# Color wheel

Color wheel
You are encouraged to solve this task according to the task description, using any language you may know.

Write a function to draw a HSV color wheel completely with code.

This is strictly for learning purposes only. It's highly recommended that you use an image in an actual application to actually draw the color wheel   (as procedurally drawing is super slow). This does help you understand how color wheels work and this can easily be used to determine a color value based on a position within a circle.

## Applesoft BASIC

The lo-resolution GRaphics screen is limited to 16 colors. Ordered dithering is used for the saturation. Pink is mixed with violet and magenta, and aqua is mixed with light blue and green. These lighter colors are randomly mixed with the saturation dither. Note that the four Apple II colors can be seen at the 90 degree marks: orange at 30 degrees, green at 120 degrees, cyan (blue) at 210 degrees, and violet at 300 degrees.

``` 100  LET R = 3.1415926535 / 180
110  LET YO = 20
120  LET XO = YO
130  LET MS =  INT (YO * 7 / 8)
140  LET O\$ = "1111111111.1111111110.1111011110.1101110110.1101010110.1010101010.0010101001.0010001001.0000100001.0000000001.0000000000"
150  GR
160  FOR S = 0 TO MS
170      LET D = S / MS
180      LET P\$ =  MID\$ (O\$, INT (D * 10) * 11 + 1,11)
190      LET SY = S
200      LET SX = S * 4 / 7
210      LET P = 0
220      FOR I = 0 TO 360
230          LET X = XO +  SIN (I * R) * SX
240          LET Y = YO +  COS (I * R) * SY
250          LET W = 15
260          IF I >  = 30 - 22.4 AND I < 30 + 22.5 THEN  COLOR= 9
270          IF I >  = 75 - 22.5 AND I < 75 + 22.5 THEN  COLOR= 13
280          IF I >  = 120 - 22.5 AND I < 120 + 22.5 THEN  COLOR= 12:W = 14
290          IF I >  = 165 - 22.5 AND I < 165 + 22.5 THEN  COLOR= 7:W = 14
300          IF I >  = 210 - 22.5 AND I < 210 + 22.5 THEN  COLOR= 6
310          IF I >  = 255 - 22.5 AND I < 255 + 22.5 THEN  COLOR= 2
320          IF I >  = 300 - 22.5 AND I < 300 + 22.5 THEN  COLOR= 3:W = 11
330          IF I >  = 345 - 22.5 OR I < 345 + 22.5 - 360 THEN  COLOR= 1:W = 11
340          IF D < .2 THEN W = 15
350          IF  RND (1) < D THEN W = 15
360          IF  VAL ( MID\$ (P\$,P + 1,1)) THEN  COLOR= W
370          IF  SCRN( X,Y) = 0 THEN  PLOT X,Y:P = P + 1: IF P >  = 9 THEN P = 0
380  NEXT I,S```

## AppleScript

```
choose color default color {0, 0, 0, 0}
```

## C++

Library: Qt

This program draws an HSV color wheel in a window.

```// colorwheelwidget.cpp
#include "colorwheelwidget.h"
#include <QPainter>
#include <QPaintEvent>
#include <cmath>

namespace {

QColor hsvToRgb(int h, double s, double v) {
double hp = h/60.0;
double c = s * v;
double x = c * (1 - std::abs(std::fmod(hp, 2) - 1));
double m = v - c;
double r = 0, g = 0, b = 0;
if (hp <= 1) {
r = c;
g = x;
} else if (hp <= 2) {
r = x;
g = c;
} else if (hp <= 3) {
g = c;
b = x;
} else if (hp <= 4) {
g = x;
b = c;
} else if (hp <= 5) {
r = x;
b = c;
} else {
r = c;
b = x;
}
r += m;
g += m;
b += m;
return QColor(r * 255, g * 255, b * 255);
}

}

ColorWheelWidget::ColorWheelWidget(QWidget *parent)
: QWidget(parent) {
setWindowTitle(tr("Color Wheel"));
resize(400, 400);
}

void ColorWheelWidget::paintEvent(QPaintEvent *event) {
QPainter painter(this);
painter.setRenderHint(QPainter::Antialiasing);
const QColor backgroundColor(0, 0, 0);
const QColor white(255, 255, 255);
painter.fillRect(event->rect(), backgroundColor);
const int margin = 10;
const double diameter = std::min(width(), height()) - 2*margin;
QPointF center(width()/2.0, height()/2.0);
QRectF rect(center.x() - diameter/2.0, center.y() - diameter/2.0,
diameter, diameter);
for (int angle = 0; angle < 360; ++angle) {
QColor color(hsvToRgb(angle, 1.0, 1.0));
QPen pen(brush, 1.0);
painter.setPen(pen);
painter.setBrush(brush);
painter.drawPie(rect, angle * 16, 16);
}
}
```
```// colorwheelwidget.h
#ifndef COLORWHEELWIDGET_H
#define COLORWHEELWIDGET_H

#include <QWidget>

class ColorWheelWidget : public QWidget {
Q_OBJECT
public:
ColorWheelWidget(QWidget *parent = nullptr);
protected:
void paintEvent(QPaintEvent *event) override;
};

#endif // COLORWHEELWIDGET_H
```
```// main.cpp
#include "colorwheelwidget.h"
#include <QApplication>

int main(int argc, char *argv[]) {
QApplication app(argc, argv);
ColorWheelWidget widget;
widget.show();
return app.exec();
}
```
Output:

## C#

```// constructor of main window
// in MainWindow.xaml just create <Image Name="imgMain" />
public MainWindow()
{
InitializeComponent();
RenderOptions.SetBitmapScalingMode(imgMain, BitmapScalingMode.HighQuality);
imgMain.Source = new WriteableBitmap(480, 480, 96, 96, PixelFormats.Bgr32, null);
// using slider you can change saturation and call DrawHue with different level
DrawHue(100);
}

void DrawHue(int saturation)
{
var bmp = (WriteableBitmap)imgMain.Source;

int centerX = (int)bmp.Width / 2;
int centerY = (int)bmp.Height / 2;

bmp.Lock();
unsafe{
var buf = bmp.BackBuffer;
IntPtr pixLineStart;
for(int y=0; y < bmp.Height; y++){
pixLineStart = buf + bmp.BackBufferStride * y;
double dy = (y - centerY);
for(int x=0; x < bmp.Width; x++){
double dx = (x - centerX);
double dist = Math.Sqrt(dx * dx + dy * dy);
double theta = Math.Atan2(dy, dx);
double hue = (theta + Math.PI) / (2.0 * Math.PI);
*((int*)(pixLineStart + x * 4)) = HSB_to_RGB((int)(hue * 360), saturation, 100);
}
}
}
}
bmp.Unlock();
}

static int HSB_to_RGB(int h, int s, int v)
{
var rgb = new int[3];

var baseColor = (h + 60) % 360 / 120;
var shift = (h + 60) % 360 - (120 * baseColor + 60 );
var secondaryColor = (baseColor + (shift >= 0 ? 1 : -1) + 3) % 3;

//Setting Hue
rgb[baseColor] = 255;
rgb[secondaryColor] = (int) ((Math.Abs(shift) / 60.0f) * 255.0f);

//Setting Saturation
for (var i = 0; i < 3; i++)
rgb[i] += (int) ((255 - rgb[i]) * ((100 - s) / 100.0f));

//Setting Value
for (var i = 0; i < 3; i++)
rgb[i] -= (int) (rgb[i] * (100-v) / 100.0f);

return RGB2int(rgb[0], rgb[1], rgb[2]);
}

public static int RGB2int(int r, int g, int b) => r << 16 | g << 8 | b;
```
Output:

## Delphi

Library: System.Math
Translation of: Kotlin
```program Color_wheel;

