Color wheel
Write a function to draw a HSV color wheel completely with code.
You are encouraged to solve this task according to the task description, using any language you may know.
- Task
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 120 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,SAppleScript
choose color default color {0, 0, 0, 0}
C++
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));
QRadialGradient gradient(center, diameter/2.0);
gradient.setColorAt(0, white);
gradient.setColorAt(1, color);
QBrush brush(gradient);
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:
Delphi
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;
Radius: Integer;
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;
Radius := Center.X;
if Center.Y < Radius then
Radius := Center.Y;
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));
if dist <= Radius then
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].
Fōrmulæ
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Programs in Fōrmulæ are created/edited online in its website, However they run on execution servers. By default remote servers are used, but they are limited in memory and processing power, since they are intended for demonstration and casual use. A local server can be downloaded and installed, it has no limitations (it runs in your own computer). Because of that, example programs can be fully visualized and edited, but some of them will not run if they require a moderate or heavy computation/memory resources, and no local server is being used.
In this page you can see the program(s) related to this task and their results.
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 radius = 160
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
dx = x - radius
dy = radius - y
dist = Sqr(dx * dx + dy * dy)
If dist < radius Then
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)
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
//lengthdir_x(len,dir) = +cos(degtorad(direction))*length;
//lengthdir_y(len,dir) = -sin(degtorad(direction))*length;
draw_circle_colour(x+lengthdir_x(m_radius*(j/255),i),y+lengthdir_y(m_radius*(j/255),i),r,c,c,false);
}
}Go
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
radius := centerX
if centerY < radius {
radius = centerY
}
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)
if dist <= float64(radius) {
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);
getContentPane().add(new ColorWheelPanel());
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};
RadialGradientPaint paint = new RadialGradientPaint(cx, cy,
radius, dist, colors);
g2.setPaint(paint);
g2.fillArc(cx - radius, cy - radius, radius*2, radius*2,
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
val radius = minOf(centerX, centerY)
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)
if (dist <= radius) {
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
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
function love.load()
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
Let radius=If(cx<=cy->cx, cy)
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)
If dist>radius Then continue
Call PrintPixel(x,y, Atan2(dx, -dy)/tau, dist/radius)
}
}
}
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
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
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
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 radius = floor(min(w,h)/2) 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()
Python
from PIL import Image
import colorsys
import math
if __name__ == "__main__":
im = Image.new("RGB", (300,300))
radius = min(im.size)/2.0
cx, cy = im.size[0]/2, im.size[1]/2
pix = im.load()
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 radius 200)
(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)
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
}
Until local image uploading is re-enabled, see Color-wheel-perl6.png
Ring
#===================================================================#
# Sample: Color Wheel
# Author: Gal Zsolt, Bert Mariani, Ilir Liburn & Mahmoud Fayed
#===================================================================#
load "guilib.ring"
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
radius = yHeight / 2
v = 1 // value/brightness 1 to 100 1=bright 0=dark
for i = 1 to xWidth
iradius = i - radius
p = pow( iradius, 2)
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
