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

ID: 40158 Updated by: pajoye@php.net Reported By: henus at mail dot ru -Status: Open +Status: Feedback Bug Type: GD related Operating System: Windows XP PHP Version: 5.2.0 Assigned To: pajoye New Comment: 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. Previous Comments: ------------------------------------------------------------------------ [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 ) ------------------------------------------------------------------------ [2007-01-18 15:22:49] pajoye@php.net Can you provide an image to show what you expect? I did not check your script but having an image will help to really understand what you are trying to achieve. By the way, filters work only with truecolor images, allocate will never fail. ------------------------------------------------------------------------ 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