{\$APPTYPE CONSOLE}

uses
Winapi.Windows,
System.SysUtils,
Vcl.Graphics,
System.Math,
Vcl.Imaging.pngimage;

const
TAU = 2 * PI;

function HSBtoColor(hue, sat, bri: Double): TColor;
var
f, h: Double;
u, p, q, t: Byte;
begin
u := Trunc(bri * 255 + 0.5);
if sat = 0 then
Exit(rgb(u, u, u));

h := (hue - Floor(hue)) * 6;
f := h - Floor(h);
p := Trunc(bri * (1 - sat) * 255 + 0.5);
q := Trunc(bri * (1 - sat * f) * 255 + 0.5);
t := Trunc(bri * (1 - sat * (1 - f)) * 255 + 0.5);

case Trunc(h) of
0:
result := rgb(u, t, p);
1:
result := rgb(q, u, p);
2:
result := rgb(p, u, t);
3:
result := rgb(p, q, u);
4:
result := rgb(t, p, u);
5:
result := rgb(u, p, q);
else
result := clwhite;
end;

end;

function ColorWheel(Width, Height: Integer): TPngImage;
var
Center: TPoint;
x, y: Integer;
Hue, dy, dx, dist, theta: Double;
Bmp: TBitmap;
begin
Bmp := TBitmap.Create;
Bmp.SetSize(Width, Height);
with Bmp.Canvas do
begin
Brush.Color := clWhite;
FillRect(ClipRect);
Center := ClipRect.CenterPoint;
for y := 0 to Height - 1 do
begin
dy := y - Center.y;
for x := 0 to Width - 1 do
begin
dx := x - Center.x;
dist := Sqrt(Sqr(dx) + Sqr(dy));
begin
theta := ArcTan2(dy, dx);
Hue := (theta + PI) / TAU;
Pixels[x, y] := HSBtoColor(Hue, 1, 1);
end;
end;
end;
end;

Result := TPngImage.Create;
Result.Assign(Bmp);
Bmp.Free;
end;

begin
with ColorWheel(500, 500) do
begin
SaveToFile('ColorWheel.png');
Free;
end;
end.
```
Output:

Png Image [1].

## EasyLang

Translation of: Go
```proc hsb2rgb hue sat bri . r g b .
h = (hue - floor hue) * 6
f = h - floor h
p = bri * (1 - sat)
q = bri * (1 - sat * f)
t = bri * (1 - sat * (1 - f))
h = floor h
if h = 0
r = bri ; g = t ; b = p
elif h = 1
r = q ; g = bri ; b = p
elif h = 2
r = p ; g = bri ; b = t
elif h = 3
r = p ; g = q ; b = bri
elif h = 4
r = t ; g = p ; b = bri
else
r = bri ; g = p ; b = q
.
.
proc cwheel . .
for y = 0 to 499
dy = y - 250
for x = 0 to 499
dx = x - 250
dist = sqrt (dx * dx + dy * dy)
if dist <= 250
theta = atan2 dy dx
hue = (theta + 180) / 360
hsb2rgb hue (dist / 250) 1 r g b
color3 r g b
move x / 5 y / 5
rect 0.3 0.3
.
.
.
.
cwheel```

## Fōrmulæ

Fōrmulæ programs are not textual, visualization/edition of programs is done showing/manipulating structures but not text. Moreover, there can be multiple visual representations of the same program. Even though it is possible to have textual representation —i.e. XML, JSON— they are intended for storage and transfer purposes more than visualization and edition.

Programs in Fōrmulæ are created/edited online in its website.

In this page you can see and run the program(s) related to this task and their results. You can also change either the programs or the parameters they are called with, for experimentation, but remember that these programs were created with the main purpose of showing a clear solution of the task, and they generally lack any kind of validation.

Solution

Test case

Generating a color wheel of 300x300 pixels:

## FreeBASIC

```#include "fbgfx.bi"

Sub HSVtoRGB(h As Single, s As Integer, v As Integer, Byref r As Integer, Byref g As Integer, Byref b As Integer)
If s = 0 Then
r = v
g = v
b = v
Return
End If

h = h Mod 360
Dim As Single hue = h

Select Case h
Case 0f To 51.5f
hue = ((hue         ) * (30f / (51.5f          )))
Case 51.5f To 122f
hue = ((hue -  51.5f) * (30f / (122f   -  51.5f))) + 30
Case 122f To 142.5f
hue = ((hue -   122f) * (30f / (142.5f -   122f))) + 60
Case 142.5f To 165.5f
hue = ((hue - 142.5f) * (30f / (165.5f - 142.5f))) + 90
Case 165.5f To 192f
hue = ((hue - 165.5f) * (30f / (192f   - 165.5f))) + 120
Case 192f To 218.5f
hue = ((hue -   192f) * (30f / (218.5f -   192f))) + 150
Case 218.5f To 247f
hue = ((hue - 218.5f) * (30f / (247f   - 218.5f))) + 180
Case 247f To 275.5f
hue = ((hue -   247f) * (30f / (275.5f -   247f))) + 210
Case 275.5f To 302.5f
hue = ((hue - 275.5f) * (30f / (302.5f - 275.5f))) + 240
Case 302.5f To 330f
hue = ((hue - 302.5f) * (30f / (330f   - 302.5f))) + 270
Case 330f To 344.5f
hue = ((hue -   330f) * (30f / (344.5f -   330f))) + 300
Case 344.5f To 360f
hue = ((hue - 344.5f) * (30f / (360f   - 344.5f))) + 330
End Select
h = hue

h = h Mod 360

Dim As Single h1 = h / 60
Dim As Integer i = Int(h1)
Dim As Single f = h1 - i
Dim As Integer p = v * (255 - s) / 256
Dim As Integer q = v * (255 - f * s) / 256
Dim As Integer t = v * (255 - (1 - f) * s) / 256

Select Case As Const i
Case 0
r = v
g = t
b = p
Return
Case 1
r = q
g = v
b = p
Return
Case 2
r = p
g = v
b = t
Return
Case 3
r = p
g = q
b = v
Return
Case 4
r = t
g = p
b = v
Return
Case 5
r = v
g = p
b = q
Return
End Select
End Sub

Const pi As Single = 4 * Atn(1)
Const xres = (radius * 2) + 1, yres = xres

Screenres xres, yres, 32
Windowtitle "Color wheel"

Dim As Integer r,g,b
Dim As Single dx, dy, dist, angle

Do
Screenlock
Cls
For x As Integer = 0 To (radius * 2) - 1
For y As Integer = 0 To (radius * 2) - 1
dist = Sqr(dx * dx + dy * dy)
angle = Atan2(dy, dx) * (180/pi)
If angle <   0 Then angle += 360
If angle > 360 Then angle -= 360
HSVtoRGB(angle, (dist / radius) * 255, 255, r, g, b)
Pset(x, y), Rgb(r, g, b)
End If
Next y
Next x

Screenunlock
Loop Until Inkey = Chr(27)```

## FutureBasic

FB has native functions for programmatically building color wheels.

