#45030 [Opn->Fbk]: Destination image alpah channle noise when using imagecopyresampled

ID: 45030 Updated by: pajoye@php.net Reported By: lieyang at yahoo dot com -Status: Open +Status: Feedback Bug Type: GD related Operating System: x86_64 GNU/Linux Kernel 2.6.9-4 PHP Version: 5.2.6 Assigned To: pajoye New Comment: The 56x56 image looks perfectly fine to me. I also checked the alpha values for the translucent areas and they look fine too (full translucent when they are not near the star anti aliased pixels, as expected). To see how is the alpha channel in the result image, please look at this zoomed version of the alpha channel only: http://pierre.libgd.org/bugs/45030_alpha_only.png 100% black means opaque and the gray squares are only to show a background (what would be behind the image). As you can see, there is no noise in the transparent areas. Are you sure that there is not a bug in the Motorola display system? Maybe it does not support semi transparent pixels. Previous Comments: ------------------------------------------------------------------------ [2008-05-18 03:51:39] lieyang at yahoo dot com Here are my test source image (png 90x90): http://tinyurl.com/65tdtm Resized to 56x56 with noise in alpha channel: http://tinyurl.com/6yold7 ------------------------------------------------------------------------ [2008-05-18 03:41:50] lieyang at yahoo dot com Please try the following with different image sizes and you will see that the alpha channel has noise. (I have two original before and after images but can not find the link to upload them as attachments) $imageSrc = imagecreatetruecolor(90, 90); imagealphablending($imageSrc, false); imagesavealpha($imageSrc, true); $color = imagecolorallocatealpha($imageSrc, 0, 0, 0, 127); imagefill($imageSrc, 0, 0, $color); $imageDst = imagecreatetruecolor(56, 56); imagealphablending($imageDst, false); imagesavealpha($imageDst, true); imagecopyresampled($imageDst,$imageSrc, 0, 0, 0, 0, 56, 56, 90, 90); header('Content-type: image/png'); imagepng($imageDst); ------------------------------------------------------------------------ [2008-05-17 23:11:41] rasmus@php.net We need a better reproducible example here, including the source image. When the source image has a perfect alpha channel, I see no noise. Try this: $imageSrc = imagecreatetruecolor(500, 500); imagealphablending($imageSrc, false); imagesavealpha($imageSrc, true); $color = imagecolorallocatealpha($imageSrc, 0, 0, 0, 127); imagefill($imageSrc, 0, 0, $color); $imageDst = imagecreatetruecolor(50, 50); imagealphablending($imageDst, false); imagesavealpha($imageDst, true); imagecopyresampled($imageDst,$imageSrc, 0, 0, 0, 0, 50, 50, 500, 500); header('Content-type: image/png'); imagepng($imageDst); ------------------------------------------------------------------------ [2008-05-17 22:52:00] pajoye@php.net In fact yes, I need the source image (what you have in $imageData). Sorry for the double posts. ------------------------------------------------------------------------ [2008-05-17 22:48:55] pajoye@php.net no need for src images :-) ------------------------------------------------------------------------ The remainder of the comments for this report are too long. To view the rest of the comments, please view the bug report online at http://bugs.php.net/45030 -- Edit this bug report at http://bugs.php.net/?id=45030&edit=1