162 lines
6.9 KiB
PHP
162 lines
6.9 KiB
PHP
<?php
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//////////////////////////////////////////////////////////////
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//// ////
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//// p h p U n s h a r p M a s k ////
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//// ////
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//// Unsharp mask algorithm by Torstein Hønsi 2003. ////
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//// thoensi_at_netcom_dot_no ////
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//// Please leave this notice. ////
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//// ////
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//////////////////////////////////////////////////////////////
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/// From: http://vikjavev.no/hovudsida/umtestside.php //
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// //
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// Reformatted by James Heinrich <info@silisoftware.com> //
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// for use in phpThumb() on 3 February 2003. //
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// //
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// phpThumb() is found at http://phpthumb.sourceforge.net ///
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//////////////////////////////////////////////////////////////
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/*
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WARNING! Due to a known bug in PHP 4.3.2 this script is not working well in this version.
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The sharpened images get too dark. The bug is fixed in version 4.3.3.
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Unsharp masking is a traditional darkroom technique that has proven very suitable for
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digital imaging. The principle of unsharp masking is to create a blurred copy of the image
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and compare it to the underlying original. The difference in colour values
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between the two images is greatest for the pixels near sharp edges. When this
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difference is subtracted from the original image, the edges will be
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accentuated.
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The Amount parameter simply says how much of the effect you want. 100 is 'normal'.
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Radius is the radius of the blurring circle of the mask. 'Threshold' is the least
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difference in colour values that is allowed between the original and the mask. In practice
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this means that low-contrast areas of the picture are left unrendered whereas edges
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are treated normally. This is good for pictures of e.g. skin or blue skies.
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Any suggenstions for improvement of the algorithm, expecially regarding the speed
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and the roundoff errors in the Gaussian blur process, are welcome.
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*/
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class phpUnsharpMask {
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function applyUnsharpMask(&$img, $amount, $radius, $threshold) {
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// $img is an image that is already created within php using
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// imgcreatetruecolor. No url! $img must be a truecolor image.
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// Attempt to calibrate the parameters to Photoshop:
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$amount = min($amount, 500);
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$amount = $amount * 0.016;
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if ($amount == 0) {
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return true;
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}
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$radius = min($radius, 50);
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$radius = $radius * 2;
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$threshold = min($threshold, 255);
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$radius = abs(round($radius)); // Only integers make sense.
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if ($radius == 0) {
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return true;
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}
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$w = ImageSX($img);
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$h = ImageSY($img);
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$imgCanvas = ImageCreateTrueColor($w, $h);
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$imgCanvas2 = ImageCreateTrueColor($w, $h);
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ImageCopy($imgCanvas, $img, 0, 0, 0, 0, $w, $h);
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ImageCopy($imgCanvas2, $img, 0, 0, 0, 0, $w, $h);
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$builtinFilterSucceeded = false;
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if ($radius == 1) {
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if (phpthumb_functions::version_compare_replacement(phpversion(), '5.0.0', '>=') && phpthumb_functions::gd_is_bundled()) {
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if (ImageFilter($imgCanvas, IMG_FILTER_GAUSSIAN_BLUR) && ImageFilter($imgCanvas2, IMG_FILTER_GAUSSIAN_BLUR)) {
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$builtinFilterSucceeded = true;
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}
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}
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}
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if (!$builtinFilterSucceeded) {
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$imgBlur = ImageCreateTrueColor($w, $h);
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$imgBlur2 = ImageCreateTrueColor($w, $h);
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///////////////////////////
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//
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// Gaussian blur matrix:
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// 1 2 1
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// 2 4 2
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// 1 2 1
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//
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///////////////////////////
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// Move copies of the image around one pixel at the time and merge them with weight
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// according to the matrix. The same matrix is simply repeated for higher radii.