```_window = 1
begin enum output 1
_colorwheelImageView
end enum

void local fn BuildWindow
CGRect  r = fn CGRectMake( 0, 0, 400, 400 )

r = fn CGRectMake( 20, 20, 360, 360 )
imageview _colorwheelImageView, YES, , r, NSImageScaleProportionallyUpOrDown, NSImageAlignCenter, NSImageFrameNone, _window
end fn

local fn CIImageToImageRef( ciImage as CIImageRef ) as ImageRef
CIImageRepRef rep = fn CIImageRepWithCIImage( ciImage )
CGSize       size = fn ImageRepSize( rep )
ImageRef    image = fn ImageWithSize( size )
end fn = image

local fn ColorWheelImage( colorSpace as CGColorSpaceRef, dither as CFNumberRef, radius as CFNumberRef, softness as CFNumberRef, lightness as CFNumberRef ) as CIImageRef
CIFilterRef filter = fn CIFilterWithName( @"CIHueSaturationValueGradient" )
ObjectSetValueForkey( filter, colorSpace, @"inputColorSpace" )
ObjectSetValueForkey( filter, dither,     @"inputDither"     )
ObjectSetValueForkey( filter, softness,   @"inputSoftness"   )
ObjectSetValueForkey( filter, lightness,  @"inputValue"      )
CIImageRef outputCIImage = fn CIFilterOutputImage( filter )
end fn = outputCIImage

local fn BuildColorWheel
CIImageRef colorWheelCIImage = fn ColorWheelImage( fn CGColorSpaceCreateDeviceRGB, @0, @160, @0, @1 )
ImageRef   colorWheelImage   = fn CIImageToImageRef( colorWheelCIImage )
ImageViewSetImage( _colorwheelImageView, colorWheelImage )
end fn

fn BuildWindow
fn BuildColorWheel

HandleEvents```
Output:

## GML

```
for (var i = 1; i <= 360; i++) {
for (var j = 0; j < 255; j++) {

var hue = 255*(i/360);
var saturation = j;
var value = 255;

var c = make_colour_hsv(hue,saturation,value);

//size of circle determined by how far from the center it is
//if you just draw them too small the circle won't be full.
//it will have patches inside it that didn't get filled in with color
var r = max(1,3*(j/255));

//Math for built-in GMS functions
}
}```

## Go

Library: Go Graphics
Translation of: Kotlin
```package main

import (
"github.com/fogleman/gg"
"math"
)

const tau = 2 * math.Pi

func hsb2rgb(hue, sat, bri float64) (r, g, b int) {
u := int(bri*255 + 0.5)
if sat == 0 {
r, g, b = u, u, u
} else {
h := (hue - math.Floor(hue)) * 6
f := h - math.Floor(h)
p := int(bri*(1-sat)*255 + 0.5)
q := int(bri*(1-sat*f)*255 + 0.5)
t := int(bri*(1-sat*(1-f))*255 + 0.5)
switch int(h) {
case 0:
r, g, b = u, t, p
case 1:
r, g, b = q, u, p
case 2:
r, g, b = p, u, t
case 3:
r, g, b = p, q, u
case 4:
r, g, b = t, p, u
case 5:
r, g, b = u, p, q
}
}
return
}

func colorWheel(dc *gg.Context) {
width, height := dc.Width(), dc.Height()
centerX, centerY := width/2, height/2
}
for y := 0; y < height; y++ {
dy := float64(y - centerY)
for x := 0; x < width; x++ {
dx := float64(x - centerX)
dist := math.Sqrt(dx*dx + dy*dy)
theta := math.Atan2(dy, dx)
hue := (theta + math.Pi) / tau
r, g, b := hsb2rgb(hue, 1, 1)
dc.SetRGB255(r, g, b)
dc.SetPixel(x, y)
}
}
}
}

func main() {
const width, height = 480, 480
dc := gg.NewContext(width, height)
dc.SetRGB(1, 1, 1) // set background color to white
dc.Clear()
colorWheel(dc)
dc.SavePNG("color_wheel.png")
}
```
Output:
```Image is same as Kotlin entry
```

## J

```rgbc=: {{1-x*0>.1<.(<.4&-)6|m+y%60}}
hsv=: 5 rgbc(,"0 1) 3 rgbc(,"0) 1 rgbc
degrees=: {{180p_1*{:"1+.^.y}}
wheel=: {{((1>:|)*|hsv degrees)j./~y%~i:y}}
require'viewmat'
'rgb' viewmat 256#.<.255*wheel 400
```

The right argument to wheel determines the radius (in pixels) of the color wheel (with a white pixel in the center), so the diameter of the above color wheel is 801 pixels.

Here's a representation of wheel 5:

Here's an online implementation for wheel 80 (hit "Run" in the upper right corner).

## Java

This program draws a color wheel in a window.

```import java.awt.*;
import javax.swing.*;

public class ColorWheel {
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
ColorWheelFrame frame = new ColorWheelFrame();
frame.setVisible(true);
}
});
}

private static class ColorWheelFrame extends JFrame {
private ColorWheelFrame() {
super("Color Wheel");
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
pack();
}
}

private static class ColorWheelPanel extends JComponent {
private ColorWheelPanel() {
setPreferredSize(new Dimension(400, 400));
}
public void paint(Graphics g) {
Graphics2D g2 = (Graphics2D)g;
int w = getWidth();
int h = getHeight();
int margin = 10;
int radius = (Math.min(w, h) - 2 * margin)/2;
int cx = w/2;
int cy = h/2;
float[] dist = {0.F, 1.0F};
g2.setColor(Color.BLACK);
g2.fillRect(0, 0, w, h);
for (int angle = 0; angle < 360; ++angle) {
Color color = hsvToRgb(angle, 1.0, 1.0);
Color[] colors = {Color.WHITE, color};
g2.setPaint(paint);
angle, 1);
}
}
}

private static Color hsvToRgb(int h, double s, double v) {
double hp = h/60.0;
double c = s * v;
double x = c * (1 - Math.abs(hp % 2.0 - 1));
double m = v - c;
double r = 0, g = 0, b = 0;
if (hp <= 1) {
r = c;
g = x;
} else if (hp <= 2) {
r = x;
g = c;
} else if (hp <= 3) {
g = c;
b = x;
} else if (hp <= 4) {
g = x;
b = c;
} else if (hp <= 5) {
r = x;
b = c;
} else {
r = c;
b = x;
}
r += m;
g += m;
b += m;
return new Color((int)(r * 255), (int)(g * 255), (int)(b * 255));
}
}
```
Output:

## Julia

```using Gtk, Graphics, Colors

const win = GtkWindow("Color Wheel", 450, 450) |> (const can = @GtkCanvas())
set_gtk_property!(can, :expand, true)

@guarded draw(can) do widget
ctx = getgc(can)
h = height(can)
w = width(can)
center = (x = w / 2, y = h / 2)
anglestep = 1/w
for θ in 0:0.1:360
rgb = RGB(HSV(θ, 1, 1))
set_source_rgb(ctx, rgb.r, rgb.g, rgb.b)
line_to(ctx, center...)
arc(ctx, center.x, center.y, w/2.2, 2π * θ / 360, anglestep)
line_to(ctx, center...)
stroke(ctx)
end
end

show(can)
const condition = Condition()
endit(w) = notify(condition)
signal_connect(endit, win, :destroy)
wait(condition)
```

## Kotlin

We reuse the class in the Bitmap task for this and add a member function to draw the color wheel. To give a more 'wheel-like' image, a constant 'saturation' of 1.0 has been used rather than one which varies in line with distance from the center.

