1 | <?php
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2 | //////////////////////////////////////////////////////////////
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3 | //// ////
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4 | //// p h p U n s h a r p M a s k ////
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5 | //// ////
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6 | //// Unsharp mask algorithm by Torstein Hønsi 2003. ////
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7 | //// thoensi_at_netcom_dot_no ////
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8 | //// Please leave this notice. ////
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9 | //// ////
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10 | //////////////////////////////////////////////////////////////
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11 | /// From: http://vikjavev.no/hovudsida/umtestside.php //
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12 | // //
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13 | // Reformatted by James Heinrich <info@silisoftware.com> //
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14 | // for use in phpThumb() on 3 February 2003. //
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15 | // //
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16 | // phpThumb() is found at http://phpthumb.sourceforge.net ///
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17 | //////////////////////////////////////////////////////////////
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18 |
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19 | /*
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20 | WARNING! Due to a known bug in PHP 4.3.2 this script is not working well in this version.
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21 | The sharpened images get too dark. The bug is fixed in version 4.3.3.
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22 |
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23 | Unsharp masking is a traditional darkroom technique that has proven very suitable for
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24 | digital imaging. The principle of unsharp masking is to create a blurred copy of the image
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25 | and compare it to the underlying original. The difference in colour values
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26 | between the two images is greatest for the pixels near sharp edges. When this
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27 | difference is subtracted from the original image, the edges will be
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28 | accentuated.
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29 |
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30 | The Amount parameter simply says how much of the effect you want. 100 is 'normal'.
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31 | Radius is the radius of the blurring circle of the mask. 'Threshold' is the least
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32 | difference in colour values that is allowed between the original and the mask. In practice
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33 | this means that low-contrast areas of the picture are left unrendered whereas edges
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34 | are treated normally. This is good for pictures of e.g. skin or blue skies.
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35 |
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36 | Any suggenstions for improvement of the algorithm, expecially regarding the speed
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37 | and the roundoff errors in the Gaussian blur process, are welcome.
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38 | */
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39 |
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40 | class phpUnsharpMask {
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41 |
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42 | function applyUnsharpMask(&$img, $amount, $radius, $threshold) {
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43 |
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44 | // $img is an image that is already created within php using
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45 | // imgcreatetruecolor. No url! $img must be a truecolor image.
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46 |
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47 | // Attempt to calibrate the parameters to Photoshop:
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48 | $amount = min($amount, 500);
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49 | $amount = $amount * 0.016;
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50 | if ($amount == 0) {
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51 | return true;
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52 | }
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53 |
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54 | $radius = min($radius, 50);
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55 | $radius = $radius * 2;
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56 |
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57 | $threshold = min($threshold, 255);
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58 |
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59 | $radius = abs(round($radius)); // Only integers make sense.
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60 | if ($radius == 0) {
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61 | return true;
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62 | }
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63 |
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64 | $w = ImageSX($img);
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65 | $h = ImageSY($img);
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66 | $imgCanvas = ImageCreateTrueColor($w, $h);
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67 | $imgCanvas2 = ImageCreateTrueColor($w, $h);
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68 | ImageCopy($imgCanvas, $img, 0, 0, 0, 0, $w, $h);
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69 | ImageCopy($imgCanvas2, $img, 0, 0, 0, 0, $w, $h);
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70 |
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71 |
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72 | $builtinFilterSucceeded = false;
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73 | if ($radius == 1) {
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74 | if (phpthumb_functions::version_compare_replacement(phpversion(), '5.0.0', '>=') && phpthumb_functions::gd_is_bundled()) {
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75 | if (ImageFilter($imgCanvas, IMG_FILTER_GAUSSIAN_BLUR) && ImageFilter($imgCanvas2, IMG_FILTER_GAUSSIAN_BLUR)) {
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76 | $builtinFilterSucceeded = true;
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77 | }
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78 | }
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79 | }
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80 |
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81 | if (!$builtinFilterSucceeded) {
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82 | $imgBlur = ImageCreateTrueColor($w, $h);
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83 | $imgBlur2 = ImageCreateTrueColor($w, $h);
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84 |
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85 | ///////////////////////////
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86 | //
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87 | // Gaussian blur matrix:
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88 | // 1 2 1
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89 | // 2 4 2
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90 | // 1 2 1
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91 | //
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92 | ///////////////////////////
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93 |
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94 | // Move copies of the image around one pixel at the time and merge them with weight
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95 | // according to the matrix. The same matrix is simply repeated for higher radii.