def settings
size(300, 300)
end
def setup
sketch_title 'Color Wheel'
background(0)
radius = width / 2.0
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 functionRust
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
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
x=x0+(xmax-radius)*COS(ANGLE)
y=y0-(xmax-radius)*SIN(ANGLE)
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 DEFView the output on Dropbox https://www.dropbox.com/s/g3l5rbywo34bnp6/IMG_4600.PNG?dl=0 This file is no longer there!!! 10 Sep 2021
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,nclr,tt
private xmini,xmaxi,ymini,ymaxi
dim ImgArray() 'rgb in 24 bit mode, indexes to palette in 8 bits
private filename
private Palette
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)
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,dep,bkg,pal)
dim i,j
ImgL=w
ImgH=h
tt=timer
depth=dep
if dep<>8 and dep <>32 then err.raise 9
set0 0,0 'tlc
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
filename=name
'load user palette if provided
if imgdepth=8 then
if isarray(pal) then
if ubound(pal)=255 then
palette=pal
else
mypalette
end if
else
mypalette
end if
end if
set init=me
end function
'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 uour default viewer"
CreateObject("Shell.Application").ShellExecute filename
wscript.echo timer-tt & " milliseconds"
End Sub
function long2str(byval k)
Dim s
s= chr(k and &hff)
k=k\&h100
s=s& chr(k and &hff)
k=k\&h100
s=s& chr(k and &hff)
k=k\&h100
s=s& chr(k and &hff)
long2str=s
End function
function int2str(byval k)
Dim s
s= chr(k and &hff)
k=k\&h100
s=s& chr(k and &hff)
int2str=s
End function
Public Sub SaveBMP
'Save the picture to a bmp file
Dim s,ostream, x,y,loc
dim bpp:bpp=imgdepth\8
const hdrs=54 '14+40
dim bms:bms=ImgH* 4*(((ImgL*bpp)+3)\4) 'bitmap size including padding
dim pals:if (imgdepth=8) then pals=(ubound(Palette)+1)*4 else pals=0
loc=getlocale
setlocale "us"
with CreateObject("ADODB.Stream") 'auxiliary ostream, it creates an UNICODE with bomb stream in memory
.Charset = "Windows-1252"
.Type = 2' adTypeText
.open
'build a header
'bmp header: VBSCript does'nt have records nor writes binary values to files, so we use strings of unicode chars!!
'BMP head 0 "BM" 'Type 2 size 6 10 14
.writetext "BM" & long2str(hdrs+pals+bms)& long2str(0) &long2str (hdrs+pals)
'InfoHeader 14 hdr sz 18 length 22 width 26 pla 28 clr depth 30 NOCOMPR 34
.writetext long2str(40) &long2str(Imgl)&long2str(imgh) & int2str(1) & int2str(imgdepth)& long2str(&H0)
' 34 nosize 38 bpp 42 bpp 46 cls pal 50 imp clrs 54
.writetext long2str(bms)&long2str(&Hc4e)& long2str(&hc43)& long2str(&H0) & long2str(&H0)
'add palette if exists
If (imgdepth=8) Then
s=""
For x=0 to ubound(palette)
s=s& long2str(palette(x))
Next
.writetext s
End If
'write bitmap
Select Case ImgDepth
Case 32
'wscript.echo imgdepth
For y=ImgH-1 to 0 step-1 'Origin of bitmap: bottom left
s=""
For x=0 To ImgL-1
'writelong fic, Pixel(x,y)
s=s & long2str(Imgarray(x,y))
Next
.writetext s
Next
Case 8
dim xx:xx=ImgL mod 4
For y=ImgH-1 to 0 step-1
s=""
For x=0 To ImgL-1 step 2
s=s & chrw((ImgArray(x,y) and 255 )+ 256*(ImgArray(x+1,y) and 255))
Next
if xx and 1 then s=s &chrw(ImgArray(Imgl-1,y))
if xx >1 then s=s & chrw(0)
.writetext s
Next
Case Else
WScript.Echo "ColorDepth not supported : " & ImgDepth & " bits"
End Select
'save to file
.position=0 'using single byte chars, no bom
.savetofile filename,2 'adSaveCreateOverWrite
.close
end with
setlocale loc
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 Angle, Radius,Ur,Vr,Wr,Rdim
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
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 rad=159
const r2=25500
tt=timer
fn=CreateObject("Scripting.FileSystemObject").GetSpecialFolder(2)& "\test.bmp"
Set X = (New ImgClass)(fn,w*2,h*2,32,0,0)
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 hr
sat=100-sqr(row2+col*col)/rad *50
' wscript.echo c,r
x.imgArray(col+160,row+160)=hsv2rgb(ang(row,col)+90,100,sat)
next
'script.echo row
next
Set X = NothingWren
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
for Y:= -Radius to Radius do
for X:= -Radius to Radius do
[XX:= float(X);
YY:= float(Y);
Dist:= sqrt(XX*XX + YY*YY);
if Dist <= float(Radius) then
[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.);
Point(X+Radius, Radius-Y, R<<16+G<<8+B);
];
];
]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
