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1 /*******************************************************************************
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2 * Copyright (c) 2006, 2007 IBM Corporation and others.
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3 * All rights reserved. This program and the accompanying materials
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4 * are made available under the terms of the Eclipse Public License v1.0
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5 * which accompanies this distribution, and is available at
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6 * http://www.eclipse.org/legal/epl-v10.html
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7 *
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8 * Contributors:
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9 * IBM Corporation - initial API and implementation
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10 * Port to the D programming language:
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11 * Frank Benoit <benoit@tionex.de>
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12 *******************************************************************************/
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13 module dwtx.jface.internal.text.revisions.Colors;
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14
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15 import dwt.dwthelper.utils;
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16
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17
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18 import dwt.DWT;
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19 import dwt.graphics.RGB;
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20 import dwtx.core.runtime.Assert;
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21
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22 /**
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23 * Utility for color operations.
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24 *
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25 * @since 3.3
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26 */
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27 public final class Colors {
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28 /*
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29 * Implementation note: Color computation assumes sRGB, which is probably not true, and does not
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30 * always give good results. CIE based algorithms would be better, see
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31 * http://www.w3.org/TR/PNG-ColorAppendix.html and http://en.wikipedia.org/wiki/Lab_color_space
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32 */
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33
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34 /**
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35 * Returns the human-perceived brightness of a color as float in [0.0, 1.0]. The used RGB
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36 * weights come from http://www.poynton.com/notes/colour_and_gamma/ColorFAQ.html#RTFToC9.
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37 *
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38 * @param rgb the color
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39 * @return the gray-scale value
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40 */
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41 public static float brightness(RGB rgb) {
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42 return Math.min(1f, (0.2126f * rgb.red + 0.7152f * rgb.green + 0.0722f * rgb.blue + 0.5f) / 255f);
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43 }
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44
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45 /**
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46 * Normalizes a color in its perceived brightness. Yellows are darkened, while blues and reds
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47 * are lightened. Depending on the hue, the brightness range within the RGB gamut may be
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48 * different, outside values are clipped. Note that this is an approximation; the returned RGB
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49 * is not guaranteed to have the requested {@link #brightness(RGB) brightness}.
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50 *
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51 * @param color the color to normalize
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52 * @param brightness the requested brightness, in [0, 1]
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53 * @return a normalized version of <code>color</code>
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54 * @see #brightness(RGB)
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55 */
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56 public static RGB adjustBrightness(RGB color, float brightness) {
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57 float[] hsi= toHSI(color);
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58 float psychoFactor= brightness - brightness(color);
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59 float weight= 0.5f; // found by trial and error
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60 hsi[2]= Math.max(0, Math.min(1.0f, hsi[2] + psychoFactor * weight));
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61 color= fromHSI(hsi);
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62 return color;
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63 }
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64
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65 /**
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66 * Converts an {@link RGB} to an <a href="http://en.wikipedia.org/wiki/HSL_color_space">HSI</a>
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67 * triplet.
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68 *
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69 * @param color the color to convert
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70 * @return the HSI float array of length 3
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71 */
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72 private static float[] toHSI(RGB color) {
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73 float r = color.red / 255f;
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74 float g = color.green / 255f;
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75 float b = color.blue / 255f;
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76 float max = Math.max(Math.max(r, g), b);
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77 float min = Math.min(Math.min(r, g), b);
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78 float delta = max - min;
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79 float maxPlusMin= max + min;
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80 float intensity = maxPlusMin / 2;
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81 float saturation= intensity < 0.5 ? delta / maxPlusMin : delta / (2 - maxPlusMin);
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82
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83 float hue = 0;
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84 if (delta !is 0) {
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85 if (r is max) {
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86 hue = (g - b) / delta;
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87 } else {
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88 if (g is max) {
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89 hue = 2 + (b - r) / delta;
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90 } else {
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91 hue = 4 + (r - g) / delta;
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92 }
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93 }
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94 hue *= 60;
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95 if (hue < 0) hue += 360;
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96 }
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97 return new float[] {hue, saturation, intensity};
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98 }
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99
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100 /**
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101 * Converts a <a href="http://en.wikipedia.org/wiki/HSL_color_space">HSI</a> triplet to an RGB.
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102 *
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103 * @param hsi the HSI values
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104 * @return the RGB corresponding to the HSI spec
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105 */
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106 private static RGB fromHSI(float[] hsi) {
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107 float r, g, b;
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108 float hue= hsi[0];
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109 float saturation= hsi[1];
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110 float intensity= hsi[2];
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111 if (saturation is 0) {
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112 r = g = b = intensity;
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113 } else {
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114 float temp2= intensity < 0.5f ? intensity * (1.0f + saturation) : (intensity + saturation) - (intensity * saturation);
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115 float temp1= 2f * intensity - temp2;
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116 if (hue is 360) hue = 0;
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117 hue /= 360;
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118
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119 r= hue2RGB(temp1, temp2, hue + 1f/3f);
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120 g= hue2RGB(temp1, temp2, hue);
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121 b= hue2RGB(temp1, temp2, hue - 1f/3f);
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122 }
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123
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124 int red = (int)(r * 255 + 0.5);
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125 int green = (int)(g * 255 + 0.5);
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126 int blue = (int)(b * 255 + 0.5);
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127 return new RGB(red, green, blue);
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128 }
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129
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130 private static float hue2RGB(float t1, float t2, float hue) {
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131 if (hue < 0)
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132 hue += 1;
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133 else if (hue > 1)
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134 hue -= 1;
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135 if (6f * hue < 1)
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136 return t1 +(t2 - t1) * 6f * hue;
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137 if (2f * hue < 1)
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138 return t2;
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139 if (3f * hue < 2)
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140 return t1 + (t2 - t1) * (2f/3f - hue) * 6f;
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141 return t1;
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142 }
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143
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144 /**
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145 * Returns an RGB that lies between the given foreground and background
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146 * colors using the given mixing factor. A <code>factor</code> of 1.0 will produce a
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147 * color equal to <code>fg</code>, while a <code>factor</code> of 0.0 will produce one
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148 * equal to <code>bg</code>.
