--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/dwtx/jface/internal/text/revisions/Colors.d	Sat Aug 23 19:10:48 2008 +0200
@@ -0,0 +1,271 @@
+/*******************************************************************************
+ * Copyright (c) 2006, 2007 IBM Corporation and others.
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/legal/epl-v10.html
+ *
+ * Contributors:
+ *     IBM Corporation - initial API and implementation
+ * Port to the D programming language:
+ *     Frank Benoit <benoit@tionex.de>
+ *******************************************************************************/
+module dwtx.jface.internal.text.revisions.Colors;
+
+import dwt.dwthelper.utils;
+
+
+import dwt.DWT;
+import dwt.graphics.RGB;
+import dwtx.core.runtime.Assert;
+
+/**
+ * Utility for color operations.
+ * 
+ * @since 3.3
+ */
+public final class Colors {
+    /*
+     * Implementation note: Color computation assumes sRGB, which is probably not true, and does not
+     * always give good results. CIE based algorithms would be better, see
+     * http://www.w3.org/TR/PNG-ColorAppendix.html and http://en.wikipedia.org/wiki/Lab_color_space
+     */
+
+    /**
+     * Returns the human-perceived brightness of a color as float in [0.0, 1.0]. The used RGB
+     * weights come from http://www.poynton.com/notes/colour_and_gamma/ColorFAQ.html#RTFToC9.
+     * 
+     * @param rgb the color
+     * @return the gray-scale value
+     */
+    public static float brightness(RGB rgb) {
+        return Math.min(1f, (0.2126f * rgb.red + 0.7152f * rgb.green + 0.0722f * rgb.blue + 0.5f) / 255f);
+    }
+
+    /**
+     * Normalizes a color in its perceived brightness. Yellows are darkened, while blues and reds
+     * are lightened. Depending on the hue, the brightness range within the RGB gamut may be
+     * different, outside values are clipped. Note that this is an approximation; the returned RGB
+     * is not guaranteed to have the requested {@link #brightness(RGB) brightness}.
+     * 
+     * @param color the color to normalize
+     * @param brightness the requested brightness, in [0,&nbsp;1]
+     * @return a normalized version of <code>color</code>
+     * @see #brightness(RGB)
+     */
+    public static RGB adjustBrightness(RGB color, float brightness) {
+        float[] hsi= toHSI(color);
+        float psychoFactor= brightness - brightness(color);
+        float weight= 0.5f; // found by trial and error
+        hsi[2]= Math.max(0, Math.min(1.0f, hsi[2] + psychoFactor * weight));
+        color= fromHSI(hsi);
+        return color;
+    }
+
+    /**
+     * Converts an {@link RGB} to an <a href="http://en.wikipedia.org/wiki/HSL_color_space">HSI</a>
+     * triplet.
+     * 
+     * @param color the color to convert
+     * @return the HSI float array of length 3
+     */
+    private static float[] toHSI(RGB color) {
+        float r = color.red / 255f;
+        float g = color.green / 255f;
+        float b = color.blue / 255f;
+        float max = Math.max(Math.max(r, g), b);
+        float min = Math.min(Math.min(r, g), b);
+        float delta = max - min;
+        float maxPlusMin= max + min;
+        float intensity = maxPlusMin / 2;
+        float saturation= intensity < 0.5 ? delta / maxPlusMin : delta / (2 - maxPlusMin);
+
+        float hue = 0;
+        if (delta !is 0) {
+            if (r is max) {
+                hue = (g  - b) / delta;
+            } else {
+                if (g is max) {
+                    hue = 2 + (b - r) / delta;  
+                } else {
+                    hue = 4 + (r - g) / delta;
+                }
+            }
+            hue *= 60;
+            if (hue < 0) hue += 360;
+        }
+        return new float[] {hue, saturation, intensity};
+    }
+
+    /**
+     * Converts a <a href="http://en.wikipedia.org/wiki/HSL_color_space">HSI</a> triplet to an RGB.
+     * 
+     * @param hsi the HSI values
+     * @return the RGB corresponding to the HSI spec
+     */
+    private static RGB fromHSI(float[] hsi) {
+        float r, g, b;
+        float hue= hsi[0];
+        float saturation= hsi[1];
+        float intensity= hsi[2];
+        if (saturation is 0) {
+            r = g = b = intensity; 
+        } else {
+            float temp2= intensity < 0.5f ? intensity * (1.0f + saturation) : (intensity + saturation) - (intensity * saturation);
+            float temp1= 2f * intensity - temp2;
+            if (hue is 360) hue = 0;
+            hue /= 360;
+
+            r= hue2RGB(temp1, temp2, hue + 1f/3f);
+            g= hue2RGB(temp1, temp2, hue);
+            b= hue2RGB(temp1, temp2, hue - 1f/3f);
+        }
+
+        int red = (int)(r * 255 + 0.5);
+        int green = (int)(g * 255 + 0.5);
+        int blue = (int)(b * 255 + 0.5);    
+        return new RGB(red, green, blue);
+    }
+
+    private static float hue2RGB(float t1, float t2, float hue) {
+        if (hue < 0)
+            hue += 1;
+        else if (hue > 1)
+            hue -= 1;
+        if (6f * hue < 1)
+            return t1 +(t2 - t1) * 6f * hue;
+        if (2f * hue < 1)
+            return t2;
+        if (3f * hue < 2)
+            return t1 + (t2 - t1) * (2f/3f - hue) * 6f;
+        return t1;
+    }
+
+    /**
+     * Returns an RGB that lies between the given foreground and background
+     * colors using the given mixing factor. A <code>factor</code> of 1.0 will produce a
+     * color equal to <code>fg</code>, while a <code>factor</code> of 0.0 will produce one
+     * equal to <code>bg</code>.
