1 | #!/usr/bin/env python |
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2 | |
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3 | import math, gd, random |
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4 | |
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5 | # Tiny image class to make examples short and readable |
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6 | class Image(gd.image): |
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7 | def __new__(args, truecolor = False): |
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8 | gd.gdMaxColors = 256 * 256 * 256 |
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9 | if truecolor: |
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10 | return gd.image.__new__(args, True) |
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11 | else: |
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12 | return gd.image.__new__(args) |
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13 | def getGray(self, x, y): |
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14 | p = self.getPixel((x, y)) |
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15 | c = self.colorComponents(p)[0] / 255.0 |
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16 | return c |
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17 | def getRgb(self, x, y): |
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18 | p = self.getPixel((x, y)) |
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19 | rgb = self.colorComponents(p) |
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20 | return [rgb[0] / 255.0, rgb[1] / 255.0, rgb[2] / 255.0] |
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21 | def setGray(self, x, y, t): |
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22 | p = (int)(t * 255.999) |
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23 | c = self.colorResolve((p, p, p)) |
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24 | self.setPixel((x, y), c) |
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25 | def setRgb(self, x, y, r, g, b): |
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26 | r = (int)(r * 255.999) |
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27 | g = (int)(g * 255.999) |
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28 | b = (int)(b * 255.999) |
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29 | c = self.colorResolve((r, g, b)) |
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30 | self.setPixel((x, y), c) |
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31 | |
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32 | # Manipulate gamma values |
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33 | class Gamma: |
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34 | def CtoI(x): |
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35 | return math.pow(x, 2.2) |
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36 | def ItoC(x): |
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37 | return math.pow(x, 1 / 2.2) |
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38 | CtoI = staticmethod(CtoI) |
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39 | ItoC = staticmethod(ItoC) |
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40 | |
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41 | # Load the 256x256 grayscale Lenna image |
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42 | lenna256bw = Image("lenna256bw.png") |
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43 | |
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44 | # Create a 32x256 grayscale gradient |
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45 | gradient256bw = Image((32, 256)) |
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46 | for x in range(32): |
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47 | for y in range(256): |
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48 | gradient256bw.setGray(x, 255 - y, y / 255.) |
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49 | gradient256bw.writePng("gradient256bw.png") |
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50 | |
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51 | # Output 1.1.1: 50% threshold |
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52 | # Output 1.1.2: 40% threshold |
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53 | # Output 1.1.3: 60% threshold |
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54 | def test11x(src, threshold, name): |
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55 | (w, h) = src.size() |
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56 | dest = Image((w, h)) |
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57 | for y in range(h): |
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58 | for x in range(w): |
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59 | c = src.getGray(x, y) > threshold |
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60 | dest.setGray(x, y, c) |
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61 | dest.writePng(name) |
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62 | |
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63 | test11x(lenna256bw, 0.5, "out1-1-1.png") |
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64 | test11x(lenna256bw, 0.4, "out1-1-2.png") |
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65 | test11x(lenna256bw, 0.6, "out1-1-3.png") |
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66 | test11x(gradient256bw, 0.5, "grad1-1-1.png") |
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67 | test11x(gradient256bw, 0.4, "grad1-1-2.png") |
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68 | test11x(gradient256bw, 0.6, "grad1-1-3.png") |
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69 | |
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70 | # Output 1.2.1: 3-colour threshold |
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71 | # Output 1.2.2: 5-colour threshold |
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72 | def test12x(src, colors, name): |
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73 | (w, h) = src.size() |
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74 | dest = Image((w, h)) |
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75 | p = -0.0001 + colors |
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76 | q = colors - 1 |
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77 | for y in range(h): |
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78 | for x in range(w): |
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79 | c = src.getGray(x, y) |
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80 | c = math.floor(c * p) / q |
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81 | dest.setGray(x, y, c) |
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82 | dest.writePng(name) |
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83 | |
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84 | test12x(lenna256bw, 3, "out1-2-1.png") |
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85 | test12x(lenna256bw, 5, "out1-2-2.png") |
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86 | test12x(gradient256bw, 3, "grad1-2-1.png") |
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87 | test12x(gradient256bw, 5, "grad1-2-2.png") |
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88 | |
