source: trunk/www.guidonia.net/wp/wp-content/plugins/ferdinand-wordbook/phpthumb/phpthumb.unsharp.php@ 44

Last change on this file since 44 was 44, checked in by luciano, 15 years ago
File size: 6.9 KB
Line 
1<?php
2//////////////////////////////////////////////////////////////
3//// ////
4//// p h p U n s h a r p M a s k ////
5//// ////
6//// Unsharp mask algorithm by Torstein Hønsi 2003. ////
7//// thoensi_at_netcom_dot_no ////
8//// Please leave this notice. ////
9//// ////
10//////////////////////////////////////////////////////////////
11/// From: http://vikjavev.no/hovudsida/umtestside.php //
12// //
13// Reformatted by James Heinrich <info@silisoftware.com> //
14// for use in phpThumb() on 3 February 2003. //
15// //
16// phpThumb() is found at http://phpthumb.sourceforge.net ///
17//////////////////////////////////////////////////////////////
18
19/*
20WARNING! Due to a known bug in PHP 4.3.2 this script is not working well in this version.
21The sharpened images get too dark. The bug is fixed in version 4.3.3.
22
23Unsharp masking is a traditional darkroom technique that has proven very suitable for
24digital imaging. The principle of unsharp masking is to create a blurred copy of the image
25and compare it to the underlying original. The difference in colour values
26between the two images is greatest for the pixels near sharp edges. When this
27difference is subtracted from the original image, the edges will be
28accentuated.
29
30The Amount parameter simply says how much of the effect you want. 100 is 'normal'.
31Radius is the radius of the blurring circle of the mask. 'Threshold' is the least
32difference in colour values that is allowed between the original and the mask. In practice
33this means that low-contrast areas of the picture are left unrendered whereas edges
34are treated normally. This is good for pictures of e.g. skin or blue skies.
35
36Any suggenstions for improvement of the algorithm, expecially regarding the speed
37and the roundoff errors in the Gaussian blur process, are welcome.
38*/
39
40class phpUnsharpMask {
41
42 function applyUnsharpMask(&$img, $amount, $radius, $threshold) {
43
44 // $img is an image that is already created within php using
45 // imgcreatetruecolor. No url! $img must be a truecolor image.
46
47 // Attempt to calibrate the parameters to Photoshop:
48 $amount = min($amount, 500);
49 $amount = $amount * 0.016;
50 if ($amount == 0) {
51 return true;
52 }
53
54 $radius = min($radius, 50);
55 $radius = $radius * 2;
56
57 $threshold = min($threshold, 255);
58
59 $radius = abs(round($radius)); // Only integers make sense.
60 if ($radius == 0) {
61 return true;
62 }
63
64 $w = ImageSX($img);
65 $h = ImageSY($img);
66 $imgCanvas = ImageCreateTrueColor($w, $h);
67 $imgCanvas2 = ImageCreateTrueColor($w, $h);
68 ImageCopy($imgCanvas, $img, 0, 0, 0, 0, $w, $h);
69 ImageCopy($imgCanvas2, $img, 0, 0, 0, 0, $w, $h);
70
71
72 $builtinFilterSucceeded = false;
73 if ($radius == 1) {
74 if (phpthumb_functions::version_compare_replacement(phpversion(), '5.0.0', '>=') && phpthumb_functions::gd_is_bundled()) {
75 if (ImageFilter($imgCanvas, IMG_FILTER_GAUSSIAN_BLUR) && ImageFilter($imgCanvas2, IMG_FILTER_GAUSSIAN_BLUR)) {
76 $builtinFilterSucceeded = true;
77 }
78 }
79 }
80
81 if (!$builtinFilterSucceeded) {
82 $imgBlur = ImageCreateTrueColor($w, $h);
83 $imgBlur2 = ImageCreateTrueColor($w, $h);
84
85 ///////////////////////////
86 //
87 // Gaussian blur matrix:
88 // 1 2 1
89 // 2 4 2
90 // 1 2 1
91 //
92 ///////////////////////////
93
94 // Move copies of the image around one pixel at the time and merge them with weight
95 // according to the matrix. The same matrix is simply repeated for higher radii.
