsb as #w
- w "trapclose [quit]"
- w "down"
bars =4 ' alter for more, finer bars.
for group =0 to bars -1
for i = 0 to 2^( 3 +group) -1
#w "place "; WindowWidth *i /( 2^( 3 +group)); " "; WindowHeight *group /bars
if ( group =0) or ( group =2) then
g$ =str$( int( 255 *i /(2^( 3 +group)-1)))
else
g$ =str$( 255 -int( 255 *i /(2^( 3 +group)-1)))
end if
grey$ =g$ +" " +g$ +" " +g$
#w "backcolor "; grey$
'#w "color "; grey$ 'rem out for outlined areas..
#w "boxfilled "; WindowWidth *( i +1) /8 ; " "; WindowHeight *( group +1) /bars
next i
next group
wait [quit] close #w end
</lang> Resulting GreyScale image without the outlines.
Lua
<lang lua>local nw = require("nw") local app = nw:app() local cw, ch = 320, 240 local win = app:window(cw, ch, "Grayscale Bars", false) function win:repaint()
local cr = win:bitmap():cairo()
local ystride = ch/4
for y = 0, 3 do
local i, n = 1, 2^(y+3)
local xstride = cw/n
for x = 0, n-1 do
cr:rectangle(x*xstride, y*ystride, xstride, ystride)
local gray = x / (n-1)
if y%2>0 then gray=1-gray end
cr:rgb(gray, gray, gray)
cr:fill()
end
end
end win:show() app:run()</lang>
Mathematica / Wolfram Language
<lang mathematica>CreateDocument[ Graphics[ Flatten@Table[ { If[EvenQ[#3], GrayLevel[ 1. - j/#1 ], GrayLevel[ j/#1 ]],
Rectangle[{j #2, 7*#3}, {#2 (j + 1), (#3 + 1) 7}]}, {j, 0, #1}] & @@@
{{7, 8, 3}, {15, 4, 2}, {31, 2, 1}, {63, 1, 0} }
,ImageSize -> Full], WindowFrame -> "Frameless", WindowSize -> Full]</lang>
MAXScript
3ds max provides customizable maps like gradient to the user, but you can also write it: <lang MAXScript> fn drawBarRow _bmp _row _width _number _inverse= ( local dir = if _inverse then 1 else -1 if not _inverse then ( setpixels _bmp [0,_row] (for i in 1 to (_width/_number) collect (black)) for i = (_width/_number) to _width by (_width/_number) do ( local loopPosition = i/(_width-(_width/_number)) as float local colorsArr = for c in 1 to (_width/_number) collect (white*loopPosition) setpixels _bmp [i,_row] colorsArr ) return _bmp ) else ( setpixels _bmp [0,_row] (for i in 1 to (_width/_number) collect (white)) for i = _width to (_width/_number) by ((_width/_number)*-1) do ( local loopPosition = 1.0-(i/(_width-(_width/_number))) as float local colorsArr = for c in 1 to (_width/_number) collect (white*loopPosition) setpixels _bmp [i,_row] colorsArr ) return _bmp )
)
fn bitmap_verticalBars = ( local width = (sysinfo.desktopsize).x local height = (sysinfo.desktopsize).y local theBitmap = bitmap width height color:white
local row = 0 while row <= (height-1) do ( local barNumber = 0 case of ( (row < (height/4)): (barNumber = 1) (row >= (height/4) and row < (height/2)): (barNumber = 2) (row >= (height/2) and row < (height-(height/4))): (barNumber = 3) (row >= (height-(height/4))): (barNumber = 4) default: return theBitmap ) case barNumber of ( 1: ( theBitmap = drawBarRow theBitmap row width 8 false ) 2: ( theBitmap = drawBarRow theBitmap row width 16 true ) 3: ( theBitmap = drawBarRow theBitmap row width 32 false ) 4: ( theBitmap = drawBarRow theBitmap row width 64 true ) ) row += 1 -- ) return theBitmap )
b = bitmap_verticalBars() display b </lang>
Nim
<lang Nim>import gintro/[glib, gobject, gtk, gio, cairo]
const
Width = 640 Height = 480
- ---------------------------------------------------------------------------------------------------