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89 | # Pattern 2.1.1: a 50% halftone pattern with various block sizes |
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90 | dest = Image((320, 80)) |
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91 | for x in range(320): |
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92 | d = 8 >> (x / 80) |
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93 | for y in range(80): |
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94 | c = (x / d + y / d) & 1 |
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95 | dest.setGray(x, y, c) |
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96 | dest.writePng("pat2-1-1.png") |
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97 | |
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98 | # Pattern 2.1.2: 25% and 75% halftone patterns with various block sizes |
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99 | dest = Image((320, 80)) |
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100 | for x in range(320): |
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101 | d = 8 >> (x / 80) |
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102 | for y in range(40): |
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103 | c = ((x / d + y / d) & 1) or (y / d & 1) |
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104 | dest.setGray(x, y, c) |
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105 | for y in range(40, 80): |
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106 | c = ((x / d + y / d) & 1) and (y / d & 1) |
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107 | dest.setGray(x, y, c) |
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108 | dest.writePng("pat2-1-2.png") |
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109 | |
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110 | # Output 2.1.1: 20/40/60/80% threshold with 25/50/75% patterns inbetween: |
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111 | def test211(src, name): |
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112 | (w, h) = src.size() |
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113 | dest = Image((w, h)) |
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114 | for y in range(h): |
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115 | for x in range(w): |
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116 | c = src.getGray(x, y) |
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117 | if c < 0.2: |
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118 | c = 0. |
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119 | elif c < 0.4: |
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120 | c = ((x + y) & 1) and (y & 1) |
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121 | elif c < 0.6: |
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122 | c = (x + y) & 1 |
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123 | elif c < 0.8: |
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124 | c = ((x + y) & 1) or (y & 1) |
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125 | else: |
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126 | c = 1. |
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127 | dest.setGray(x, y, c) |
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128 | dest.writePng(name) |
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129 | |
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130 | test211(lenna256bw, "out2-1-1.png") |
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131 | test211(gradient256bw, "grad2-1-1.png") |
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132 | |
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133 | # Pattern 2.2.1: vertical, mixed and horizontal black-white halftones |
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134 | dest = Image((240, 80)) |
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135 | for y in range(80): |
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136 | for x in range(80): |
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137 | c = x & 1 |
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138 | dest.setGray(x, y, c) |
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139 | for x in range(80, 160): |
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140 | c = (x / d + y / d) & 1 |
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141 | dest.setGray(x, y, c) |
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142 | for x in range(160, 240): |
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143 | c = y & 1 |
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144 | dest.setGray(x, y, c) |
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145 | dest.writePng("pat2-2-1.png") |
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146 | |
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147 | # Pattern 2.2.2: two different 25% patterns |
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148 | dest = Image((320, 80)) |
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149 | for y in range(80): |
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150 | for x in range(80): |
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151 | c = (x / 2 & 1) and (y / 2 & 1) |
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152 | dest.setGray(x, y, c) |
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153 | for x in range(80, 160): |
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154 | c = (x & 1) and (y & 1) |
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155 | dest.setGray(x, y, c) |
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156 | for x in range(160, 240): |
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157 | c = (x & 1) and ((y + x / 2) & 1) |
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158 | dest.setGray(x, y, c) |
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159 | for x in range(240, 320): |
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160 | c = (x / 2 & 1) and ((y / 2 + x / 4) & 1) |
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161 | dest.setGray(x, y, c) |
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162 | dest.writePng("pat2-2-2.png") |
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163 | |
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164 | # Output 2.3.1: 4x4 Bayer dithering |
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165 | # Output 2.3.2: 4x4 cluster dot |
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166 | # Output 2.3.3: 5x3 line dithering |
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167 | def test23x(src, mat, name): |
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168 | (w, h) = src.size() |
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169 | dest = Image((w, h)) |
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170 | dx = len(mat[0]) |
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171 | dy = len(mat) |
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172 | for y in range(h): |
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173 | for x in range(w): |
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174 | c = src.getGray(x, y) |
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175 | threshold = (1. + mat[y % dy][x % dx]) / (dx * dy + 1) |
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176 | c = c > threshold |
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177 | dest.setGray(x, y, c) |
