#40158 [Fbk]: Artifact left on transparent pngs using image filters

ID: 40158 Updated by: pajoye@php.net Reported By: henus at mail dot ru Status: Feedback Bug Type: GD related Operating System: Windows XP PHP Version: 5.2.0 Assigned To: pajoye New Comment: (rgba(255,0,0,xxx)) should have been (rgba(0,0,255,xxx)) but you noticed it :) Previous Comments: ------------------------------------------------------------------------ [2007-01-18 18:51:04] pajoye@php.net An absolute black image is not what you should expect. imagefilter($mask, IMG_FILTER_COLORIZE, -255, -255, 0); will replace the white color with blue (you remove all components but the blue): http://blog.thepimp.net/misc/bug40158_filtered_mask.png imagecopy($imagemain, $mask, 0, 0, 0, 0, $imagewidth, $imageheight); will copy it over the $imagemain, the border of the quadrant will be blended over black: http://blog.thepimp.net/misc/bug40158_result.png Each pixel in your circle are rgb(255,255,255) with some alpha value in the edges (and only in the edges). You are substracting 255 to the R and G component, the result is blue. Now, take a look at this image: http://blog.thepimp.net/misc/bug40158_correct_filtered_mask.png It is what you are expecting (if I understand correctly your problem). The edges of the circle have a blue color with various alpha values (rgba(255,0,0,xxx)). You can reproduce it by disabling the alpha blending mode in the mask image (imagealphablending($mask, false); ). The alpha component will be kept and stored in the image instead of being used as a blending value. Let me know if that solves your problem. By the way, COLORIZE uses gdImageColor. The lines you are referring to are in the contrast function. ------------------------------------------------------------------------ [2007-01-18 18:32:16] henus at mail dot ru i expect absolutely black image like http://www.fort-ross.ru/henus/gd/result_correct.png instead of http://www.fort-ross.ru/henus/gd/result_incorrect.png i use colorizing by black for clearness. ------------------------------------------------------------------------ [2007-01-18 18:11:31] henus at mail dot ru correction fo my previous post about php-5.2.0\ext\gd\libgd\gd.c Lines 3682-3688: new_pxl = gdImageColorAllocateAlpha(src, (int)r, (int)g, (int)b, a); if (new_pxl == -1) { new_pxl = gdImageColorClosestAlpha(src, (int)r, (int)g, (int)b, a); } if ((y >= 0) && (y < src->sy)) { gdImageSetPixel (src, x, y, new_pxl); in gdImageSetPixel src should be absolutely transparent, with alpha=127 differently it mix colors. ------------------------------------------------------------------------ [2007-01-18 18:09:31] pajoye@php.net Please provide an *image* showing what you expect. ------------------------------------------------------------------------ [2007-01-18 17:56:25] henus at mail dot ru i create black image and overlay it by colorized white-truecolor-png24-image ( http://fort-ross.ru/henus/gd/mask.png ) the result of colorize like: imagefilter($mask, IMG_FILTER_COLORIZE, -255, -255, -255); is image: http://www.fort-ross.ru/henus/gd/result_incorrect.png which contain artefacts... also, the result of such script ( http://fort-ross.ru/henus/gd/demo2.phps ) is: is truecolor - 1 before - Array ( [red] => 255 [green] => 255 [blue] => 255 [alpha] => 63 ) wrong result, using filter - Array ( [red] => 126 [green] => 126 [blue] => 126 [alpha] => 31 ) wrong result, using imagecolorallocatealpha and imagesetpixel - Array ( [red] => 126 [green] => 126 [blue] => 126 [alpha] => 31 ) correct result, using imagefill, imagecolorallocatealpha and imagesetpixel - Array ( [red] => 0 [green] => 0 [blue] => 0 [alpha] => 63 ) I.e. colorizing pixel ( [red] => 255 [green] => 255 [blue] => 255 [alpha] => 63 ) to black should be with ( [red] => 0 [green] => 0 [blue] => 0 [alpha] => 63 ), not ( [red] => 126 [green] => 126 [blue] => 126 [alpha] => 31 ) ------------------------------------------------------------------------ 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/40158 -- Edit this bug report at http://bugs.php.net/?id=40158&edit=1