1: <?php
2: //////////////////////////////////////////////////////////////
3: ////
4: //// Unsharp Mask for PHP - version 2.1.1
5: ////
6: //// Unsharp mask algorithm by Torstein Hønsi 2003-07.
7: //// thoensi_at_netcom_dot_no.
8: //// Please leave this notice.
9: ////
10: //////////////////////////////////////////////////////////////
11: // From: http://vikjavev.no/computing/ump.php //
12: // //
13: // Reformatted by James Heinrich <info@silisoftware.com> //
14: // for use in phpThumb() on 3 February 2003. //
15: // updated to v2.1.1 on 24 April 2011 //
16: // //
17: // phpThumb() is found at http://phpthumb.sourceforge.net //
18: // and/or https://github.com/JamesHeinrich/phpThumb //
19: //////////////////////////////////////////////////////////////
20:
21: /*
22: New:
23: - In version 2.1 (February 26 2007) Tom Bishop has done some important speed enhancements.
24: - From version 2 (July 17 2006) the script uses the imageconvolution function in PHP
25: version >= 5.1, which improves the performance considerably.
26:
27: Unsharp masking is a traditional darkroom technique that has proven very suitable for
28: digital imaging. The principle of unsharp masking is to create a blurred copy of the image
29: and compare it to the underlying original. The difference in colour values
30: between the two images is greatest for the pixels near sharp edges. When this
31: difference is subtracted from the original image, the edges will be
32: accentuated.
33:
34: The Amount parameter simply says how much of the effect you want. 100 is 'normal'.
35: Radius is the radius of the blurring circle of the mask. 'Threshold' is the least
36: difference in colour values that is allowed between the original and the mask. In practice
37: this means that low-contrast areas of the picture are left unrendered whereas edges
38: are treated normally. This is good for pictures of e.g. skin or blue skies.
39:
40: Any suggenstions for improvement of the algorithm, expecially regarding the speed
41: and the roundoff errors in the Gaussian blur process, are welcome.
42: */
43:
44: class phpUnsharpMask {
45:
46: static function applyUnsharpMask(&$img, $amount, $radius, $threshold) {
47:
48: // $img is an image that is already created within php using
49: // imgcreatetruecolor. No url! $img must be a truecolor image.
50:
51: // Attempt to calibrate the parameters to Photoshop:
52: $amount = min($amount, 500) * 0.016;
53: $radius = abs(round(min(50, $radius) * 2)); // Only integers make sense.
54: $threshold = min(255, $threshold);
55: if ($radius == 0) {
56: return true;
57: }
58: $w = imagesx($img);
59: $h = imagesy($img);
60: $imgCanvas = imagecreatetruecolor($w, $h);
61: $imgBlur = imagecreatetruecolor($w, $h);
62:
63: // Gaussian blur matrix:
64: //
65: // 1 2 1
66: // 2 4 2
67: // 1 2 1
68: //
69: //////////////////////////////////////////////////
70:
71: if (function_exists('imageconvolution')) { // PHP >= 5.1
72: $matrix = array(
73: array(1, 2, 1),
74: array(2, 4, 2),
75: array(1, 2, 1)
76: );
77: imagecopy($imgBlur, $img, 0, 0, 0, 0, $w, $h);
78: imageconvolution($imgBlur, $matrix, 16, 0);
79:
80: } else {
81:
82: // Move copies of the image around one pixel at the time and merge them with weight
83: // according to the matrix. The same matrix is simply repeated for higher radii.
84: for ($i = 0; $i < $radius; $i++) {
85: imagecopy( $imgBlur, $img, 0, 0, 1, 0, $w - 1, $h); // left
86: imagecopymerge($imgBlur, $img, 1, 0, 0, 0, $w , $h, 50); // right
87: imagecopymerge($imgBlur, $img, 0, 0, 0, 0, $w , $h, 50); // center
88: imagecopy( $imgCanvas, $imgBlur, 0, 0, 0, 0, $w , $h);
89: imagecopymerge($imgBlur, $imgCanvas, 0, 0, 0, 1, $w , $h - 1, 33.33333); // up
90: imagecopymerge($imgBlur, $imgCanvas, 0, 1, 0, 0, $w , $h, 25); // down
91: }
92: }
93:
94: if ($threshold > 0){
95: // Calculate the difference between the blurred pixels and the original
96: // and set the pixels
97: for ($x = 0; $x < $w-1; $x++) { // each row
98: for ($y = 0; $y < $h; $y++) { // each pixel
99:
100: $rgbOrig = imagecolorat($img, $x, $y);
101: $rOrig = (($rgbOrig >> 16) & 0xFF);
102: $gOrig = (($rgbOrig >> 8) & 0xFF);
103: $bOrig = ($rgbOrig & 0xFF);
104:
105: $rgbBlur = imagecolorat($imgBlur, $x, $y);
106:
107: $rBlur = (($rgbBlur >> 16) & 0xFF);
108: $gBlur = (($rgbBlur >> 8) & 0xFF);
109: $bBlur = ($rgbBlur & 0xFF);
110:
111: // When the masked pixels differ less from the original
112: // than the threshold specifies, they are set to their original value.
113: $rNew = ((abs($rOrig - $rBlur) >= $threshold) ? max(0, min(255, ($amount * ($rOrig - $rBlur)) + $rOrig)) : $rOrig);
114: $gNew = ((abs($gOrig - $gBlur) >= $threshold) ? max(0, min(255, ($amount * ($gOrig - $gBlur)) + $gOrig)) : $gOrig);
115: $bNew = ((abs($bOrig - $bBlur) >= $threshold) ? max(0, min(255, ($amount * ($bOrig - $bBlur)) + $bOrig)) : $bOrig);
116:
117: if (($rOrig != $rNew) || ($gOrig != $gNew) || ($bOrig != $bNew)) {
118: $pixCol = imagecolorallocate($img, $rNew, $gNew, $bNew);
119: imagesetpixel($img, $x, $y, $pixCol);
120: }
121: }
122: }
123: } else {
124: for ($x = 0; $x < $w; $x++) { // each row
125: for ($y = 0; $y < $h; $y++) { // each pixel
126: $rgbOrig = imagecolorat($img, $x, $y);
127: $rOrig = (($rgbOrig >> 16) & 0xFF);
128: $gOrig = (($rgbOrig >> 8) & 0xFF);
129: $bOrig = ($rgbOrig & 0xFF);
130:
131: $rgbBlur = imagecolorat($imgBlur, $x, $y);
132:
133: $rBlur = (($rgbBlur >> 16) & 0xFF);
134: $gBlur = (($rgbBlur >> 8) & 0xFF);
135: $bBlur = ($rgbBlur & 0xFF);
136:
137: $rNew = min(255, max(0, ($amount * ($rOrig - $rBlur)) + $rOrig));
138: $gNew = min(255, max(0, ($amount * ($gOrig - $gBlur)) + $gOrig));
139: $bNew = min(255, max(0, ($amount * ($bOrig - $bBlur)) + $bOrig));
140: $rgbNew = ($rNew << 16) + ($gNew <<8) + $bNew;
141: imagesetpixel($img, $x, $y, $rgbNew);
142: }
143: }
144: }
145: imagedestroy($imgCanvas);
146: imagedestroy($imgBlur);
147: return true;
148: }
149: }
150: