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/*
New:
- In version 2.1 (February 26 2007) Tom Bishop has done some important speed enhancements.
- From version 2 (July 17 2006) the script uses the `imageconvolution()` function in PHP
version >= 5.1, which improves the performance considerably.
Unsharp masking is a traditional darkroom technique that has proven very suitable for
digital imaging. The principle of unsharp masking is to create a blurred copy of the image
and compare it to the underlying original. The difference in colour values
between the two images is greatest for the pixels near sharp edges. When this
difference is subtracted from the original image, the edges will be
accentuated.
The Amount parameter simply says how much of the effect you want. 100 is 'normal'.
Radius is the radius of the blurring circle of the mask. 'Threshold' is the least
difference in colour values that is allowed between the original and the mask. In practice
this means that low-contrast areas of the picture are left un-rendered whereas edges
are treated normally. This is good for pictures of e.g. skin or blue skies.
Any suggestions for improvement of the algorithm, especially regarding the speed
and the round off errors in the Gaussian blur process, are welcome.
*/
namespace MvcCore\Ext\Tools\Images\Gds;
class UnsharpMask {
////////////////////////////////////////////////////////////////////////////////////////////////
////
//// Unsharp Mask for PHP - version 2.1.1
////
//// Unsharp mask algorithm by Torstein Hønsi 2003-07.
//// http://vikjavev.no/computing/ump.php
//// thoensi_at_netcom_dot_no.
//// Please leave this notice.
////
///////////////////////////////////////////////////////////////////////////////////////////////
/**
* @param resource $img Gd resource reference
* @param int $amount typically 50 - 200, min 0, max 500
* @param float $radius typically 0.5 - 1, min 0, max 50
* @param int $threshold typically 0 - 5, min 0, max 255
* @return void
*/
public static function Process ($img, $amount, $radius, $threshold) {
// $img is an image that is already created within php using
// imgcreatetruecolor. No url! $img must be a truecolor image.
// Attempt to calibrate the parameters to Photoshop:
if ($amount > 500) $amount = 500;
$amount = $amount * 0.016;
if ($radius > 50) $radius = 50;
$radius = $radius * 2;
if ($threshold > 255) $threshold = 255;
$radius = abs(round($radius)); // Only integers make sense.
if ($radius == 0) return $img;
$w = imagesx($img);
$h = imagesy($img);
$imgCanvas = imagecreatetruecolor($w, $h);
$imgBlur = imagecreatetruecolor($w, $h);
// Gaussian blur matrix:
//
// 1 2 1
// 2 4 2
// 1 2 1
//
//////////////////////////////////////////////////
if (function_exists('imageconvolution')) { // PHP >= 5.1
$matrix = [
[ 1, 2, 1 ],
[ 2, 4, 2 ],
[ 1, 2, 1 ]
];
imagecopy ($imgBlur, $img, 0, 0, 0, 0, $w, $h);
imageconvolution($imgBlur, $matrix, 16, 0);
} else {
// Move copies of the image around one pixel at the time and merge them with weight
// according to the matrix. The same matrix is simply repeated for higher radii.
for ($i = 0; $i < $radius; $i++) {
imagecopy ($imgBlur, $img, 0, 0, 1, 0, $w - 1, $h); // left
imagecopymerge ($imgBlur, $img, 1, 0, 0, 0, $w, $h, 50); // right
imagecopymerge ($imgBlur, $img, 0, 0, 0, 0, $w, $h, 50); // center
imagecopy ($imgCanvas, $imgBlur, 0, 0, 0, 0, $w, $h);
imagecopymerge ($imgBlur, $imgCanvas, 0, 0, 0, 1, $w, $h - 1, 33.33333 ); // up
imagecopymerge ($imgBlur, $imgCanvas, 0, 1, 0, 0, $w, $h, 25); // down
}
}
if ($threshold>0) {
// Calculate the difference between the blurred pixels and the original
// and set the pixels
for ($x = 0; $x < $w-1; $x++) { // each row
for ($y = 0; $y < $h; $y++) { // each pixel
$rgbOrig = ImageColorAt($img, $x, $y);
$rOrig = (($rgbOrig >> 16) & 0xFF);
$gOrig = (($rgbOrig >> 8) & 0xFF);
$bOrig = ($rgbOrig & 0xFF);
$rgbBlur = ImageColorAt($imgBlur, $x, $y);
$rBlur = (($rgbBlur >> 16) & 0xFF);
$gBlur = (($rgbBlur >> 8) & 0xFF);
$bBlur = ($rgbBlur & 0xFF);
// When the masked pixels differ less from the original
// than the threshold specifies, they are set to their original value.
$rNew = (abs($rOrig - $rBlur) >= $threshold)
? max(0, min(255, ($amount * ($rOrig - $rBlur)) + $rOrig))
: $rOrig;
$gNew = (abs($gOrig - $gBlur) >= $threshold)
? max(0, min(255, ($amount * ($gOrig - $gBlur)) + $gOrig))
: $gOrig;
$bNew = (abs($bOrig - $bBlur) >= $threshold)
? max(0, min(255, ($amount * ($bOrig - $bBlur)) + $bOrig))
: $bOrig;
if (($rOrig != $rNew) || ($gOrig != $gNew) || ($bOrig != $bNew)) {
$pixCol = ImageColorAllocate($img, $rNew, $gNew, $bNew);
ImageSetPixel($img, $x, $y, $pixCol);
}
}
}
} else {
for ($x = 0; $x < $w; $x++) { // each row
for ($y = 0; $y < $h; $y++) { // each pixel
$rgbOrig = ImageColorAt($img, $x, $y);
$rOrig = (($rgbOrig >> 16) & 0xFF);
$gOrig = (($rgbOrig >> 8) & 0xFF);
$bOrig = ($rgbOrig & 0xFF);
$rgbBlur = ImageColorAt($imgBlur, $x, $y);
$rBlur = (($rgbBlur >> 16) & 0xFF);
$gBlur = (($rgbBlur >> 8) & 0xFF);
$bBlur = ($rgbBlur & 0xFF);
$rNew = ($amount * ($rOrig - $rBlur)) + $rOrig;
if($rNew>255){$rNew=255;}
elseif($rNew<0){$rNew=0;}
$gNew = ($amount * ($gOrig - $gBlur)) + $gOrig;
if($gNew>255){$gNew=255;}
elseif($gNew<0){$gNew=0;}
$bNew = ($amount * ($bOrig - $bBlur)) + $bOrig;
if($bNew>255){$bNew=255;}
elseif($bNew<0){$bNew=0;}
$rgbNew = ($rNew << 16) + ($gNew <<8) + $bNew;
ImageSetPixel($img, $x, $y, $rgbNew);
}
}
}
imagedestroy($imgCanvas);
imagedestroy($imgBlur);
}
}