```// Version 1.2.41

import java.awt.Color
import java.awt.Graphics
import java.awt.image.BufferedImage
import java.io.File
import javax.imageio.ImageIO
import kotlin.math.*

class BasicBitmapStorage(width: Int, height: Int) {
val image = BufferedImage(width, height, BufferedImage.TYPE_3BYTE_BGR)

fun fill(c: Color) {
val g = image.graphics
g.color = c
g.fillRect(0, 0, image.width, image.height)
}

fun setPixel(x: Int, y: Int, c: Color) = image.setRGB(x, y, c.getRGB())

fun getPixel(x: Int, y: Int) = Color(image.getRGB(x, y))

fun colorWheel() {
val centerX = image.width / 2
val centerY = image.height / 2
for (y in 0 until image.height) {
val dy = (y - centerY).toDouble()
for (x in 0 until image.width) {
val dx = (x - centerX).toDouble()
val dist = sqrt(dx * dx + dy * dy)
val theta = atan2(dy, dx)
val hue = (theta + PI) / (2.0 * PI)
val rgb = Color.HSBtoRGB(hue.toFloat(), 1.0f, 1.0f)
setPixel(x, y, Color(rgb))
}
}
}
}
}

fun main(args: Array<String>) {
val bbs = BasicBitmapStorage(480, 480)
with (bbs) {
fill(Color.white)
colorWheel()
val cwFile = File("Color_wheel.png")
ImageIO.write(image, "png", cwFile)
}
}
```
Output:
```Looks like mirror image of Smart BASIC entry
```

## Lua

Library: LÖVE
```local function hsv_to_rgb (h, s, v)  -- values in ranges: [0, 360], [0, 1], [0, 1]
local r = math.min (math.max (3*math.abs (((h       )/180)%2-1)-1, 0), 1)
local g = math.min (math.max (3*math.abs (((h   -120)/180)%2-1)-1, 0), 1)
local b = math.min (math.max (3*math.abs (((h   +120)/180)%2-1)-1, 0), 1)
local k1 = v*(1-s)
local k2 = v - k1
return k1+k2*r, k1+k2*g, k1+k2*b -- values in ranges: [0, 1], [0, 1], [0, 1]
end

local w, h, r = 256, 256, 128-0.5
local cx, cy = w/2, h/2
canvas = love.graphics.newCanvas ()
love.graphics.setCanvas(canvas)
for x = 0, w do
for y = 0, h do
local dx, dy = x-cx, y-cy
if dx*dx + dy*dy <= r*r then
local h = math.deg(math.atan2(dy, dx))
local s = (dx*dx + dy*dy)^0.5/r
local v = 1
love.graphics.setColor (hsv_to_rgb (h, s, v))
love.graphics.points (x, y)
end
end
end
love.graphics.setCanvas()
end

function love.draw()
love.graphics.setColor (1,1,1)
love.graphics.draw (canvas)
end
```

## M2000 Interpreter

```Module Check {
\\ we use an internal object for Math functions (here for Atan2)
Declare Math Math
Const tau=2*Pi, Center=2
\\ change console size,  and center it ( using ;) to current monitor
Window 12, 800*twipsX,600*twipsY;
\\ actual size maybe less (so can fit text exactly)
Double  ' Double height characters
Report Center, "Color wheel"
Normal  ' restore to normal
Atan2=Lambda Math (a, b) ->{
Method Math, "Atan2", a, b As ret
=ret
}
\\ brightness=1 for this program
hsb2rgb=Lambda (hue, sat) ->{
If sat == 0 Then {
= 255, 255, 255
} Else {
h=frac(hue+1)*6
f = frac(h)
p = Int((1-sat)*255 + 0.5)
q = Int((1-sat*f)*255 + 0.5)
t = Int((1-sat*(1-f))*255 + 0.5)
Select Case Int(h)
Case 1
= q, 255, p
Case 2
= p, 255, t
Case 3
= p, q, 255
Case 4
= t, p, 255
Case 5
= 255, p, q
Else Case
= 255, t, p
End Select
}
}
Let OffsetX=X.twips/2-128*TwipsX, OffsetY=Y.twips/2-128*TwipsY
\\ a pixel has a size of TwipsX x TwipsY
OffsetX=(OffsetX div TwipsX)*TwipsX
OffsetY=(OffsetY div TwipsY)*TwipsY
\\ We set hsb2rgb, OffsetX, OffsetY as closures to PrintPixel
\\ We send to stack the R G B values using Stack ! array
\\ hsb2rgb() return an array of values
\\ we pop these values using Number
PrintPixel = Lambda  hsb2rgb, OffsetX, OffsetY (x,y, theta, sat)  -> {
Stack ! hsb2rgb(theta,sat)
PSet Color(number, number, number), x*TwipsX+offsetX, y*TwipsY+offsetY
}
\\ set Atan2, tau as closures to HueCircle
\\ we can rotate/flip the wheel by changing signs in Atan2() and
\\ by changing order of arguments (dx,dy) or (dy,dx). 8 combinations
HueCircle= Lambda Atan2, tau (PrintPixel) -> {
Let  c_width=256, c_height=256
Let  cx=c_width/2, cy=c_height/2
c_width--
c_height--
dy=-cy
For y=0 To c_height {
dy++ : dy2=dy*dy : dx=-cx
For x=0 To c_width {
dx++ : dist=Sqrt(dx^2+dy2)
}
}
}
Call HueCircle(PrintPixel)
Scr\$=""  ' we use this string  to load an image
Move 0,0
\\ scale.x, scale.y are twips height and width, of current layer
Copy scale.x, scale.y to Scr\$
Clipboard Scr\$  ' save window to clipboard
}
Check```
Output:

see this image

## Mathematica/Wolfram Language

```r = 100;
Image[Table[
If[x^2 + y^2 <= r^2,
angle = Mod[ArcTan[N@x, y]/(2 Pi), 1];
List @@ RGBColor[Hue[angle, Sqrt[x^2 + y^2]/N[r], 1.0]]
,
{1, 1, 1}
], {x, -r, r}, {y, -r, r}]
]
```
Output:

Outputs an image.

## Nim

Translation of: Rust
Library: imageman

As Rust code does, we store the color wheel in a PNG image.

```import math

import imageman

#---------------------------------------------------------------------------------------------------

func hsvToRgb(h, s, v: float): ColorRGBU =
## Convert HSV values to RGB values.

let hp = h / 60
let c = s * v
let x = c * (1 - abs(hp mod 2 - 1))
let m = v - c
var r, g, b = 0.0
if hp <= 1:
r = c
g = x
elif hp <= 2:
r = x
g = c
elif hp <= 3:
g = c
b = x
elif hp <= 4:
g = x
b= c
elif hp <= 5:
r = x
b = c
else:
r = c
b = x
r += m
g += m
b += m
result = ColorRGBU [byte(r * 255), byte(g * 255), byte(b * 255)]

#---------------------------------------------------------------------------------------------------

func buildColorWheel(image: var Image) =
## Build a color wheel into the image.

const Margin = 10
let diameter = min(image.w, image.h) - 2 * Margin
let xOffset = (image.w - diameter) div 2
let yOffset = (image.h - diameter) div 2
let radius = diameter / 2

for x in 0..diameter:
let rx = x.toFloat - radius
for y in 0..diameter:
let ry = y.toFloat - radius
let r = hypot(rx, ry) / radius
if r > 1: continue
let a = 180 + arctan2(ry, -rx).radToDeg()
image[x + xOffset, y + yOffset] = hsvToRgb(a, r, 1)

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

const
Side = 400
Output = "color_wheel.png"

var image = initImage[ColorRGBU](Side, Side)
image.buildColorWheel()

image.savePNG(Output, compression = 9)
```

## Perl

Translation of: Sidef
```use Imager;
use Math::Complex qw(cplx i pi);

my (\$width, \$height) = (300, 300);
my \$center = cplx(\$width/2, \$height/2);

my \$img = Imager->new(xsize => \$width,
ysize => \$height);

foreach my \$y (0 .. \$height - 1) {
foreach my \$x (0 .. \$width - 1) {

my \$vec = \$center - \$x - \$y * i;
my \$mag = 2 * abs(\$vec) / \$width;
my \$dir = (pi + atan2(\$vec->Re, \$vec->Im)) / (2 * pi);

\$img->setpixel(x => \$x, y => \$y,
color => {hsv => [360 * \$dir, \$mag, \$mag < 1 ? 1 : 0]});
}
}

\$img->write(file => 'color_wheel.png');
```

