note 79116 added to function.imagecolorat

As creamdog noted before, the alpha channel IS available from this function! (The manual should probably be updated to include this!) $rgba = imagecolorat($im,$x,$y); $alpha = ($rgba & 0x7F000000) >> 24; $alpha will then contain the TRANSPARENCY (NOT OPACITY) level. So 127, the max, would be completely transparent, and 0 would be completely opaque. Using this information, it is possible to write a dithering png-to-gif function like the completely working simple one below: <?php $im = imagecreatefrompng($pngRel); $transparentColor = imagecolorallocate($im, 0xfe, 0x3, 0xf4 ); $height = imagesy($im); $width = imagesx($im); for($x = 0; $x < $width; $x++){ for($y = 0; $y < $height; $y++) { $alpha = (imagecolorat($im,$x,$y) & 0x7F000000) >> 24; //DITHER! if ($alpha > 3 && ( $alpha >=127-3 || (rand(0,127))>=(127-$alpha) )){ imagesetpixel($im,$x,$y,$transparentColor); } } } imagecolortransparent($im, $transparentColor); imagegif($im, $gifRel);//save header("Content-type: image/gif"); readfile($gifRel); //pass thru to browser ?> ---- Server IP: 69.147.83.197 Probable Submitter: 63.229.78.26 ---- Manual Page -- http://www.php.net/manual/en/function.imagecolorat.php Edit -- https://master.php.net/note/edit/79116 Del: integrated -- https://master.php.net/note/delete/79116/integrated Del: useless -- https://master.php.net/note/delete/79116/useless Del: bad code -- https://master.php.net/note/delete/79116/bad+code Del: spam -- https://master.php.net/note/delete/79116/spam Del: non-english -- https://master.php.net/note/delete/79116/non-english Del: in docs -- https://master.php.net/note/delete/79116/in+docs Del: other reasons-- https://master.php.net/note/delete/79116 Reject -- https://master.php.net/note/reject/79116 Search -- https://master.php.net/manage/user-notes.php