# Greyscale bars/Display

(Redirected from Contrast bars/Display)
Greyscale bars/Display
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

```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();
}
}
}
}
```

Library: GTK
```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_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;
```

## Amazing Hopper

Translation of: AWK

Version: hopper-FLOW!

```#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```

## AutoHotkey

Requires the GDI+ Standard Library by tic: http://www.autohotkey.com/forum/viewtopic.php?t=32238

```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)
}
```

## 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++
}
}
```

## BASIC

### ANSI BASIC

Translation of: BBC BASIC
Works with: Decimal 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
```

### BASIC256

```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
```

### BBC BASIC

```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%
```

## C

Library: GTK
```#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;
}
```

## C#

```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;
}
}
```

## C++

using Qt 4.6

```file greytones.h
```
```#ifndef MYWIDGET_H
#define MYWIDGET_H
#include <QWidget>

class QPaintEvent ;

class MyWidget : public QWidget {
public :
MyWidget( ) ;

protected :
void paintEvent( QPaintEvent * ) ;
} ;
#endif
```
`file greytones.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 ;
}
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++ ;
}
}
```
```file main.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( ) ;
}
```

## Component Pascal

```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

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
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"```

## Delphi

Works with: Delphi version 6.0

Uses Delphi graphic objects to create a subroutine which draws rows of bars according to specificification for number of bars and rows, the row number and the direction of the color graident.

```procedure DrawBar(Image: TImage; Bars,Rows,Row: integer; WhiteToBlack: boolean);
{Draw horizontal bar according the following parameters:}
{Bars = number of color bars to fit into the horizontal space}
{Rows = number of rows to fit into the vertical space}
{Row = the row to place the current bar - numbered 0..n, top to bottom}
{WhiteToBlack - if true, bars in the row go from white to back}
var X: integer;
var Color: integer;
var ColorStep: double;
var BarHeight: integer;
var R,R2: TRect;
begin
{Calculate bar dimensions}
BarHeight:=Image.Height div Rows;
R:=Rect(0,0,(Image.Width div Bars)+1, BarHeight);
OffsetRect(R,0,BarHeight * Row);
R2:=R;
{Calculate color parameters}
ColorStep:=255/(Bars-1);
if WhiteToBlack then
begin
Color:=255;
ColorStep:=-ColorStep
end
else Color:=0;
{Draw bars}
for X:=1 to Bars do
begin
{Set color}
Image.Canvas.Brush.Color:=RGB(Color,Color,Color);
Image.Canvas.Pen.Color:=RGB(Color,Color,Color);
{Draw rectangular bar}
Image.Canvas.Rectangle(R2);
{Move rectangle and calculate color}
OffsetRect(R2,R.Right,0);
Color:=Round(X * ColorStep);
end;
end;

procedure ShowGrayBars(Image: TImage);
{Draw four bar, with alternating color scheme}
begin
DrawBar(Image,8,4,0,False);
DrawBar(Image,16,4,1,True);
DrawBar(Image,32,4,2,False);
DrawBar(Image,64,4,3,True);
end;
```
Output:

## EasyLang

```n = 8
for row = 0 to 3
sz = 100 / n
for i = 0 to n - 1
c = i / (n - 1)
if row mod 2 = 1
c = 1 - c
.
color3 c c c
move sz * i 75 - row * 25
rect sz + 1 25
sleep 0.02
.
n *= 2
.
```

## 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	--| width of each rectangle; number of rectangles on this row
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	--| From `white' to `black' or ...
up: INTEGER = 1		--| From `black' to `white'
```

## 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:```

## 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```

## 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
}
}```

## 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```
Output:
```[See accompanying screenshot.]
```

And here's another clever and shorter solution:

```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```

## 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```

## Go

Library: Go Graphics
Translation of: Java
```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")
}
```
Output:
```Image similar to R entry (first image)
```

This program uses an inlined XPM file which is scaled to fill an entire GTK fullscreen window

```import Graphics.UI.Gtk
import Graphics.UI.Gtk.Gdk.GC

-- click on the window to exit.

main = do
initGUI

window <- windowNew

buf <- pixbufNewFromXPMData bars

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",
"*+.9876543210zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCA"
]
```

## 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.