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178 | dest.writePng(name) |
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179 | |
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180 | mat = [[ 0, 8, 3, 11], |
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181 | [ 15, 4, 12, 7], |
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182 | [ 2, 10, 1, 9], |
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183 | [ 13, 6, 14, 5]] |
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184 | test23x(lenna256bw, mat, "out2-3-1.png") |
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185 | test23x(gradient256bw, mat, "grad2-3-1.png") |
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186 | |
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187 | mat = [[ 12, 5, 6, 13], |
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188 | [ 4, 0, 1, 7], |
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189 | [ 11, 3, 2, 8], |
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190 | [ 15, 10, 9, 14]] |
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191 | test23x(lenna256bw, mat, "out2-3-2.png") |
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192 | test23x(gradient256bw, mat, "grad2-3-2.png") |
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193 | |
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194 | mat = [[ 13, 7, 0, 4, 10], |
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195 | [ 9, 3, 1, 8, 14], |
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196 | [ 11, 5, 2, 6, 12],] |
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197 | test23x(lenna256bw, mat, "out2-3-3.png") |
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198 | test23x(gradient256bw, mat, "grad2-3-3.png") |
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199 | |
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200 | # Output 2.4.1: uniform random dithering |
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201 | def test241(src, name): |
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202 | random.seed(0) |
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203 | (w, h) = src.size() |
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204 | dest = Image((w, h)) |
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205 | for y in range(h): |
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206 | for x in range(w): |
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207 | c = src.getGray(x, y) |
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208 | d = c > random.random() |
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209 | dest.setGray(x, y, d) |
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210 | dest.writePng(name) |
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211 | |
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212 | test241(lenna256bw, "out2-4-1.png") |
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213 | test241(gradient256bw, "grad2-4-1.png") |
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214 | |
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215 | # Output 2.4.2: random dithering |
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216 | def test242(src, name): |
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217 | random.seed(0) |
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218 | (w, h) = src.size() |
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219 | dest = Image((w, h)) |
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220 | for y in range(h): |
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221 | for x in range(w): |
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222 | c = src.getGray(x, y) |
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223 | d = c > random.gauss(0.5, 0.15) |
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224 | dest.setGray(x, y, d) |
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225 | dest.writePng(name) |
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226 | |
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227 | test242(lenna256bw, "out2-4-2.png") |
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228 | test242(gradient256bw, "grad2-4-2.png") |
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229 | |
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230 | # Output 3.1.1: standard Floyd-Steinberg |
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231 | def test311(src, name): |
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232 | (w, h) = src.size() |
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233 | dest = Image((w, h)) |
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234 | ep = [0.] * (w + 2) |
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235 | for y in range(h): |
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236 | ey = [0.] * (w + 2) |
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237 | ex = 0 |
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238 | for x in range(w): |
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239 | c = src.getGray(x, y) + ex + ep[x + 1] |
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240 | d = c > 0.5 |
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241 | dest.setGray(x, y, d) |
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242 | error = c - d |
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243 | ex = error * 7. / 16. |
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244 | ey[x] += error * 3. / 16. |
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245 | ey[x + 1] += error * 5. / 16. |
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246 | ey[x + 2] += error * 1. / 16. |
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247 | ep = ey |
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248 | dest.writePng(name) |
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249 | |
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250 | test311(lenna256bw, "out3-1-1.png") |
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251 | test311(gradient256bw, "grad3-1-1.png") |
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252 | |
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253 | # Output 3.1.2: serpentine Floyd-Steinberg |
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254 | def test312(src, name): |
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255 | (w, h) = src.size() |
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256 | dest = Image((w, h)) |
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257 | ep = [0.] * (w + 2) |
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258 | for z in range(h / 2): |
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259 | ey = [0.] * (w + 2) |
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260 | ex = 0 |
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261 | y = z * 2 |
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262 | for x in range(w): |
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263 | c = src.getGray(x, y) + ex + ep[x + 1] |
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264 | d = c > 0.5 |
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265 | dest.setGray(x, y, d) |
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266 | error = c - d |
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267 | ex = error * 7. / 16. |
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268 | ey[x] += error * 3. / 16. |