proc draw(area: DrawingArea; context: Context) =
## Draw the greyscale bars.
const Black = 0.0 White = 1.0
var y = 0.0 var nrect = 8 let rectHeight = Height / 4
# Draw quarters. for quarter in 0..3: let rectWidth = Width / nrect var x = 0.0 var (grey, incr) = if (quarter and 1) == 0: (Black, 1 / nrect) else: (White, -1 / nrect)
# Draw rectangles.
for _ in 1..nrect:
context.rectangle(x, y, rectWidth, rectHeight)
context.setSource([grey, grey, grey])
context.fill()
x += rectWidth
grey += incr
y += rectHeight nrect *= 2
- ---------------------------------------------------------------------------------------------------
proc onDraw(area: DrawingArea; context: Context; data: pointer): bool =
## Callback to draw/redraw the drawing area contents.
area.draw(context) result = true
- ---------------------------------------------------------------------------------------------------
proc activate(app: Application) =
## Activate the application.
let window = app.newApplicationWindow()
window.setSizeRequest(Width, Height)
window.setTitle("Greyscale bars")
# Create the drawing area. let area = newDrawingArea() window.add(area)
# Connect the "draw" event to the callback to draw the spiral.
discard area.connect("draw", ondraw, pointer(nil))
window.showAll()
- ———————————————————————————————————————————————————————————————————————————————————————————————————
let app = newApplication(Application, "Rosetta.GreyscaleBars") discard app.connect("activate", activate) discard app.run()</lang>
OCaml
<lang ocaml>open Graphics
let round x = truncate (floor (x +. 0.5))
let () =
open_graph "";
let width = size_x ()
and height = size_y () in
let bars = [| 8; 16; 32; 64 |] in
let n = Array.length bars in
Array.iteri (fun i bar ->
let part = float width /. float bar in
let y = (height / n) * (n - i - 1) in
for j = 0 to pred bar do
let x = round (float j *. part) in
let v = round (float j *. 255. /. float (bar - 1)) in
let v = if (i mod 2) = 0 then v else 255 - v in
set_color (rgb v v v);
fill_rect x y (round part) (height / n)
done
) bars;
ignore(read_key())</lang>
Run with:
$ ocaml graphics.cma greyscale_bars.ml
Perl
<lang perl>sub partition {
my($all, $div) = @_; my @marks = 0; push @marks, $_/$div * $all for 1..$div; my @copy = @marks; $marks[$_] -= $copy[$_-1] for 1..$#marks; @marks[1..$#marks];
}
sub bars {
my($h,$w,$p,$rev) = @_; my (@nums,@vals,$line,$d);
$d = 2**$p;
push @nums, int $_/($d-1) * (2**16-1) for $rev ? reverse 0..$d-1 : 0..$d-1;
push @vals, ($nums[$_]) x (partition($w, $d))[$_] for 0..$#nums;
$line = join(' ', @vals) . "\n";
$line x $h;
}
my($w,$h) = (1280,768); open my $pgm, '>', 'Greyscale-bars-perl5.pgm' or die "Can't create Greyscale-bars-perl5.pgm: $!";
print $pgm <<"EOH"; P2
- Greyscale-bars-perl5.pgm
$w $h 65535 EOH
my ($h1,$h2,$h3,$h4) = partition($h,4);
print $pgm
bars($h1,$w,3,0), bars($h2,$w,4,1), bars($h3,$w,5,0), bars($h4,$w,6,1);</lang>
See Greyscale-bars-perl5 (offsite image)
Phix
Resizeable. Use of nx avoids rounding/misalignment errors
You can run this online here.