96 for ($i = 0; $i < $radius; $i++) {
97 ImageCopy ($imgBlur, $imgCanvas, 0, 0, 1, 1, $w - 1, $h - 1); // up left
98 ImageCopyMerge($imgBlur, $imgCanvas, 1, 1, 0, 0, $w, $h, 50); // down right
99 ImageCopyMerge($imgBlur, $imgCanvas, 0, 1, 1, 0, $w - 1, $h, 33.33333); // down left
100 ImageCopyMerge($imgBlur, $imgCanvas, 1, 0, 0, 1, $w, $h - 1, 25); // up right
101 ImageCopyMerge($imgBlur, $imgCanvas, 0, 0, 1, 0, $w - 1, $h, 33.33333); // left
102 ImageCopyMerge($imgBlur, $imgCanvas, 1, 0, 0, 0, $w, $h, 25); // right
103 ImageCopyMerge($imgBlur, $imgCanvas, 0, 0, 0, 1, $w, $h - 1, 20 ); // up
104 ImageCopyMerge($imgBlur, $imgCanvas, 0, 1, 0, 0, $w, $h, 16.666667); // down
105 ImageCopyMerge($imgBlur, $imgCanvas, 0, 0, 0, 0, $w, $h, 50); // center
106 ImageCopy ($imgCanvas, $imgBlur, 0, 0, 0, 0, $w, $h);
107
108 // During the loop above the blurred copy darkens, possibly due to a roundoff
109 // error. Therefore the sharp picture has to go through the same loop to
110 // produce a similar image for comparison. This is not a good thing, as processing
111 // time increases heavily.
112 ImageCopy ($imgBlur2, $imgCanvas2, 0, 0, 0, 0, $w, $h);
113 ImageCopyMerge($imgBlur2, $imgCanvas2, 0, 0, 0, 0, $w, $h, 50);
114 ImageCopyMerge($imgBlur2, $imgCanvas2, 0, 0, 0, 0, $w, $h, 33.33333);
115 ImageCopyMerge($imgBlur2, $imgCanvas2, 0, 0, 0, 0, $w, $h, 25);
116 ImageCopyMerge($imgBlur2, $imgCanvas2, 0, 0, 0, 0, $w, $h, 33.33333);
117 ImageCopyMerge($imgBlur2, $imgCanvas2, 0, 0, 0, 0, $w, $h, 25);
118 ImageCopyMerge($imgBlur2, $imgCanvas2, 0, 0, 0, 0, $w, $h, 20 );
119 ImageCopyMerge($imgBlur2, $imgCanvas2, 0, 0, 0, 0, $w, $h, 16.666667);
120 ImageCopyMerge($imgBlur2, $imgCanvas2, 0, 0, 0, 0, $w, $h, 50);
121 ImageCopy ($imgCanvas2, $imgBlur2, 0, 0, 0, 0, $w, $h);
122 }
123 ImageDestroy($imgBlur);
124 ImageDestroy($imgBlur2);
125 }
126
127 // Calculate the difference between the blurred pixels and the original
128 // and set the pixels
129 for ($x = 0; $x < $w; $x++) { // each row
130 for ($y = 0; $y < $h; $y++) { // each pixel
131
132 $rgbOrig = ImageColorAt($imgCanvas2, $x, $y);
133 $rOrig = (($rgbOrig >> 16) & 0xFF);
134 $gOrig = (($rgbOrig >> 8) & 0xFF);
135 $bOrig = ($rgbOrig & 0xFF);
136
137 $rgbBlur = ImageColorAt($imgCanvas, $x, $y);
138 $rBlur = (($rgbBlur >> 16) & 0xFF);
139 $gBlur = (($rgbBlur >> 8) & 0xFF);
140 $bBlur = ($rgbBlur & 0xFF);
141
142 // When the masked pixels differ less from the original
143 // than the threshold specifies, they are set to their original value.
144 $rNew = (abs($rOrig - $rBlur) >= $threshold) ? max(0, min(255, ($amount * ($rOrig - $rBlur)) + $rOrig)) : $rOrig;
145 $gNew = (abs($gOrig - $gBlur) >= $threshold) ? max(0, min(255, ($amount * ($gOrig - $gBlur)) + $gOrig)) : $gOrig;
146 $bNew = (abs($bOrig - $bBlur) >= $threshold) ? max(0, min(255, ($amount * ($bOrig - $bBlur)) + $bOrig)) : $bOrig;
147
148 if (($rOrig != $rNew) || ($gOrig != $gNew) || ($bOrig != $bNew)) {
149 $pixCol = ImageColorAllocate($img, $rNew, $gNew, $bNew);
150 ImageSetPixel($img, $x, $y, $pixCol);
151 }
152 }
153 }
154 ImageDestroy($imgCanvas);
155 ImageDestroy($imgCanvas2);
156
157 return true;
158 }
159
160}
161
162?>
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