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269 | ey[x + 1] += error * 5. / 16. |
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270 | ey[x + 2] += error * 1. / 16. |
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271 | ep = ey |
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272 | ey = [0.] * (w + 2) |
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273 | ex = 0 |
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274 | y = z * 2 + 1 |
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275 | for x in range(w - 1, -1, -1): |
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276 | c = src.getGray(x, y) + ex + ep[x + 1] |
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277 | d = c > 0.5 |
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278 | dest.setGray(x, y, d) |
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279 | error = c - d |
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280 | ex = error * 7. / 16. |
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281 | ey[x] += error * 1. / 16. |
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282 | ey[x + 1] += error * 5. / 16. |
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283 | ey[x + 2] += error * 3. / 16. |
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284 | ep = ey |
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285 | dest.writePng(name) |
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286 | |
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287 | test312(lenna256bw, "out3-1-2.png") |
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288 | test312(gradient256bw, "grad3-1-2.png") |
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289 | |
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290 | # Output 3.2.1: Fan (modified Floyd-Steinberg) |
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291 | def test321(src, name): |
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292 | (w, h) = src.size() |
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293 | dest = Image((w, h)) |
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294 | ep = [0.] * (w + 3) |
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295 | for y in range(h): |
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296 | ey = [0.] * (w + 3) |
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297 | ex = 0 |
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298 | for x in range(w): |
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299 | c = src.getGray(x, y) + ex + ep[x + 2] |
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300 | d = c > 0.5 |
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301 | dest.setGray(x, y, d) |
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302 | error = c - d |
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303 | ex = error * 7. / 16. |
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304 | ey[x] += error * 1. / 16. |
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305 | ey[x + 1] += error * 3. / 16. |
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306 | ey[x + 2] += error * 5. / 16. |
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307 | ep = ey |
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308 | dest.writePng(name) |
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309 | |
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310 | test321(lenna256bw, "out3-2-1.png") |
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311 | test321(gradient256bw, "grad3-2-1.png") |
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312 | |
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313 | # Output 3.2.2: Jarvis, Judice and Ninke |
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314 | def test322(src, name): |
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315 | (w, h) = src.size() |
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316 | dest = Image((w, h)) |
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317 | ep = [0.] * (w + 4) |
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318 | ey = [0.] * (w + 4) |
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319 | for y in range(h): |
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320 | ey2 = [0.] * (w + 4) |
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321 | ex = 0 |
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322 | ex2 = 0 |
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323 | for x in range(w): |
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324 | c = src.getGray(x, y) + ex + ep[x + 2] |
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325 | d = c > 0.5 |
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326 | dest.setGray(x, y, d) |
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327 | error = c - d |
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328 | ex = ex2 + error * 7. / 48. |
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329 | ex2 = error * 5. / 48. |
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330 | ey[x] += error * 3. / 48. |
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331 | ey[x + 1] += error * 5. / 48. |
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332 | ey[x + 2] += error * 7. / 48. |
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333 | ey[x + 3] += error * 5. / 48. |
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334 | ey[x + 4] += error * 3. / 48. |
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335 | ey2[x] += error * 1. / 48. |
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336 | ey2[x + 1] += error * 3. / 48. |
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337 | ey2[x + 2] += error * 5. / 48. |
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338 | ey2[x + 3] += error * 3. / 48. |
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339 | ey2[x + 4] += error * 1. / 48. |
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340 | ep = ey |
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341 | ey = ey2 |
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342 | dest.writePng(name) |
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343 | |
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344 | test322(lenna256bw, "out3-2-2.png") |
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345 | test322(gradient256bw, "grad3-2-2.png") |
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346 | |
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347 | # Output 3-2-3: Stucki |
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348 | # TODO: merge with Jarvis-Judice-Ninke |
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349 | def test323(src, name): |
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350 | (w, h) = src.size() |
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351 | dest = Image((w, h)) |
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352 | ep = [0.] * (w + 4) |
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353 | ey = [0.] * (w + 4) |
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354 | for y in range(h): |
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355 | ey2 = [0.] * (w + 4) |
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356 | ex = 0 |
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357 | ex2 = 0 |
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358 | for x in range(w): |
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359 | c = src.getGray(x, y) + ex + ep[x + 2] |