-- -- demo\rosetta\Greyscale_bars.exw -- =============================== -- with javascript_semantics include pGUI.e Ihandle dlg, canvas cdCanvas cddbuffer, cdcanvas integer quit = 1 bool refire = false function redraw_cb(Ihandle /*ih*/, integer /*posx*/, /*posy*/) cdCanvasActivate(cddbuffer) integer {width, height} = IupGetIntInt(canvas, "DRAWSIZE") integer h = floor(height/4) height -= 1 for row=1 to 4 do integer x = 0, p2 = power(2,row+2), c = floor(255/(p2-1)) for n=0 to p2-1 do integer colour = c*n*#010101 if and_bits(row,1)=0 then colour = xor_bits(colour,#FFFFFF) end if cdCanvasSetForeground(cddbuffer, colour) integer nx = ceil(width*(n+1)/p2) cdCanvasBox(cddbuffer, x, nx-1, (4-row)*h, height) x = nx end for height = (4-row)*h-1 end for cdCanvasFlush(cddbuffer) return IUP_DEFAULT end function function map_cb(Ihandle ih) cdcanvas = cdCreateCanvas(CD_IUP, ih) cddbuffer = cdCreateCanvas(CD_DBUFFER, cdcanvas) return IUP_DEFAULT end function function unmap_cb(Ihandle /*ih*/) cdKillCanvas(cddbuffer) cdKillCanvas(cdcanvas) return IUP_DEFAULT end function procedure main() IupOpen() canvas = IupCanvas("RASTERSIZE=600x400") IupSetCallbacks(canvas, {"MAP_CB", Icallback("map_cb"), "UNMAP_CB", Icallback("unmap_cb"), "ACTION", Icallback("redraw_cb")}) dlg = IupDialog(canvas, `TITLE="Greyscale bars"`) IupShow(dlg) IupSetAttribute(canvas, "RASTERSIZE", NULL) if platform()!=JS then IupMainLoop() IupClose() end if end procedure main()
PicoLisp
<lang PicoLisp>(let Pgm # Create PGM of 384 x 288 pixels
(make
(for N 4
(let L
(make
(for I (* N 8)
(let C (*/ (dec I) 255 (dec (* N 8)))
(unless (bit? 1 N)
(setq C (- 255 C)) )
(do (/ 48 N) (link C)) ) ) )
(do 72 (link L)) ) ) )
(out '(display) # Pipe to ImageMagick
(prinl "P5") # NetPBM format
(prinl (length (car Pgm)) " " (length Pgm))
(prinl 255)
(for Y Pgm (apply wr Y)) ) )</lang>
Plain English
<lang plainenglish>To run: Start up. Clear the screen. Imagine a box with the screen's left and the screen's top and the screen's right and the screen's bottom divided by 4. Make a gradient with the box and 8 and "left-to-right". Draw the gradient. Draw the next gradient given the gradient. Draw the next gradient given the gradient. Draw the next gradient given the gradient. Refresh the screen. Wait for the escape key. Shut down.
A gradient is a record with A box, A partitions number, And a direction string. \"left-to-right" or "right-to-left"
To make a gradient with a box and a number and a string: Put the box into the gradient's box. Put the number into the gradient's partitions. Put the string into the gradient's direction.
To draw a gradient: Put the white color into a color. Put 1000 [the maximum lightness] divided by the gradient's partitions into an amount. If the gradient's direction is "left-to-right", put the black color into the color. Put the gradient's box into a box. Put the gradient's box's width divided by the gradient's partitions into a width number. Put the width plus the box's left into the box's right. Loop. If a counter is past the gradient's partitions, exit. Draw and fill the box with the color. Move the box right the width. If the gradient's direction is "left-to-right", lighten the color by the amount; repeat. Darken the color by the amount. Repeat.
