ID: 47946
User updated by: jcolby at acsol dot net
Reported By: jcolby at acsol dot net
Status: Open
Bug Type: GD related
Operating System: openSuse, CentOS, FreeBSD
PHP Version: 5.2.9
New Comment:
Missing function from test case:
function array_flatten($array) {
(array)$tempArray = array();
foreach ( $array as $value ) {
if ( is_array($value) ) {
$tempArray = array_merge($tempArray, array_flatten($value));
} else {
$tempArray[] = $value;
}
}
return $tempArray;
}
Previous Comments:
------------------------------------------------------------------------
[2009-04-10 16:26:01] jcolby at acsol dot net
Description:
------------
When using imageconvolution on an image containing alpha, the
background color on the resource image will be replaced with opaque
black regardless of any alpha or background settings. This is because of
the gdimagecopy internal to the function without the proper savealpha
flags being set & no transparent image fill after gdimagecreatetruecolor
is used inside the function.
This is similar to bug #34992 but I've had a chance to break it open
and actually fix it.
This affects all versions of php 5, up to the latest 5.2.9 stable
build, and I wouldn't doubt it currently affects 6 as well.
Now, I managed to fix it in my own build, but I don't know how to get
it advanced from there. This is not my realm of experience, I just had
to repair it.
Patch: php-5.2.9\ext\gd\libgd\gd.c
Add in var initialization:
/* patch */
gdImagePtr srctrans;
/* patch */
Add after "srcback = gdImageCreateTrueColor..."
/* patch */
srcback->saveAlphaFlag = 1;
srctrans = gdImageColorAllocateAlpha(srcback, 0, 0, 0, 127);
gdImageFill(srcback, 0, 0, srctrans);
/* end patch */
Thats all it requires.
Reproduce code:
---------------
<?php
function makeFilter($resource, $matrix, $offset=1.0) {
global $$resource;
(float)$divisor = array_sum(array_flatten($matrix));
if ($divisor == 0) {
$divisor = .01;
}
return imageconvolution($resource, $matrix, $divisor, $offset)
? true : false;
}
$edgeMatrix = array(array(1, 0, 1), array(0, 5, 0), array(1, 0, 1));
$file = "images/anypngwithalpha.png"; // path to png image
$im = imagecreatefrompng($file); // open image
imagesavealpha($im, true);
makeFilter($im, $edgeMatrix);
header('Content-type: image/png');
imagepng($im);
imagedestroy($im);
?>
Expected result:
----------------
Convolutionmatrix should apply to all opaque or semi opaque pixels, and
background should remain unchanged.
Actual result:
--------------
Convolutionmatrix applies to all opaque and semi opaque pixels,
background reverts to solid opaque black regardless of any external
settings.
------------------------------------------------------------------------
--
Edit this bug report at http://bugs.php.net/?id=47946&edit=1