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360 | d = c > 0.5 |
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361 | dest.setGray(x, y, d) |
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362 | error = c - d |
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363 | ex = ex2 + error * 8. / 42. |
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364 | ex2 = error * 4. / 42. |
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365 | ey[x] += error * 2. / 42. |
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366 | ey[x + 1] += error * 4. / 42. |
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367 | ey[x + 2] += error * 8. / 42. |
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368 | ey[x + 3] += error * 4. / 42. |
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369 | ey[x + 4] += error * 2. / 42. |
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370 | ey2[x] += error * 1. / 42. |
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371 | ey2[x + 1] += error * 2. / 42. |
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372 | ey2[x + 2] += error * 4. / 42. |
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373 | ey2[x + 3] += error * 2. / 42. |
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374 | ey2[x + 4] += error * 1. / 42. |
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375 | ep = ey |
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376 | ey = ey2 |
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377 | dest.writePng(name) |
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378 | |
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379 | test323(lenna256bw, "out3-2-3.png") |
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380 | test323(gradient256bw, "grad3-2-3.png") |
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381 | |
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382 | # Output 3-2-4: Burkes |
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383 | # TODO: merge with Jarvis-Judice-Ninke and Stucki |
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384 | def test324(src, name): |
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385 | (w, h) = src.size() |
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386 | dest = Image((w, h)) |
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387 | ep = [0.] * (w + 4) |
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388 | for y in range(h): |
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389 | ey = [0.] * (w + 4) |
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390 | ex = 0 |
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391 | ex2 = 0 |
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392 | for x in range(w): |
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393 | c = src.getGray(x, y) + ex + ep[x + 2] |
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394 | d = c > 0.5 |
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395 | dest.setGray(x, y, d) |
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396 | error = c - d |
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397 | ex = ex2 + error * 8. / 32. |
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398 | ex2 = error * 4. / 32. |
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399 | ey[x] += error * 2. / 32. |
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400 | ey[x + 1] += error * 4. / 32. |
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401 | ey[x + 2] += error * 8. / 32. |
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402 | ey[x + 3] += error * 4. / 32. |
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403 | ey[x + 4] += error * 2. / 32. |
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404 | ep = ey |
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405 | dest.writePng(name) |
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406 | |
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407 | test324(lenna256bw, "out3-2-4.png") |
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408 | test324(gradient256bw, "grad3-2-4.png") |
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409 | |
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410 | ############################################################################## |
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411 | # Only temporary cruft below this |
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412 | import sys |
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413 | sys.exit(0) |
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414 | |
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415 | |
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416 | |
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417 | |
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418 | # Pattern 4: gamma-corrected 50% gray, black-white halftone, 50% gray |
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419 | dest = Image((240, 80)) |
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420 | for y in range(80): |
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421 | for x in range(80): |
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422 | dest.setGray(x, y, Gamma.ItoC(0.5)) |
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423 | for x in range(80, 160): |
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424 | c = (x + y) & 1 |
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425 | dest.setGray(x, y, c) |
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426 | for x in range(160, 240): |
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427 | dest.setGray(x, y, 0.5) |
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428 | dest.writePng("pat004.png") |
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429 | |
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430 | # Pattern 5: gamma-corrected 50% gray, black-white halftone, 50% gray |
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431 | dest = Image((400, 240)) |
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432 | for y in range(80): |
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433 | for x in range(400): |
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434 | if x < 80: |
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435 | c = 0. |
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436 | elif x < 160: |
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437 | c = ((x + y) & 1) and (y & 1) |
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438 | elif x < 240: |
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439 | c = (x + y) & 1 |
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440 | elif x < 320: |
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441 | c = ((x + y) & 1) or (y & 1) |
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442 | else: |
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443 | c = 1. |
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444 | dest.setGray(x, y, c) |
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445 | for y in range(80, 160): |
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446 | for x in range(400): |
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447 | dest.setGray(x, y, x / 80 / 4.) |
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448 | for y in range(160, 240): |
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449 | for x in range(400): |