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96 | for ($i = 0; $i < $radius; $i++) {
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97 | ImageCopy ($imgBlur, $imgCanvas, 0, 0, 1, 1, $w - 1, $h - 1); // up left
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98 | ImageCopyMerge($imgBlur, $imgCanvas, 1, 1, 0, 0, $w, $h, 50); // down right
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99 | ImageCopyMerge($imgBlur, $imgCanvas, 0, 1, 1, 0, $w - 1, $h, 33.33333); // down left
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100 | ImageCopyMerge($imgBlur, $imgCanvas, 1, 0, 0, 1, $w, $h - 1, 25); // up right
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101 | ImageCopyMerge($imgBlur, $imgCanvas, 0, 0, 1, 0, $w - 1, $h, 33.33333); // left
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102 | ImageCopyMerge($imgBlur, $imgCanvas, 1, 0, 0, 0, $w, $h, 25); // right
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103 | ImageCopyMerge($imgBlur, $imgCanvas, 0, 0, 0, 1, $w, $h - 1, 20 ); // up
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104 | ImageCopyMerge($imgBlur, $imgCanvas, 0, 1, 0, 0, $w, $h, 16.666667); // down
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105 | ImageCopyMerge($imgBlur, $imgCanvas, 0, 0, 0, 0, $w, $h, 50); // center
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106 | ImageCopy ($imgCanvas, $imgBlur, 0, 0, 0, 0, $w, $h);
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107 |
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108 | // During the loop above the blurred copy darkens, possibly due to a roundoff
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109 | // error. Therefore the sharp picture has to go through the same loop to
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110 | // produce a similar image for comparison. This is not a good thing, as processing
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111 | // time increases heavily.
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112 | ImageCopy ($imgBlur2, $imgCanvas2, 0, 0, 0, 0, $w, $h);
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113 | ImageCopyMerge($imgBlur2, $imgCanvas2, 0, 0, 0, 0, $w, $h, 50);
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114 | ImageCopyMerge($imgBlur2, $imgCanvas2, 0, 0, 0, 0, $w, $h, 33.33333);
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115 | ImageCopyMerge($imgBlur2, $imgCanvas2, 0, 0, 0, 0, $w, $h, 25);
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116 | ImageCopyMerge($imgBlur2, $imgCanvas2, 0, 0, 0, 0, $w, $h, 33.33333);
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117 | ImageCopyMerge($imgBlur2, $imgCanvas2, 0, 0, 0, 0, $w, $h, 25);
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118 | ImageCopyMerge($imgBlur2, $imgCanvas2, 0, 0, 0, 0, $w, $h, 20 );
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119 | ImageCopyMerge($imgBlur2, $imgCanvas2, 0, 0, 0, 0, $w, $h, 16.666667);
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120 | ImageCopyMerge($imgBlur2, $imgCanvas2, 0, 0, 0, 0, $w, $h, 50);
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121 | ImageCopy ($imgCanvas2, $imgBlur2, 0, 0, 0, 0, $w, $h);
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122 | }
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123 | ImageDestroy($imgBlur);
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124 | ImageDestroy($imgBlur2);
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125 | }
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126 |
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127 | // Calculate the difference between the blurred pixels and the original
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128 | // and set the pixels
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129 | for ($x = 0; $x < $w; $x++) { // each row
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130 | for ($y = 0; $y < $h; $y++) { // each pixel
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131 |
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132 | $rgbOrig = ImageColorAt($imgCanvas2, $x, $y);
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133 | $rOrig = (($rgbOrig >> 16) & 0xFF);
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134 | $gOrig = (($rgbOrig >> 8) & 0xFF);
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135 | $bOrig = ($rgbOrig & 0xFF);
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136 |
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137 | $rgbBlur = ImageColorAt($imgCanvas, $x, $y);
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138 | $rBlur = (($rgbBlur >> 16) & 0xFF);
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139 | $gBlur = (($rgbBlur >> 8) & 0xFF);
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140 | $bBlur = ($rgbBlur & 0xFF);
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141 |
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142 | // When the masked pixels differ less from the original
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143 | // than the threshold specifies, they are set to their original value.
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144 | $rNew = (abs($rOrig - $rBlur) >= $threshold) ? max(0, min(255, ($amount * ($rOrig - $rBlur)) + $rOrig)) : $rOrig;
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145 | $gNew = (abs($gOrig - $gBlur) >= $threshold) ? max(0, min(255, ($amount * ($gOrig - $gBlur)) + $gOrig)) : $gOrig;
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146 | $bNew = (abs($bOrig - $bBlur) >= $threshold) ? max(0, min(255, ($amount * ($bOrig - $bBlur)) + $bOrig)) : $bOrig;
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147 |
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148 | if (($rOrig != $rNew) || ($gOrig != $gNew) || ($bOrig != $bNew)) {
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149 | $pixCol = ImageColorAllocate($img, $rNew, $gNew, $bNew);
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150 | ImageSetPixel($img, $x, $y, $pixCol);
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151 | }
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152 | }
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153 | }
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154 | ImageDestroy($imgCanvas);
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155 | ImageDestroy($imgCanvas2);
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156 |
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157 | return true;
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158 | }
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159 |
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160 | }
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161 |
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162 | ?>
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