To draw the next gradient given a gradient: Move the gradient's box down the gradient's box's height. Double the gradient's partitions. If the gradient's direction is "left-to-right", set a flag. If the flag is set, put "right-to-left" into the gradient's direction. If the flag is not set, put "left-to-right" into the gradient's direction. Draw the gradient.</lang>
Processing
<lang java> //Aamrun, 3rd July 2022
void drawPanel(int startColour,int endColour,int bars,int startY){
int rectWidth = width / bars,rectHeight = height / 4, startX = 0,increment;
increment = (endColour - startColour)/(bars-1);
for(int i = 0;i < bars;i++){
fill(startColour + i*increment);
rect(startX + i*rectWidth,startY,rectWidth,rectHeight);
}
}
void setup(){
size(1280,960); drawPanel(0,255,8,0); drawPanel(255,0,16,height/4); drawPanel(0,255,32,height/2); drawPanel(255,0,64,3*height/4);
} </lang>
PureBasic
<lang PureBasic>EnableExplicit
Macro Check(Function)
If Not Function : End : EndIf
EndMacro
Check(InitKeyboard()) ; Cannot initialize keyboard Check(InitSprite()) ; Cannot initialize sprite/screen library Check(ExamineDesktops()) ; Cannot retrieve informations about desktops
Define.i iHeight, iWidth, iDepth iHeight = DesktopHeight(0) iWidth = DesktopWidth(0) iDepth = DesktopDepth(0)
If OpenScreen(iWidth, iHeight, iDepth, "Press ENTER to exit")
Define.i bMode.b, iLines, fLine.f, iRow, iSpans, fSpan.f,
fColor.f, iTop, iWide, iHigh, iCol, iShade
If StartDrawing(ScreenOutput())
bMode = #True ; Pow = #True; Add = #False iLines = 4 ; Number of Lines
If iLines < 1 : iLines = 1 : EndIf ; Pow/Add-Min
If bMode
If iLines > 6 : iLines = 6 : EndIf ; Pow-Max
Else
If iLines > 32 : iLines = 32 : EndIf ; Add-Max
EndIf
fLine = iHeight / iLines
iLines - 1
For iRow = 0 To iLines
If bMode
iSpans = Pow(2, iRow + 3) - 1 ; Pow: 8, 16, 32, 64, 128, 256
Else
iSpans = (iRow + 1) * 8 - 1 ; Add: 8, 16, 24, 32, 40, 48, ...
EndIf
fSpan = iWidth / (iSpans + 1)
fColor = 255 / iSpans
iTop = Round(iRow * fLine, #PB_Round_Up)
iWide = Round(fSpan, #PB_Round_Up)
iHigh = Round(fLine, #PB_Round_Up)
For iCol = 0 To iSpans
iShade = Round(fColor * iCol, #PB_Round_Nearest)
If iRow % 2 <> 0 : iShade = 255 - iShade : EndIf ; Alternation
Box(Round(iCol * fSpan, #PB_Round_Up), iTop, iWide, iHigh,
RGB(iShade, iShade, iShade))
Next
Next
StopDrawing() FlipBuffers()
Repeat
Delay(30)
ExamineKeyboard()
Until KeyboardPushed(#PB_Key_Escape) Or
KeyboardPushed(#PB_Key_Return)
EndIf
CloseScreen()
EndIf End</lang> Press Enter or Escape to exit the programs's display.
Python
<lang Python>#!/usr/bin/env python
- four gray scaled stripes 8:16:32:64 in Python 2.7.1
from livewires import *
horiz=640; vert=480; pruh=vert/4; dpp=255.0 begin_graphics(width=horiz,height=vert,title="Gray stripes",background=Colour.black)
def ty_pruhy(each): hiy=each[0]*pruh; loy=hiy-pruh krok=horiz/each[1]; piecol=255.0/(each[1]-1) for x in xrange(0,each[1]): barva=Colour(piecol*x/dpp,piecol*x/dpp,piecol*x/dpp ); set_colour(barva) if each[2]: box(x*krok,hiy,x*krok+krok,loy,filled=1) else: box(horiz-x*krok,hiy,horiz-((x+1)*krok),loy,filled=1)
- main
source=[[4,8,True],[3,16,False],[2,32,True],[1,64,False]] for each in source: ty_pruhy(each)
while keys_pressed() != [' ']: # press spacebar to close window pass </lang>
R
Create a 4x64 matrix representing the described pattern, set margins to 0 so the image will fill the display, and plot the matrix in grayscale using the "image" function:
<lang R> mat <- matrix(c(rep(1:8, each = 8) / 8,
rep(16:1, each = 4) / 16,
rep(1:32, each = 2) / 32,
rep(64:1, each = 1) / 64),
nrow = 4, byrow = TRUE)
par(mar = rep(0, 4)) image(t(mat[4:1, ]), col = gray(1:64/64), axes = FALSE) </lang>
Or, this can be generalized with the function below, which produces the pattern for an arbitrary number of rows (though rows become visibly indistinguishable after about row 5):
<lang R> grayscalesImage <- function(nrow = 4) {
X <- matrix(NA, nrow = nrow, ncol = 2^(nrow + 2))
for (i in 1:nrow) {
X[i, ] <- rep(1:2^(i + 2), each = 2^(nrow - i)) / 2^(i + 2)
if (i %% 2 == 0) X[i, ] <- rev(X[i, ])
}
par(mar = rep(0, 4))
image(t(X[nrow:1, ]), col = gray(1:ncol(X) / ncol(X)), axes = FALSE)
}
- Example ##
grayscalesImage(6) # produces image shown in screenshot to the right </lang>
Racket
This solution uses the built-in pict library for graphics.