+     * @param bg the background color
+     * @param fg the foreground color
+     * @param factor the mixing factor, must be in [0,&nbsp;1]
+     * 
+     * @return the interpolated color
+     */
+    public static RGB blend(RGB bg, RGB fg, float factor) {
+        Assert.isLegal(bg !is null);
+        Assert.isLegal(fg !is null);
+        Assert.isLegal(factor >= 0f && factor <= 1f);
+
+        float complement= 1f - factor;
+        return new RGB(
+                (int) (complement * bg.red + factor * fg.red),
+                (int) (complement * bg.green + factor * fg.green),
+                (int) (complement * bg.blue + factor * fg.blue)
+        );
+    }
+
+    /**
+     * Returns an array of colors in a smooth palette from <code>start</code> to <code>end</code>.
+     * <p>
+     * The returned array has size <code>steps</code>, and the color at index 0 is <code>start</code>, the color
+     * at index <code>steps&nbsp;-&nbsp;1</code> is <code>end</code>.
+     * 
+     * @param start the start color of the palette
+     * @param end the end color of the palette
+     * @param steps the requested size, must be &gt; 0
+     * @return an array of <code>steps</code> colors in the palette from <code>start</code> to <code>end</code>
+     */
+    public static RGB[] palette(RGB start, RGB end, int steps) {
+        Assert.isLegal(start !is null);
+        Assert.isLegal(end !is null);
+        Assert.isLegal(steps > 0);
+        
+        if (steps is 1)
+            return new RGB[] { start };
+
+        float step= 1.0f / (steps - 1);
+        RGB[] gradient= new RGB[steps];
+        for (int i= 0; i < steps; i++)
+            gradient[i]= blend(start, end, step * i); 
+
+        return gradient;
+    }
+
+    /**
+     * Returns an array of colors with hues evenly distributed on the hue wheel defined by the <a
+     * href="http://en.wikipedia.org/wiki/HSV_color_space">HSB color space</a>. The returned array
+     * has size <code>steps</code>. The distance <var>d</var> between two successive colors is
+     * in [120&#176;,&nbsp;180&#176;].
+     * <p>
+     * The color at a given <code>index</code> has the hue returned by
+     * {@linkplain #computeHue(int) computeHue(index)}; i.e. the computed hues are not equidistant,
+     * but adaptively distributed on the color wheel.
+     * </p>
+     * <p>
+     * The first six colors returned correspond to the following {@link DWT} color constants:
+     * {@link DWT#COLOR_RED red}, {@link DWT#COLOR_GREEN green}, {@link DWT#COLOR_BLUE blue},
+     * {@link DWT#COLOR_YELLOW yellow}, {@link DWT#COLOR_CYAN cyan},
+     * {@link DWT#COLOR_MAGENTA magenta}.
+     * </p>
+     * 
+     * @param steps the requested size, must be &gt;= 2
+     * @return an array of <code>steps</code> colors evenly distributed on the color wheel
+     */
+    public static RGB[] rainbow(int steps) {
+        Assert.isLegal(steps >= 2);
+
+        RGB[] rainbow= new RGB[steps];
+        for (int i= 0; i < steps; i++)
+            rainbow[i]= new RGB(computeHue(i), 1f, 1f);
+
+        return rainbow;
+    }
+
+    /**
+     * Returns an indexed hue in [0&#176;,&nbsp;360&#176;), distributing the hues evenly on the hue wheel
+     * defined by the <a href="http://en.wikipedia.org/wiki/HSV_color_space">HSB (or HSV) color
+     * space</a>. The distance <var>d</var> between two successive colors is in [120&#176;,&nbsp;180&#176;].
+     * <p>
+     * The first six colors returned correspond to the following {@link DWT} color constants:
+     * {@link DWT#COLOR_RED red}, {@link DWT#COLOR_GREEN green}, {@link DWT#COLOR_BLUE blue},
+     * {@link DWT#COLOR_YELLOW yellow}, {@link DWT#COLOR_CYAN cyan},
+     * {@link DWT#COLOR_MAGENTA magenta}.
+     * </p>
+     * 
+     * @param index the index of the color, must be &gt;= 0
+     * @return a color hue in [0&#176;,&nbsp;360&#176;)
+     * @see RGB#RGB(float, float, float)
+     */
+    public static float computeHue(final int index) {
+        Assert.isLegal(index >= 0);
+        /*
+         * Base 3 gives a nice partitioning for RGB colors with red, green, blue being the colors
+         * 0,1,2, and yellow, cyan, magenta colors 3,4,5.
+         */
+        final int base= 3; 
+        final float range= 360f;
+
+        // partition the baseRange by using the least significant bit to select one half of the
+        // partitioning
+        int baseIndex= index / base;
+        float baseRange= range / base;
+        float baseOffset= 0f;
+        while (baseIndex > 0) {
+            baseRange /= 2;
+            int lsb= baseIndex % 2;
+            baseOffset += lsb * baseRange;
+            baseIndex >>= 1;
+        }
+
+        final int baseMod= index % base;
+        final float hue= baseOffset + baseMod * range / base;
+        Assert.isTrue(hue >= 0 && hue < 360);
+        return hue;
+    }
+
+    private Colors() {
+        // not instantiatable
+    }
+
+}