## Phix

Library: Phix/pGUI
Library: Phix/online

You can run this online here.

```--
-- demo\rosetta\Colour_wheel.exw
-- =============================
--
--  Note: Made non-resizeable since maximising this is far too slow.
--
with javascript_semantics
include pGUI.e

constant title = "Colour wheel"
Ihandle dlg, canvas
cdCanvas cddbuffer, cdcanvas

function redraw_cb(Ihandle /*ih*/, integer /*posx*/, /*posy*/)
integer {w, h} = IupGetIntInt(canvas, "DRAWSIZE")
cdCanvasActivate(cddbuffer)
integer cx = floor(w/2),
cy = floor(h/2)

for x=1 to w do
for y=1 to h do
integer rx = x - cx,
ry = y - cy
atom s = sqrt(rx*rx+ry*ry) / radius
if s <= 1.0 then
atom hue = ((atan2(ry, rx) / PI) + 1.0) / 2.0
cdCanvasPixel(cddbuffer, x, h-y, hsv_to_rgb(hue, s, 1))
end if
end for
end for
cdCanvasFlush(cddbuffer)
return IUP_DEFAULT
end function

function map_cb(Ihandle ih)
cdcanvas = cdCreateCanvas(CD_IUP, ih)
cddbuffer = cdCreateCanvas(CD_DBUFFER, cdcanvas)
cdCanvasSetBackground(cddbuffer, CD_WHITE)
cdCanvasSetForeground(cddbuffer, CD_MAGENTA)
return IUP_DEFAULT
end function

procedure main()
IupOpen()
canvas = IupCanvas(NULL)
IupSetAttribute(canvas, "RASTERSIZE", "300x300")
IupSetCallback(canvas, "MAP_CB", Icallback("map_cb"))
dlg = IupDialog(canvas,`TITLE="%s",RESIZE=NO`,{title})
IupSetCallback(canvas, "ACTION", Icallback("redraw_cb"))
IupShowXY(dlg,IUP_CENTER,IUP_CENTER)
if platform()!=JS then
IupMainLoop()
IupClose()
end if
end procedure

main()
```

## Processing

```size(300, 300);
background(0);
float radius = min(width, height) / 2.0;
float cx = width / 2;
float cy = width / 2;
for (int x = 0; x < width; x++) {
for (int y = 0; y < width; y++) {
float rx = x - cx;
float ry = y - cy;
float s = sqrt(sq(rx) + sq(ry)) / radius;
if (s <= 1.0) {
float h = ((atan2(ry, rx) / PI) + 1.0) / 2.0;
colorMode(HSB);
color c = color(int(h * 255), int(s * 255), 255);
set(x, y, c);
}
}
}
```

### Processing Python mode

```size(300, 300)
background(0)
radius = min(width, height) / 2.0
cx, cy = width / 2, width / 2
for x in range(width):
for y in range(height):
rx = x - cx
ry = y - cy
s = sqrt(rx ** 2 + ry ** 2) / radius
if s <= 1.0:
h = ((atan2(ry, rx) / PI) + 1.0) / 2.0
colorMode(HSB)
c = color(int(h * 255), int(s * 255), 255)
set(x, y, c) # note set() used as Processing set() not as Python set()
```

## Plain English

```To draw the color wheel:
Turn right 80 points.
Loop.
If the user clicks on the screen, break.
Move to the center of the screen.
Draw a line 2 inches long.
Refresh the screen.
Change the current hue by 10 points.
Turn right 10 points.
If the count is 384, break. \ Plain English uses a circle divided into 384 degrees
Repeat.
Start in the middle of the screen facing north minus 80 points.
Use medium-sized letters.
Write "RED......YELLOW.....GREEN......CYAN......BLUE.....MAGENTA......" with the white pen 2-1/4 inches from the screen's center.
Refresh the screen.
Shut down.```

## Python

```from PIL import Image
import colorsys
import math

if __name__ == "__main__":

im = Image.new("RGB", (300,300))
cx, cy = im.size[0]/2, im.size[1]/2

for x in range(im.width):
for y in range(im.height):
rx = x - cx
ry = y - cy
s = (rx ** 2.0 + ry ** 2.0) ** 0.5 / radius
if s <= 1.0:
h = ((math.atan2(ry, rx) / math.pi) + 1.0) / 2.0
rgb = colorsys.hsv_to_rgb(h, s, 1.0)
pix[x,y] = tuple([int(round(c*255.0)) for c in rgb])

im.show()
```

## Racket

With the colors package

```#lang racket

(require racket/draw
colors)

(define DIM 500)
(define target (make-bitmap DIM DIM))
(define dc (new bitmap-dc% [bitmap target]))
(define center (/ DIM 2))

(define (atan2 y x) (if (= 0 y x) 0 (atan y x)))

(for* ([x (in-range DIM)]
[y (in-range DIM)]
[rx (in-value (- x center))]
[ry (in-value (- y center))]
[s (in-value (/ (sqrt (+ (sqr rx) (sqr ry))) radius))]
#:when (<= s 1))
(define h (* 0.5 (+ 1 (/ (atan2 ry rx) pi))))
(send dc set-pen (hsv->color (hsv (if (= 1 h) 0 h) s 1)) 1 'solid)
(send dc draw-point x y))

target
```

## Raku

(formerly Perl 6)

Works with: Rakudo version 2016.08
```use Image::PNG::Portable;

my (\$w, \$h) = 300, 300;

my \$out = Image::PNG::Portable.new: :width(\$w), :height(\$h);

my \$center = \$w/2 + \$h/2*i;

color-wheel(\$out);

\$out.write: 'Color-wheel-perl6.png';

sub color-wheel ( \$png ) {
^\$w .race.map: -> \$x {
for ^\$h -> \$y {
my \$vector    = \$center - \$x - \$y*i;
my \$magnitude = \$vector.abs * 2 / \$w;
my \$direction = ( π + atan2( |\$vector.reals ) ) / τ;
\$png.set: \$x, \$y, |hsv2rgb( \$direction, \$magnitude, \$magnitude < 1 );
}
}
}

sub hsv2rgb ( \$h, \$s, \$v ){
my \$c = \$v * \$s;
my \$x = \$c * (1 - abs( ((\$h*6) % 2) - 1 ) );
my \$m = \$v - \$c;
(do given \$h {
when   0..^1/6 { \$c, \$x, 0 }
when 1/6..^1/3 { \$x, \$c, 0 }
when 1/3..^1/2 { 0, \$c, \$x }
when 1/2..^2/3 { 0, \$x, \$c }
when 2/3..^5/6 { \$x, 0, \$c }
when 5/6..1    { \$c, 0, \$x }
} ).map: ((*+\$m) * 255).Int
}
```

## Ring

```#===================================================================#
#  Sample: Color Wheel
#  Author: Gal Zsolt, Bert Mariani, Ilir Liburn & Mahmoud Fayed
#===================================================================#

xWidth  = 400
yHeight = 400

MyApp = new qapp
{
win1 = new qwidget()
{  setwindowtitle("ColorWheel-FastDraw")
setgeometry(500,150,xWidth,yHeight)

