ID: 40572
User updated by: seth at pricepages dot org
Reported By: seth at pricepages dot org
-Status: Feedback
+Status: Open
Bug Type: GD related
Operating System: Mac 10.4
PHP Version: 5.2.1
Assigned To: pajoye
New Comment:
Well, I ran the following code against the newly released C
library, and things seem to work as expected. GD 2.0.33 seg
faults for some reason, but 2.0.34 fixes that. So, the bug
will be fixed when you sync with PHP's code?
gdImagePtr img;
int trans, pTrans;
FILE *fp;
img = gdImageCreateTrueColor(100, 100);
gdImageAlphaBlending(img, 1);
trans = gdImageColorResolveAlpha(img,255,0,0, 127);
gdImageFill(img, 0,0, trans);
pTrans = gdImageColorResolveAlpha(img, 0,0,0, 64);
gdImageFilledRectangle(img, 10, 10, 50, 50, pTrans);
gdImageAlphaBlending(img, 0);
gdImageSaveAlpha(img,1);
fp = fopen("test.png", "w");
gdImagePng(img, fp);
fclose(fp);
gdImageDestroy(img);
Previous Comments:
------------------------------------------------------------------------
[2007-02-21 10:03:06] [EMAIL PROTECTED]
imagefill does not care about alpha blending but when you use a tiled
color (as it is actually an image/pattern filling).
"$trans = imagecolorresolvealpha($img,255,0,0, 127);"
Will always fill the area with red and a 100% transparent alpha.
"imagealphablending($img, true);" enables the blending mode. Set it to
false will store the alpha in the image.
You set it to true, that's why you get a "red/black" rectangle instead
of a gray semi transparent area.
However I agree that the behavior is not user friendly. The GD 2.0.34
behaves differently in a more logic way when the dst pixel is either
fully transparent or opaque.
OS X Fink already have 2.0.34, you can try to compile php against it.
Or you can see the different implementation in the GD sources (function
gdAlphaBlend):
http://cvs.php.net/viewvc.cgi/gd/libgd/gd.c
I will try to sync php gdAlphaBlend as soon as possible. I have to
check that it will not break BC in one way or another (I do not think
it will, but still need to test).
Do you get what you expect using the 2.0.34's gdAlphaBlend?
------------------------------------------------------------------------
[2007-02-21 05:01:04] seth at pricepages dot org
Description:
------------
I am filling the background of an image with a transparent red
(it shouldn't have an effect on the rest of the drawing). Over
it, I'm drawing a black, semi-transparent, square.
Reproduce code:
---------------
$img = imagecreatetruecolor(100, 100);
imagealphablending($img, true);
$trans = imagecolorresolvealpha($img,255,0,0, 127);
imagefill($img, 0,0, $trans);
$pTrans = imagecolorresolvealpha($img, 0,0,0, 64);
imagefilledrectangle($img, 10, 10, 50, 50, $pTrans);
imagealphablending($img, false);
imagesavealpha($img,true);
header('Content-Type: image/png');
imagepng($img);
Expected result:
----------------
I would expect the resulting image to be 100% transparent,
except for a grey, 50% transparent square.
Actual result:
--------------
Instead, the black is mixed with the red to form a dark-red
semi-transparent square. The red color should not be there,
because it was 100% transparent.
------------------------------------------------------------------------
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Edit this bug report at http://bugs.php.net/?id=40572&edit=1