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for ($i = 0; $i < $radius; $i++) {
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ImageCopy ($imgBlur, $imgCanvas, 0, 0, 1, 1, $w - 1, $h - 1); // up left
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ImageCopyMerge($imgBlur, $imgCanvas, 1, 1, 0, 0, $w, $h, 50); // down right
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ImageCopyMerge($imgBlur, $imgCanvas, 0, 1, 1, 0, $w - 1, $h, 33.33333); // down left
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ImageCopyMerge($imgBlur, $imgCanvas, 1, 0, 0, 1, $w, $h - 1, 25); // up right
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ImageCopyMerge($imgBlur, $imgCanvas, 0, 0, 1, 0, $w - 1, $h, 33.33333); // left
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ImageCopyMerge($imgBlur, $imgCanvas, 1, 0, 0, 0, $w, $h, 25); // right
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ImageCopyMerge($imgBlur, $imgCanvas, 0, 0, 0, 1, $w, $h - 1, 20 ); // up
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ImageCopyMerge($imgBlur, $imgCanvas, 0, 1, 0, 0, $w, $h, 16.666667); // down
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ImageCopyMerge($imgBlur, $imgCanvas, 0, 0, 0, 0, $w, $h, 50); // center
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ImageCopy ($imgCanvas, $imgBlur, 0, 0, 0, 0, $w, $h);
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// During the loop above the blurred copy darkens, possibly due to a roundoff
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// error. Therefore the sharp picture has to go through the same loop to
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// produce a similar image for comparison. This is not a good thing, as processing
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// time increases heavily.
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ImageCopy ($imgBlur2, $imgCanvas2, 0, 0, 0, 0, $w, $h);
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ImageCopyMerge($imgBlur2, $imgCanvas2, 0, 0, 0, 0, $w, $h, 50);
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ImageCopyMerge($imgBlur2, $imgCanvas2, 0, 0, 0, 0, $w, $h, 33.33333);
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ImageCopyMerge($imgBlur2, $imgCanvas2, 0, 0, 0, 0, $w, $h, 25);
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ImageCopyMerge($imgBlur2, $imgCanvas2, 0, 0, 0, 0, $w, $h, 33.33333);
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ImageCopyMerge($imgBlur2, $imgCanvas2, 0, 0, 0, 0, $w, $h, 25);
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ImageCopyMerge($imgBlur2, $imgCanvas2, 0, 0, 0, 0, $w, $h, 20 );
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ImageCopyMerge($imgBlur2, $imgCanvas2, 0, 0, 0, 0, $w, $h, 16.666667);
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ImageCopyMerge($imgBlur2, $imgCanvas2, 0, 0, 0, 0, $w, $h, 50);
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ImageCopy ($imgCanvas2, $imgBlur2, 0, 0, 0, 0, $w, $h);
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}
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ImageDestroy($imgBlur);
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ImageDestroy($imgBlur2);
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}
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// Calculate the difference between the blurred pixels and the original
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// and set the pixels
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for ($x = 0; $x < $w; $x++) { // each row
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for ($y = 0; $y < $h; $y++) { // each pixel
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$rgbOrig = ImageColorAt($imgCanvas2, $x, $y);
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$rOrig = (($rgbOrig >> 16) & 0xFF);
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$gOrig = (($rgbOrig >> 8) & 0xFF);
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$bOrig = ($rgbOrig & 0xFF);
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$rgbBlur = ImageColorAt($imgCanvas, $x, $y);
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$rBlur = (($rgbBlur >> 16) & 0xFF);
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$gBlur = (($rgbBlur >> 8) & 0xFF);
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$bBlur = ($rgbBlur & 0xFF);
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// When the masked pixels differ less from the original
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// than the threshold specifies, they are set to their original value.
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$rNew = (abs($rOrig - $rBlur) >= $threshold) ? max(0, min(255, ($amount * ($rOrig - $rBlur)) + $rOrig)) : $rOrig;
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$gNew = (abs($gOrig - $gBlur) >= $threshold) ? max(0, min(255, ($amount * ($gOrig - $gBlur)) + $gOrig)) : $gOrig;
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$bNew = (abs($bOrig - $bBlur) >= $threshold) ? max(0, min(255, ($amount * ($bOrig - $bBlur)) + $bOrig)) : $bOrig;
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if (($rOrig != $rNew) || ($gOrig != $gNew) || ($bOrig != $bNew)) {
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$pixCol = ImageColorAllocate($img, $rNew, $gNew, $bNew);
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ImageSetPixel($img, $x, $y, $pixCol);
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}
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}
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}
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ImageDestroy($imgCanvas);
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ImageDestroy($imgCanvas2);
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return true;
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}
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}
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?>
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