Canvas = new qlabel(win1)
{  ### daVinci paints the MonaLisa on the Canvas
MonaLisa  = new qPixMap2( xWidth, yHeight)
color = new qcolor(){ setrgb(255,255,255,0) }
pen  = new qpen()  { setwidth(1) }
MonaLisa.fill(color)

daVinci = new qpainter()
{  begin(MonaLisa)
#endpaint()           ### This will Stop the Painting. For Animation comment it out
}

setPixMap(MonaLisa)
}

show()
}

ColorWheel()
exec()
}

//=====================

Func colorWheel

#=====================================================================#
? "Start Processing..."
t1 = clock()
? "Clock : " + t1
#=====================================================================#

aList = []
pi       = 3.14159265359
diameter = pi * 2
v        = 1                    // value/brightness  1 to 100  1=bright 0=dark

for i = 1 to xWidth

for j = 1 to yHeight

h = (atan2( iradius, j-radius ) + pi ) / diameter   // hue/color  1 to 360
s =   sqrt( p + pow( j-radius, 2)) / radius         // saturation/intensity 1 to 100

if s <= 1 and h <= 1
aList + [i,j,h,s,v,1]
ok

next
next

#=====================================================================#
? "Start drawing..."
t2 = clock()
? "Clock : " + t2
#=====================================================================#

daVinci.drawHSVFList(aList)
Canvas.setPixMap(MonaLisa)

#=====================================================================#
? "Done..."
t3 = clock()
? "Clock : " + t3
#=====================================================================#
? "Processing Time: " + ( (t2-t1)/ClocksPerSecond() ) + " seconds "
? "Drawing Time: " + ( (t3-t2)/ClocksPerSecond() ) + " seconds "
? "Total Time: " + ( (t3-t1)/ClocksPerSecond() ) + " seconds "
#=====================================================================#

return

//==================```

## Ruby

Library: RubyGems
Library: JRubyArt
```def settings
size(300, 300)
end

def setup
sketch_title 'Color Wheel'
background(0)
center = width / 2
grid(width, height) do |x, y|
rx = x - center
ry = y - center
sat = Math.hypot(rx, ry) / radius
if sat <= 1.0
hue = ((Math.atan2(ry, rx) / PI) + 1) / 2.0
color_mode(HSB)
col = color((hue * 255).to_i, (sat * 255).to_i, 255)
set(x, y, col)
end
end
end
```

## Run BASIC

```' -----------------------------------
' color wheel
' -----------------------------------
global pi
pi  = 22 / 7
steps   = 1

graphic #g, 525, 525

for x =0 to 525 step steps
for y =0 to 525 step steps
angle   = atan2(y - 250, x - 250) * 360 / 2 / pi      '  full degrees....
sector  = int(angle / 60)                             '    60 degree sectors (0 to 5)
slope   = (angle mod 60) /60 * 255                    '     1 degree sectors.

if  sector = 0 then  col\$    = "255 ";                    str\$( int( slope));      "   0"
if  sector = 1 then  col\$    = str\$(int(256 - slope)); " 255                          0"
if  sector = 2 then  col\$    = "0                         255 ";                     str\$( int( slope))
if  sector = 3 then  col\$    = "0 ";                      str\$( int( 256 -slope)); " 255"
if  sector = 4 then  col\$    = str\$(int(slope));    "     0                        255"
if  sector = 5 then  col\$    = "255                         0 ";                     str\$( int( 256 -slope))

red = val( word\$( col\$, 1))
grn = val( word\$( col\$, 2))
blu = val( word\$( col\$, 3))
p   = ((x -270)^2 +(y -270)^2)^0.5 / 250
r   = min(255,p * red)
g   = min(255,p * grn)
b   = min(255,p * blu)
if p > 1 then  #g "color white" else #g color(r,g,b)
#g "set "; x; " "; y
next y
next x
render #g
end

function atan2(y,x)
if (x = 0) and (y <> 0) then
r\$ = "Y"
if y > 0 then atan2 = pi /2
if y < 0 then atan2 = 3 * pi /2
end if

if y = 0 and (x <> 0) then
r\$ = "Y"
if x > 0 then atan2 = 0
if x < 0 then atan2 = pi
end if

If r\$ <> "Y" then
if x = 0 and y = 0 then
atan2   = 0
else
baseAngle = atn(abs(y) / abs(x))
if x > 0 then
if y > 0 then atan2 = baseAngle
If y < 0 then atan2 = 2 * pi - baseAngle
end if
if x < 0 then
If y > 0 then atan2 = pi - baseAngle
If y < 0 then atan2 = pi + baseAngle
end if
end if
end if
end function```

## Rust

Output is a file in PNG format.

```// [dependencies]
// image = "0.23"

use image::error::ImageResult;
use image::{Rgb, RgbImage};

fn hsv_to_rgb(h: f64, s: f64, v: f64) -> Rgb<u8> {
let hp = h / 60.0;
let c = s * v;
let x = c * (1.0 - (hp % 2.0 - 1.0).abs());
let m = v - c;
let mut r = 0.0;
let mut g = 0.0;
let mut b = 0.0;
if hp <= 1.0 {
r = c;
g = x;
} else if hp <= 2.0 {
r = x;
g = c;
} else if hp <= 3.0 {
g = c;
b = x;
} else if hp <= 4.0 {
g = x;
b = c;
} else if hp <= 5.0 {
r = x;
b = c;
} else {
r = c;
b = x;
}
r += m;
g += m;
b += m;
Rgb([(r * 255.0) as u8, (g * 255.0) as u8, (b * 255.0) as u8])
}

fn write_color_wheel(filename: &str, width: u32, height: u32) -> ImageResult<()> {
let mut image = RgbImage::new(width, height);
let margin = 10;
let diameter = std::cmp::min(width, height) - 2 * margin;
let xoffset = (width - diameter) / 2;
let yoffset = (height - diameter) / 2;
let radius = diameter as f64 / 2.0;
for x in 0..=diameter {
let rx = x as f64 - radius;
for y in 0..=diameter {
let ry = y as f64 - radius;
let r = ry.hypot(rx) / radius;
if r > 1.0 {
continue;
}
let a = 180.0 + ry.atan2(-rx).to_degrees();
image.put_pixel(x + xoffset, y + yoffset, hsv_to_rgb(a, r, 1.0));
}
}
image.save(filename)
}

fn main() {
match write_color_wheel("color_wheel.png", 400, 400) {
Ok(()) => {}
Err(error) => eprintln!("{}", error),
}
}
```
Output:

## Sidef

Translation of: Raku
```require('Imager')

var (width, height) = (300, 300)
var center = Complex(width/2 , height/2)

var img = %O<Imager>.new(xsize => width, ysize => height)

for y=(^height), x=(^width) {
var vector    = (center - x - y.i)
var magnitude = (vector.abs * 2 / width)
var direction = ((Num.pi + atan2(vector.real, vector.imag)) / Num.tau)
img.setpixel(x => x, y => y,
color => Hash(hsv => [360*direction, magnitude, magnitude < 1 ? 1 : 0])
)
}

img.write(file => 'color_wheel.png')
```

Output image: Color wheel

## Smart BASIC

```' Runs on iOS
GET SCREEN SIZE sw,sh
xmax=0.45*3/7*(sw+sh)
x0=sw/2!y0=sh/2
twopi=2*3.1415926
GRAPHICS
GRAPHICS CLEAR
DIM triX(1000), triY(1000)
triX(0)=x0 ! triY(0)=y0
steps=INT(1^2*360)+1
dAngle=twopi/steps
dAngle2=dAngle/2
REFRESH OFF
FOR i=0 TO steps-1
pal(i/steps+TintOffset)
ANGLE=i*dAngle
FILL COLOR pal.r,pal.g,pal.b
DRAW COLOR pal.r,pal.g,pal.b
k=0
FOR j=-dAngle2 TO dAngle2 STEP 0.02
k+=1
triX(k)=x0+xmax*COS(ANGLE+j)
triY(k)=y0-xmax*SIN(ANGLE+j)
NEXT j
k+=1
triX(k)=x0+xmax*COS(ANGLE+dAngle2)
triY(k)=y0-xmax*SIN(ANGLE+dAngle2)
DRAW POLY triX,triY COUNT k+1
FILL POLY triX,triY COUNT k+1
NEXT i
REFRESH ON
END

