<?php
// this will only handle alpha-transparency in the source image
// transparency in the destination image where it is overlayed by the source will be lost...
Function imagecopymerge_alpha($dst_im, $src_im, $dst_x, $dst_y, $src_x, $src_y, $src_w, $src_h, $pct) {
// lifted from Sina Salek’s comments on http://us.php.net/manual/en/function.imagecopymerge.php
// modified adaption by SoftMoon WebWare
/**
* PNG ALPHA CHANNEL SUPPORT for imagecopymerge();
* by Sina Salek
*
* Bugfix by Ralph Voigt (bug which causes it
* to work only for $src_x = $src_y = 0.
* Also, inverting opacity is not necessary.)
* 08-JAN-2011
*
**/
if (100==$pct)
imagecopy($dst_im, $src_im, $dst_x, $dst_y, $src_x, $src_y, $src_w, $src_h);
else {
// creating a cut resource
$cut = imagecreatetruecolor($src_w, $src_h);
// copying relevant section from background to the cut resource
imagecopy($cut, $dst_im, 0, 0, $dst_x, $dst_y, $src_w, $src_h, 100);
// copying relevant section from watermark to the cut resource
imagecopy($dupl, $src_im, 0, 0, $src_x, $src_y, $src_w, $src_h);
// insert cut resource to destination image
imagecopymerge($dst_im, $dupl, $dst_x, $dst_y, 0, 0, $src_w, $src_h, $pct);
imagedestroy($dupl); } }
// this will handle alpha-transparency in both the source and destination images
Function imagecopymerge_alpha2($dst_im, $src_im, $dst_x, $dst_y, $src_x, $src_y, $src_w, $src_h, $pct) {
$pct=round(127-($pct/100)*127); // 0 <= $pct <= 100 convert opacity percentage to alpha-channel value
for ($x=0; $x<$src_w; $x++) { for ($y=0; $y<$src_h; $y++) {
$src_pixel=imagecolorsforindex($src_im, imagecolorat($src_im, $x, $y));
$dst_pixel=imagecolorsforindex($dst_im, imagecolorat($dst_im, $dst_x+$x, $dst_y+$y));
$pixel=imagecolorallocatealpha($dst_im,
$src_pixel['red'],
$src_pixel['green'],
$src_pixel['blue'],
$tf=min($src_pixel['alpha'] + $pct, 127));
imagealphablending($dst_im, TRUE);
imagesetpixel($dst_im, $dst_x+$x, $dst_y+$y, $pixel);
imagecolordeallocate($dst_im, $pixel);
$int_pixel=imagecolorsforindex($dst_im, imagecolorat($dst_im, $dst_x+$x, $dst_y+$y));
$pixel=imagecolorallocatealpha($dst_im,
$int_pixel['red'],
$int_pixel['green'],
$int_pixel['blue'],
$dst_pixel['alpha']*$tf/127 );
imagealphablending($dst_im, FALSE);
imagesetpixel($dst_im, $dst_x+$x, $dst_y+$y, $pixel);
imagecolordeallocate($dst_im, $pixel); } } }
?>
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