<lang racket>
- lang racket/gui
(require slideshow/pict)
(define-values (*width* *height*) (values 400 40))
(define (shades inc)
(for/list ([scale (in-range 0 (+ 1 inc) inc)]) (round (* 255 scale))))
(define (grays increment direction)
(define colors (shades increment))
(apply hc-append
((if (eq? direction 'right) identity reverse)
(for/list ([c colors])
(colorize (filled-rectangle
(/ *width* (length colors)) *height*)
(make-color c c c))))))
(vc-append (grays 1/8 'right) (grays 1/16 'left)
(grays 1/32 'right) (grays 1/64 'left))
</lang>
Raku
(formerly Perl 6) <lang perl6>my ($width,$height) = 1280,768;
my $PGM = open "Greyscale-bars-perl6.pgm", :w orelse die "Can't create Greyscale-bars-perl6.pgm: $_";
$PGM.print: qq:to/EOH/;
P2 # Greyscale-bars-perl6.pgm $width $height 65535 EOH
my ($h1,$h2,$h3,$h4) = divvy($height,4);
my @nums = ((0/7,1/7...7/7) X* 65535)».floor; my $line = ~(@nums Zxx divvy($width,8)); $PGM.say: $line for ^$h1;
@nums = ((15/15,14/15...0/15) X* 65535)».floor; $line = ~(@nums Zxx divvy($width,16)); $PGM.say: $line for ^$h2;
@nums = ((0/31,1/31...31/31) X* 65535)».floor; $line = ~(@nums Zxx divvy($width,32)); $PGM.say: $line for ^$h3;
@nums = ((63/63,62/63...0/63) X* 65535)».floor; $line = ~(@nums Zxx divvy($width,64)); $PGM.say: $line for ^$h4;
$PGM.close;
sub divvy($all, $div) {
my @marks = ((1/$div,2/$div ... 1) X* $all)».round; @marks Z- 0,|@marks;
}</lang> See Greyscale-bars-perl6 (offsite image)
RapidQ
<lang vb> Declare Sub PaintCanvas
Create Form as Qform
Caption = "Rosetta Greyscale"
Center
create Canv as QCanvas
align = 5
onPaint = PaintCanvas
end create
end create
Sub PaintCanvas
NumRows = 4 'Change for number of rows
for curbar = 0 to NumRows-1
Bars = 2^(curbar+3)
for x = 0 to (Bars -1)
x1=Canv.Width/Bars*x
y1=Canv.Height/NumRows*CurBar
x2=Canv.Width/Bars*(x+1)
y2=Canv.Height/NumRows*(CurBar+1)
c=(255/(Bars-1))*x
c=iif(curbar mod 2, 255-c, c)
Canv.FillRect(x1, y1, x2, y2, rgb(c, c, c))
next x
next curbar
end sub
Form.showmodal </lang>
Ring
<lang ring>
- Project : Greyscale bars/Display
load "guilib.ring"
paint = null
new qapp
{
win1 = new qwidget() {
setwindowtitle("Greyscale bars/Display")
setgeometry(100,100,500,600)
label1 = new qlabel(win1) {
setgeometry(10,10,400,400)
settext("")
}
new qpushbutton(win1) {
setgeometry(150,500,100,30)
settext("draw")
setclickevent("draw()")
}
show()
}
exec()
}
func draw
p1 = new qpicture()
color = new qcolor() {
setrgb(0,0,255,255)
}
pen = new qpen() {
setcolor(color)
setwidth(1)
}
paint = new qpainter() {
begin(p1)
setpen(pen)
for row=1 to 4
n=pow(2,(row+2))
w=1280/n
py=256*(4-row)
for b=0 to n-1
g=floor(255*b/(n-1))
if n=16 or n=64
g=255-g
ok
color2 = new qcolor()
color2.setrgb(g,g,g,255)
mybrush = new qbrush() {setstyle(1) setcolor(color2)}
paint.setbrush(mybrush)
paint.drawrect(w*b,py,w,256)
next
next
endpaint()
}
label1 { setpicture(p1) show() }
</lang> Output: https://www.dropbox.com/s/01iywg04iwubf55/GreyscaleBars.jpg?dl=0
Run BASIC
<lang Runbasic>for i = 1 to 4 incr = int(256 / (i * 8)) c = 256
html "
" for j = 1 to i * 8 html ""c = c - incr next j
html "" next i html ""
end</lang>
Run in a browser
Scala
<lang scala>import scala.swing._
class GreyscaleBars extends Component {