DEF pal(tint)
tint=tint*360
h=(tint%360)/60 ! f=FRACT(h) ! z=1-f ! ic=FLOOR(h)+1
ON ic GOTO s1,s2,s3,s4,s5,s6
s1: r=1 ! g=f ! b=0 ! GOTO done
s2: r=z ! g=1 ! b=0 ! GOTO done
s3: r=0 ! g=1 ! b=f ! GOTO done
s4: r=0 ! g=z ! b=1 ! GOTO done
s5: r=f ! g=0 ! b=1 ! GOTO done
s6: r=1 ! g=0 ! b=z ! done:
END DEF```

View the output on Dropbox https://www.dropbox.com/s/g3l5rbywo34bnp6/IMG_4600.PNG?dl=0 This file is no longer there!!! 10 Sep 2021

## Vala

Translation of: Julia
```public class Example: Gtk.Application {
private Gtk.ApplicationWindow window;
private Gtk.DrawingArea drawing_area;
public Example() {
Object(application_id: "my.application", flags: ApplicationFlags.FLAGS_NONE);
this.activate.connect(() => {
window = new Gtk.ApplicationWindow(this);
drawing_area = new Gtk.DrawingArea();
drawing_area.set_draw_func(draw_circle);
window.set_child(drawing_area);
window.present();
});
}

private void draw_circle(Gtk.DrawingArea area, Cairo.Context cr, int width, int height) {
int centerx = width / 2;
int centery = height / 2;
double anglestep = 1.0 / width;
for (float theta = (float) 0.0; theta < 360; theta += (float) 0.1) {
float r;
float g;
float b;
Gtk.hsv_to_rgb(theta / (float) 360.0, 1, 1, out r, out g, out b);
cr.set_source_rgb(r, g, b);
cr.line_to(centerx, centery);
cr.arc(centerx, centery, ((double) width) / 2.2, GLib.Math.PI * 2 * theta / 360.0, anglestep);
cr.line_to(centerx, centery);
cr.stroke();
}
}

public static int main(string[] argv) {
var app = new Example();
return app.run(argv);
}
}
```

## VBScript

Building a BMP file and opening it with the default viewer. It takes 5 seconds in my 5 years old notebook. Run with Cscript if you don want to be clicking at annoying message boxes.

```Option explicit

Class ImgClass
Private ImgL,ImgH,ImgDepth,bkclr,loc,tt
private xmini,xmaxi,ymini,ymaxi,dirx,diry
public ImgArray()  'rgb in 24 bit mode, indexes to palette in 8 bits
private filename
private Palette,szpal

public property get xmin():xmin=xmini:end property
public property get ymin():ymin=ymini:end property
public property get xmax():xmax=xmaxi:end property
public property get ymax():ymax=ymaxi:end property
public property let depth(x)
if x<>8 and x<>32 then err.raise 9
Imgdepth=x
end property

public sub set0 (x0,y0) 'sets the new origin (default tlc). The origin does'nt work if ImgArray is accessed directly
if x0<0 or x0>=imgl or y0<0 or y0>imgh then err.raise 9
xmini=-x0
ymini=-y0
xmaxi=xmini+imgl-1
ymaxi=ymini+imgh-1
end sub

'constructor
Public Default Function Init(name,w,h,orient,dep,bkg,mipal)
'offx, offy posicion de 0,0. si ofx+ , x se incrementa de izq a der, si offy+ y se incrementa de abajo arriba
dim i,j
ImgL=w
ImgH=h
tt=timer
loc=getlocale
' not useful as we are not using SetPixel and accessing  ImgArray directly
set0 0,0   'origin blc positive up and right
redim imgArray(ImgL-1,ImgH-1)
bkclr=bkg
if bkg<>0 then
for i=0 to ImgL-1
for j=0 to ImgH-1
imgarray(i,j)=bkg
next
next
end if
Select Case orient
Case 1: dirx=1 : diry=1
Case 2: dirx=-1 : diry=1
Case 3: dirx=-1 : diry=-1
Case 4: dirx=1 : diry=-1
End select
filename=name
ImgDepth =dep
if imgdepth=8 then
end if
set init=me
end function

if isarray(mipale) Then
palette=mipale
szpal=UBound(mipale)+1
Else
szpal=256
'Default palette recycled from ATARI
'removed

, not relevant
End if
End Sub

'class termination writes it to a BMP file and displays it
'if an error happens VBS terminates the class before exiting so the BMP is displayed the same
Private Sub Class_Terminate

if err<>0 then wscript.echo "Error " & err.number
wscript.echo "copying image to bmp file"
savebmp
wscript.echo "opening " & filename & " with your default bmp viewer"
CreateObject("Shell.Application").ShellExecute filename
wscript.echo timer-tt & "  iseconds"
End Sub

function long2wstr( x)  'falta muy poco!!!
dim k1,k2,x1
k1=  (x and &hffff&)' or (&H8000& And ((X And &h8000&)<>0)))
k2=((X And &h7fffffff&) \ &h10000&) Or (&H8000& And (x<0))
long2wstr=chrw(k1) & chrw(k2)
end function

function int2wstr(x)
int2wstr=ChrW((x and &h7fff) or (&H8000 And (X<0)))
End Function

Public Sub SaveBMP
'Save the picture to a bmp file
Dim s,ostream, x,y,loc

const hdrs=54 '14+40
dim bms:bms=ImgH* 4*(((ImgL*imgdepth\8)+3)\4)  'bitmap size including padding
dim palsize:if (imgdepth=8) then palsize=szpal*4 else palsize=0

with  CreateObject("ADODB.Stream") 'auxiliary ostream, it creates an UNICODE with bom stream in memory
.Charset = "UTF-16LE"    'o "UTF16-BE"
.open

'bmp header: VBSCript does'nt have records nor writes binary values to files, so we use strings of unicode chars!!
.writetext ChrW(&h4d42)                           ' 0 "BM" 4d42
.writetext long2wstr(hdrs+palsize+bms)            ' 2 fiesize
.writetext long2wstr(0)                           ' 6  reserved
.writetext long2wstr (hdrs+palsize)               '10 image offset
.writetext long2wstr(Imgl)                        '18 image length
.writetext long2wstr(imgh)                        '22 image width
.writetext int2wstr(1)                            '26 planes
.writetext int2wstr(imgdepth)                     '28 clr depth (bpp)
.writetext long2wstr(&H0)                         '30 compression used 0= NOCOMPR

.writetext long2wstr(bms)                         '34 imgsize
.writetext long2wstr(&Hc4e)                       '38 bpp hor
.writetext long2wstr(&hc43)                       '42 bpp vert
.writetext long2wstr(szpal)                       '46  colors in palette
.writetext long2wstr(&H0)                         '50 important clrs 0=all

'write bitmap
'precalc data for orientation
Dim x1,x2,y1,y2
If dirx=-1 Then x1=ImgL-1 :x2=0 Else x1=0:x2=ImgL-1
If diry=-1 Then y1=ImgH-1 :y2=0 Else y1=0:y2=ImgH-1

Select Case imgdepth

Case 32
For y=y1 To y2  step diry
For x=x1 To x2 Step dirx
'writelong fic, Pixel(x,y)
.writetext long2wstr(Imgarray(x,y))
Next
Next

Case 8
'palette
For x=0 to szpal-1
.writetext long2wstr(palette(x))  '52
Next
'image
For y=y1 to y2 step diry
For x=x1 To x2 step dirx*2
.writetext chrw((ImgArray(x,y) and 255)+ &h100& *(ImgArray(x+dirx,y) and 255))
Next
if pad and 1 then .writetext  chrw(ImgArray(x2,y))
if pad >1 then .writetext  chrw(0)
Next

Case Else
WScript.Echo "ColorDepth not supported : " & ImgDepth & " bits"
End Select

'use a second stream to save to file starting past the BOM  the first ADODB.Stream has added
outf.Open
.position=2              'remove bom (1 wchar)
.CopyTo outf
.close
outf.close
end with
End Sub
end class

function hsv2rgb( Hue, Sat, Value) 'hue 0-360   0-ro 120-ver 240-az ,sat 0-100,value 0-100
dim r,g,b, rgb
Angle = (Hue-150) *0.01745329251994329576923690768489
Ur = Value * 2.55
Radius = Ur * tan(Sat *0.01183199)
Vr = Radius * cos(Angle) *0.70710678  'sqrt(1/2)
Wr = Radius * sin(Angle) *0.40824829  'sqrt(1/6)
r = (Ur - Vr - Wr)
g = (Ur + Vr - Wr)
b = (Ur + Wr + Wr)

'clamp values
if r >255 then
Rdim = (Ur - 255) / (Vr + Wr)
r = 255
g = Ur + (Vr - Wr) * Rdim
b = Ur + 2 * Wr * Rdim
elseif r < 0 then
Rdim = Ur / (Vr + Wr)
r = 0
g = Ur + (Vr - Wr) * Rdim
b = Ur + 2 * Wr * Rdim
end if

if g >255 then
Rdim = (255 - Ur) / (Vr - Wr)
r = Ur - (Vr + Wr) * Rdim
g = 255
b = Ur + 2 * Wr * Rdim
elseif g<0 then
Rdim = -Ur / (Vr - Wr)
r = Ur - (Vr + Wr) * Rdim
g = 0
b = Ur + 2 * Wr * Rdim
end if
if b>255 then
Rdim = (255 - Ur) / (Wr + Wr)
r = Ur - (Vr + Wr) * Rdim
g = Ur + (Vr - Wr) * Rdim
b = 255
elseif b<0 then
Rdim = -Ur / (Wr + Wr)
r = Ur - (Vr + Wr) * Rdim
g = Ur + (Vr - Wr) * Rdim
b = 0
end If
'b lowest byte, red highest byte
hsv2rgb= ((b and &hff)+256*((g and &hff)+256*(r and &hff))and &hffffff)
end function

function ang(col,row)
'if col =0 then  if row>0 then ang=0 else ang=180:exit function
if col =0 then
if row<0 then ang=90 else ang=270 end if
else
if col>0 then
ang=atn(-row/col)*57.2957795130
else
ang=(atn(row/-col)*57.2957795130)+180
end if
end if
ang=(ang+360) mod 360
end function

Dim X,row,col,fn,tt,hr,sat,row2
const h=160
const w=160
const r2=25500
tt=timer
fn=CreateObject("Scripting.FileSystemObject").GetSpecialFolder(2)& "\testwchr.bmp"
Set X = (New ImgClass)(fn,w*2,h*2,1,32,0,0)

x.set0 w,h
'wscript.echo x.xmax, x.xmin

for row=x.xmin+1 to x.xmax
row2=row*row
hr=int(Sqr(r2-row2))
For col=hr To 159
Dim a:a=((col\16 +row\16) And 1)* &hffffff
x.imgArray(col+160,row+160)=a
x.imgArray(-col+160,row+160)=a
next
for col=-hr to hr
' wscript.echo c,r
x.imgArray(col+160,row+160)=hsv2rgb(ang(row,col)+90,100,sat)
next
'script.echo row
next
Set X = Nothing```

==

Output:

==

## Wren

Library: DOME
```import "graphics" for Canvas, Color
import "dome" for Window
import "random" for Random