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450 | if x < 80: |
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451 | c = 0. |
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452 | elif x < 160: |
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453 | c = (((x + y) & 3) == 1) and ((y & 3) == 1) |
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454 | elif x < 240: |
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455 | c = ((x + y) & 1) and (y & 1) |
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456 | elif x < 320: |
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457 | c = (x + y) & 1 |
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458 | else: |
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459 | c = 1. |
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460 | dest.setGray(x, y, c) |
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461 | dest.writePng("pat005.png") |
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462 | |
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463 | # Output 6: gamma-aware 20/40/60/80% threshold: |
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464 | def test4(src, name): |
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465 | (w, h) = src.size() |
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466 | dest = Image((w, h)) |
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467 | for y in range(h): |
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468 | for x in range(w): |
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469 | c = src.getGray(x, y) |
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470 | if c < 0.2: |
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471 | c = 0. |
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472 | elif c < 0.4: |
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473 | c = (((x + y) & 3) == 1) and ((y & 3) == 1) |
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474 | elif c < 0.6: |
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475 | c = ((x + y) & 1) and (y & 1) |
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476 | elif c < 0.8: |
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477 | c = (x + y) & 1 |
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478 | else: |
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479 | c = 1. |
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480 | dest.setGray(x, y, c) |
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481 | dest.writePng(name) |
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482 | |
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483 | test4(lenna256bw, "out007.png") |
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484 | test4(gradient256bw, "grad007.png") |
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485 | |
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486 | |
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487 | src = lenna256bw |
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488 | src = gradient256bw |
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489 | (w, h) = src.size() |
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490 | |
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491 | mat = [[ 0, 8, 3, 11], |
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492 | [ 15, 4, 12, 7], |
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493 | [ 2, 10, 1, 9], |
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494 | [ 13, 6, 14, 5]] |
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495 | #mat = [[ 6, 7, 8, 9], |
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496 | # [ 5, 0, 1, 10], |
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497 | # [ 4, 3, 2, 11], |
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498 | # [ 15, 14, 13, 12]] |
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499 | #mat = [[ 12, 5, 9, 13], |
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500 | # [ 8, 0, 1, 6], |
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501 | # [ 4, 3, 2, 10], |
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502 | # [ 15, 11, 7, 14]] |
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503 | size = 4 |
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504 | #mat = [[ 35, 24, 13, 14, 25, 32], |
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505 | # [ 31, 12, 5, 6, 15, 26], |
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506 | # [ 23, 4, 0, 1, 7, 16], |
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507 | # [ 22, 11, 3, 2, 8, 17], |
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508 | # [ 30, 21, 10, 9, 18, 27], |
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509 | # [ 34, 29, 20, 19, 28, 33]] |
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510 | #mat = [[ 0, 20, 30, 3, 23, 29], |
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511 | # [ 12, 32, 18, 15, 35, 17], |
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512 | # [ 27, 8, 4, 24, 11, 7], |
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513 | # [ 2, 22, 28, 1, 21, 31], |
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514 | # [ 14, 34, 16, 13, 33, 19], |
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515 | # [ 25, 10, 6, 26, 9, 5]] |
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516 | #size = 6 |
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517 | dest = Image((w, h)) |
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518 | for y in range(h): |
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519 | for x in range(w): |
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520 | c = src.getGray(x, y) |
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521 | i = Gamma.CtoI(c) |
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522 | threshold = mat[x % size][y % size] |
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523 | d = math.floor(i * (size * size + .9999)) > threshold |
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524 | if c > 0.95: |
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525 | print c, i, i * (size * size + .9999) |
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526 | c = d |
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527 | dest.setGray(x, y, c) |
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528 | dest.writePng("out008.png") |
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529 | |
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530 | # Create a dot-matrix pattern |
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531 | mat = [[0, 2, 2, 3, 1], |
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532 | [2, 2, 0, 2, 3], |
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533 | [2, 0, 1, 1, 3], |
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534 | [3, 2, 1, 0, 3], |
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535 | [1, 3, 3, 3, 3]] |
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536 | dest = Image((320, 64)) |
---|
537 | for x in range(320): |
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538 | d = x / 64 |
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539 | for y in range(64): |
---|
540 | c = mat[y % 5][x % 5] >= d |
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541 | dest.setGray(x, y, c) |
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542 | dest.writePng("pat003.png") |
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543 | |
---|