override def paintComponent(g:Graphics2D)={
val barHeight=size.height>>2
for(run <- 0 to 3; colCount=8<<run){
val deltaX=size.width.toDouble/colCount
val colBase=if (run%2==0) -255 else 0
for(x <- 0 until colCount){
val col=(colBase+(255.0/(colCount-1)*x).toInt).abs
g.setColor(new Color(col,col,col))
val startX=(deltaX*x).toInt
val endX=(deltaX*(x+1)).toInt
g.fillRect(startX, barHeight*run, endX-startX, barHeight)
}
}
}
}</lang> Open window:
<lang scala>new MainFrame(){
title="Greyscale bars" visible=true preferredSize=new Dimension(640, 320) contents=new GreyscaleBars()
}</lang>
Seed7
<lang seed7>$ include "seed7_05.s7i";
include "draw.s7i"; include "keybd.s7i";
const proc: main is func
local
var integer: barHeight is 0;
var integer: barNumber is 0;
var integer: colCount is 0;
var integer: deltaX is 0;
var integer: x is 0;
var integer: col is 0;
begin
screen(640, 480);
KEYBOARD := GRAPH_KEYBOARD;
barHeight := height(curr_win) div 4;
for barNumber range 0 to 3 do
colCount := 8 << barNumber;
deltaX := width(curr_win) div colCount;
for x range 0 to pred(colCount) do
if barNumber rem 2 = 0 then
col := 65535 - 65535 div pred(colCount) * x;
else
col := 65535 div pred(colCount) * x;
end if;
rect(deltaX * x, barHeight * barNumber, deltaX, barHeight,
color(col, col, col));
end for;
end for;
ignore(getc(KEYBOARD));
end func;</lang>
Tcl
<lang tcl>package require Tcl 8.5 package require Tk 8.5
wm attributes . -fullscreen 1 pack [canvas .c -highlightthick 0] -fill both -expand 1
- Add more values into this to do more greyscale bar variations
set splits {8 16 32 64} set dy [expr {[winfo screenheight .c] / [llength $splits]}] set y 0 foreach s $splits {
set dx [expr {double([winfo screenwidth .c]) / $s}]
set dc [expr {double(0xFF) / ($s-1)}]
for {set i 0} {$i < $s} {incr i} {
set c [expr {int($i * $dc)}] set x [expr {int($i * $dx)}] .c create rectangle $x $y [expr {$x+$dx+1}] [expr {$y+$dy+1}] \
-fill [format "#%02x%02x%02x" $c $c $c] -outline {}
}
incr y $dy
}</lang>
Wren
<lang ecmascript>import "graphics" for Canvas, Color import "dome" for Window import "math" for Math
class GreyBars {
construct new(width, height) {
Window.title = "Grey bars example"
Window.resize(width, height)
Canvas.resize(width, height)
_w = width
_h = height
}
init() {
drawBars()
}
drawBars() {
var run = 0
var colorComp = 0 // component of the color
var columnCount = 8
while (columnCount < 128) {
var colorGap = 255 / (columnCount - 1) // by this gap we change the background color
var columnWidth = (_w / columnCount).floor
var columnHeight = (_h / 4).floor
if (run % 2 == 0) { // switches color directions with each iteration of while loop
colorComp = 0
} else {
colorComp = 255
colorGap = -colorGap
}
var ystart = columnHeight * run
var xstart = 0
for (i in 0...columnCount) {
var iColor = Math.round(colorComp)
var nextColor = Color.rgb(iColor, iColor, iColor)
Canvas.rectfill(xstart, ystart, xstart + columnWidth, ystart + columnHeight, nextColor)
xstart = xstart + columnWidth
colorComp = colorComp + colorGap }
run = run + 1
columnCount = columnCount * 2
}
}
update() {}
draw(alpha) {}
}
var Game = GreyBars.new(640, 320)</lang>
XPL0
Floating point is used to get the full range of black to white.