class Game {
static init() {
Window.title = "Color Wheel"
__width = 640
__height = 640
Window.resize(__width, __height)
Canvas.resize(__width, __height)
colorWheel()
}

static colorWheel() {
var cx = (__width/2).floor
var cy = (__height/2).floor
var r = (cx < cy) ? cx : cy
for (y in 0...__height) {
var dy = y - cy
for (x in 0...__width) {
var dx = x - cx
var dist = (dx*dx + dy*dy).sqrt
if (dist <= r) {
var theta = dy.atan(dx)
var h = (theta + Num.pi) / Num.pi * 180
var col = Color.hsv(h, dist/r, 1)
Canvas.pset(x, y, col)
}
}
}
}

static update() {}

static draw(alpha) {}
}
```

## XPL0

Algorithm is from "Computer Graphics ..." by Foley et al. The output is the same as Zkl.

```def  Radius = 480/2;
real Hue, Sat, Dist, I, F, P, Q, T;
real XX, YY, RR, GG, BB;
int  X, Y, R, G, B;
def  Pi = 3.141592654;
def  V = 1.;            \Value
[SetVid(\$112);          \640x480x24 graphics
[XX:= float(X);
YY:= float(Y);
Dist:= sqrt(XX*XX + YY*YY);
[Sat:= Dist/float(Radius);      \0 >= Sat <= 1
Hue:= ATan2(YY, XX);            \-Pi >= Hue <= Pi
if Hue < 0. then Hue:= Hue + 2.*Pi;
Hue:= Hue * 180./Pi;            \radians to degrees
Hue:= Hue / 60.;                \0 >= Hue < 6
I:= Floor(Hue);                 \integer part of Hue
F:= Hue - I;                    \fractional part of Hue
P:= 1. - Sat;
Q:= 1. - Sat*F;
T:= 1. - Sat*(1.-F);
case fix(I) of
0:    [RR:= V;  GG:= T;  BB:= P];
1:    [RR:= Q;  GG:= V;  BB:= P];
2:    [RR:= P;  GG:= V;  BB:= T];
3:    [RR:= P;  GG:= Q;  BB:= V];
4:    [RR:= T;  GG:= P;  BB:= V];
5:    [RR:= V;  GG:= P;  BB:= Q]
other   [exit 1];
R:= fix(RR*255.);
G:= fix(GG*255.);
B:= fix(BB*255.);
];
];
]```

## zkl

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

```var w=300,h=300,out=PPM(w,h);
colorWheel(out);
out.writeJPGFile("colorWheel.zkl.jpg");

fcn colorWheel(ppm){
zero,R:=ppm.w/2, zero;
foreach x,y in (w,h){
v,hue:=(x - zero).toFloat().toPolar(y - zero);
if(v<=R){    // only render in the circle
if((hue = hue.toDeg())<0) hue+=360;  // (-pi..pi] to [0..2pi)
s:=v/R;  // scale saturation zero at center to 1 at edge
ppm[x,y]=hsv2rgb(hue,1.0,s);
}
}
}

fcn hsv2rgb(hue,v,s){  //  0<=H<360, 0<=v(brightness)<=1, 0<=saturation<=1
// --> 24 bit RGB each R,G,B in [0..255]
to24bit:=fcn(r,g,b,m){
r,g,b=((r+m)*255).toInt(),((g+m)*255).toInt(),((b+m)*255).toInt();
r*0x10000 + g*0x100 + b
};
c:=v*s;
x:=c*(1.0 - (hue.toFloat()/60%2 - 1).abs());
m:=v - c;
if     (0  <=hue< 60) return(to24bit(c,  x,  0.0,m));
else if(60 <=hue<120) return(to24bit(x,  c,  0.0,m));
else if(120<=hue<180) return(to24bit(0.0,c,  x,  m));
else if(180<=hue<240) return(to24bit(0.0,x,  c,  m));
else if(240<=hue<300) return(to24bit(x,  0.0,c,  m));
else          return(to24bit(c,  0.0,x,  m));
}```
Output:

See this image