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149 * @param bg the background color
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150 * @param fg the foreground color
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151 * @param factor the mixing factor, must be in [0, 1]
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152 *
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153 * @return the interpolated color
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154 */
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155 public static RGB blend(RGB bg, RGB fg, float factor) {
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156 Assert.isLegal(bg !is null);
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157 Assert.isLegal(fg !is null);
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158 Assert.isLegal(factor >= 0f && factor <= 1f);
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159
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160 float complement= 1f - factor;
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161 return new RGB(
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162 (int) (complement * bg.red + factor * fg.red),
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163 (int) (complement * bg.green + factor * fg.green),
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164 (int) (complement * bg.blue + factor * fg.blue)
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165 );
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166 }
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167
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168 /**
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169 * Returns an array of colors in a smooth palette from <code>start</code> to <code>end</code>.
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170 * <p>
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171 * The returned array has size <code>steps</code>, and the color at index 0 is <code>start</code>, the color
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172 * at index <code>steps - 1</code> is <code>end</code>.
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173 *
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174 * @param start the start color of the palette
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175 * @param end the end color of the palette
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176 * @param steps the requested size, must be > 0
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177 * @return an array of <code>steps</code> colors in the palette from <code>start</code> to <code>end</code>
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178 */
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179 public static RGB[] palette(RGB start, RGB end, int steps) {
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180 Assert.isLegal(start !is null);
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181 Assert.isLegal(end !is null);
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182 Assert.isLegal(steps > 0);
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183
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184 if (steps is 1)
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185 return new RGB[] { start };
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186
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187 float step= 1.0f / (steps - 1);
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188 RGB[] gradient= new RGB[steps];
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189 for (int i= 0; i < steps; i++)
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190 gradient[i]= blend(start, end, step * i);
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191
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192 return gradient;
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193 }
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194
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195 /**
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196 * Returns an array of colors with hues evenly distributed on the hue wheel defined by the <a
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197 * href="http://en.wikipedia.org/wiki/HSV_color_space">HSB color space</a>. The returned array
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198 * has size <code>steps</code>. The distance <var>d</var> between two successive colors is
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199 * in [120°, 180°].
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200 * <p>
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201 * The color at a given <code>index</code> has the hue returned by
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202 * {@linkplain #computeHue(int) computeHue(index)}; i.e. the computed hues are not equidistant,
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203 * but adaptively distributed on the color wheel.
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204 * </p>
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205 * <p>
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206 * The first six colors returned correspond to the following {@link DWT} color constants:
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207 * {@link DWT#COLOR_RED red}, {@link DWT#COLOR_GREEN green}, {@link DWT#COLOR_BLUE blue},
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208 * {@link DWT#COLOR_YELLOW yellow}, {@link DWT#COLOR_CYAN cyan},
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209 * {@link DWT#COLOR_MAGENTA magenta}.
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210 * </p>
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211 *
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212 * @param steps the requested size, must be >= 2
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213 * @return an array of <code>steps</code> colors evenly distributed on the color wheel
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214 */
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215 public static RGB[] rainbow(int steps) {
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216 Assert.isLegal(steps >= 2);
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217
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218 RGB[] rainbow= new RGB[steps];
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219 for (int i= 0; i < steps; i++)
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220 rainbow[i]= new RGB(computeHue(i), 1f, 1f);
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221
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222 return rainbow;
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223 }
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224
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225 /**
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226 * Returns an indexed hue in [0°, 360°), distributing the hues evenly on the hue wheel
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227 * defined by the <a href="http://en.wikipedia.org/wiki/HSV_color_space">HSB (or HSV) color
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228 * space</a>. The distance <var>d</var> between two successive colors is in [120°, 180°].
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229 * <p>
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230 * The first six colors returned correspond to the following {@link DWT} color constants:
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231 * {@link DWT#COLOR_RED red}, {@link DWT#COLOR_GREEN green}, {@link DWT#COLOR_BLUE blue},
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232 * {@link DWT#COLOR_YELLOW yellow}, {@link DWT#COLOR_CYAN cyan},
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233 * {@link DWT#COLOR_MAGENTA magenta}.
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234 * </p>
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235 *
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236 * @param index the index of the color, must be >= 0
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237 * @return a color hue in [0°, 360°)
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238 * @see RGB#RGB(float, float, float)
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239 */
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240 public static float computeHue(final int index) {
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241 Assert.isLegal(index >= 0);
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242 /*
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243 * Base 3 gives a nice partitioning for RGB colors with red, green, blue being the colors
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244 * 0,1,2, and yellow, cyan, magenta colors 3,4,5.
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245 */
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246 final int base= 3;
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247 final float range= 360f;
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248
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249 // partition the baseRange by using the least significant bit to select one half of the
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250 // partitioning
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251 int baseIndex= index / base;
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252 float baseRange= range / base;
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253 float baseOffset= 0f;
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254 while (baseIndex > 0) {
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255 baseRange /= 2;
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256 int lsb= baseIndex % 2;
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257 baseOffset += lsb * baseRange;
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258 baseIndex >>= 1;
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259 }
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260
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261 final int baseMod= index % base;
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262 final float hue= baseOffset + baseMod * range / base;
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263 Assert.isTrue(hue >= 0 && hue < 360);
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264 return hue;
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265 }
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266
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267 private Colors() {
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268 // not instantiatable
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269 }
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270
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271 }
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