```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
```

## J

Solution:

```   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
```

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

```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( ) ;
}
}
```

## 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>
```

## 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)
```

## Kotlin

Translation of: Java
```// 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()
}
```

## Liberty BASIC

Black boxes were added around each color for ease of counting the boxes.

```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```

Resulting GreyScale image without the outlines.

## Lua

Library: nw
Library: cairo
```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()
```

## Mathematica / Wolfram Language

```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]
```

## MAXScript

3ds max provides customizable maps like gradient to the user, but you can also write it:

```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```

## Nim

Library: gintro
```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()

# Connect the "draw" event to the callback to draw the spiral.

window.showAll()

#———————————————————————————————————————————————————————————————————————————————————————————————————

let app = newApplication(Application, "Rosetta.GreyscaleBars")
```

## 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;
```

Run with:

`\$ ocaml graphics.cma greyscale_bars.ml`

## 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);
```

See Greyscale-bars-perl5 (offsite image)

## Phix

Resizeable. Use of nx avoids rounding/misalignment errors

Library: Phix/pGUI
Library: Phix/online

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

```(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)) ) )```

## Plain English

```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".
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.

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.

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.

## Processing

```//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);
}
```

## 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,
Next
Next

StopDrawing()
FlipBuffers()

Repeat
Delay(30)
ExamineKeyboard()
Until KeyboardPushed(#PB_Key_Escape) Or
KeyboardPushed(#PB_Key_Return)
EndIf
CloseScreen()
EndIf
End```

Press Enter or Escape to exit the programs's display.

## Python

Library: livewires
```#!/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
```

## Quackery

```  [ \$ "turtleduck.qky" loadfile ] now!

[ 1280 1 ]                  is width          (     --> s )
[ 720 1 ]                   is height         (     --> s )

[ dip [ 1 - dup ]
255 * swap /
1 swap
3 of dup colour fill
[ 2 times
[ width 2over v/ walk
-1 4 turn
height 4 1 v/ walk
-1 4 turn ]
2drop ] ]             is bar            ( n n -->   )

[ 1 over times
[ over i bar
width 2over v/ fly ]
2drop ]                   is line           (   n -->   )

[ turtle
10 frames
width 2 1 v/ fly
1 4 turn
height 2 1 v/ fly
1 2 turn
height fly
-1 4 turn
' [ 8 16 32 64 ]
2 times
1 4 turn
height -2 1 v/ fly
1 4 turn
1 2 turn ]
drop
1 frames ]                is greyscale-bars (     -->   )

greyscale-bars```
Output:

## 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:

```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)
```

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):

```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
```

## Racket

This solution uses the built-in pict library for graphics.

```#lang racket/gui
(require slideshow/pict)

(define-values (*width* *height*) (values 400 40))

(for/list ([scale (in-range 0 (+ 1 inc) inc)])
(round (* 255 scale))))

(define (grays increment direction)
(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))
```

## Raku

(formerly Perl 6)

```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;
}
```

See Greyscale-bars-perl6 (offsite image)

## RapidQ

```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```

## Ring

```# Project : Greyscale bars/Display

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() }```

## Run BASIC

```for i = 1 to 4
incr	= int(256 / (i * 8))
c	= 256
html "<table style='width: 200px; height: 11px;' border=0 cellpadding=0 cellspacing=0><tr>"
for j = 1 to i * 8
html "<td style='background-color: rgb(";c;",";c;",";c;");'></td>"
c = c - incr
next j
html "</tr>"
next i
html "</table>"
end```
`Run in a browser`

## 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)
}
}
}
}
```

Open window:

```new MainFrame(){
title="Greyscale bars"
visible=true
preferredSize=new Dimension(640, 320)
contents=new GreyscaleBars()
}
```

## 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;```

## Tcl

Library: Tk
```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
}
```

## Wren

Library: DOME
```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)
```

## XPL0

Floating point is used to get the full range of black to white.

```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
]```

## Yabasic

```open window 1024, 600
w = peek("winwidth")
h = peek("winheight")
rows = 4
hd = int(h / rows)

for row = 1 to rows
wd = int(w / (8 * row))
else
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```

## zkl

Draws to a PPM file, not the screen, assumes a 640/480 display.

Translation of: XPL0

Uses the PPM class from http://rosettacode.org/wiki/Bitmap/Bresenham%27s_line_algorithm#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"));```
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:

```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```