<lang XPL0>include c:\cxpl\codes; \intrinsic 'code' declarations int Q, N, W, B, C, Y; [SetVid($112); \640x480x24 graphics for Q:= 0 to 4-1 do \quarter of screen
[N:= 8<<Q; \number of bars
W:= 640/N; \width of bar (pixels)
for B:= 0 to N-1 do \for each bar...
[C:= fix(255.0/float(N-1) * float(if Q&1 then N-1-B else B));
C:= C<<16 + C<<8 + C; \RGB color = gray
for Y:= Q*120 to (Q+1)*120-1 do
[Move(W*B, Y); Line(W*(B+1)-1, Y, C)];
];
];
Q:= ChIn(1); \wait for keystroke SetVid(3); \restore normal text mode ]</lang>
Yabasic
<lang Yabasic>open window 1024, 600 w = peek("winwidth") h = peek("winheight") rows = 4 hd = int(h / rows) mitad = 0
for row = 1 to rows
if not mitad then
wd = int(w / (8 * row))
mitad = wd
else
mitad = mitad / 2
end if
c = 255 / (w / mitad)
for n = 0 to (w / mitad)
color 255 - c * n, 255 - c * n, 255 - c * n
if mod(row, 2) = 0 color c * n, c * n, c * n
fill rectangle mitad * n, hd * (row - 1), mitad * (n+1), hd * row
pause .1
next n
next row</lang>
zkl
Draws to a PPM file, not the screen, assumes a 640/480 display.
Uses the PPM class from http://rosettacode.org/wiki/Bitmap/Bresenham%27s_line_algorithm#zkl <lang zkl>img:=PPM(640,480); foreach q in ([0..3]){ //quarter of screen
n:=(8).shiftLeft(q); //number of bars
w:=640/n; //width of bar (pixels)
foreach b in ([0..n-1]){ //for each bar...
c:=(255.0/(n-1).toFloat() * (if(q.isOdd) n-1-b else b)).toInt();
c:=c.shiftLeft(16) + c.shiftLeft(8) + c; //RGB color = gray
foreach y in ([(3-q)*120 .. (3-q+1)*120-1]){ // flip image vertically
img.line(w*b,y, w*(b+1)-1,y, c);
}
}
} img.write(File("foo.ppm","wb"));</lang>
- Output:
Same as the R image (but smaller): http://www.zenkinetic.com/Images/RosettaCode/grayscaleBars.jpg
ZX Spectrum Basic
ZX Spectrum Basic cannot natively produce greyscale. However, the colours have been cleverly arranged, so that the native colours give monochrome signals in sequential order of brightness. Wind the colour down, or use a black and white television and we have a set of 8 bars:
<lang zxbasic>10 REM wind the colour down or use a black and white television to see greyscale bars 20 REM The ZX Spectrum display is 32 columns wide, so we have 8 columns of 4 spaces 25 BORDER 0: CLS 30 FOR r=0 TO 21: REM There are 22 rows 40 FOR c=0 TO 7: REM We use the native colour sequence here 50 PRINT PAPER c;" ";: REM four spaces, the semicolon prevents newline 60 NEXT c 70 REM at this point the cursor has wrapped, so we don't need a newline 80 NEXT r</lang>
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