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copied!<p>I like your script, good idea to remove extra colour information when the pixel is totally transparent. I should point out just a small error (IMO) though if anyone wants to use this method.</p> <pre><code>$color = imagecolorsforindex( $source, imagecolorat( $source, $x, $y ) ); </code></pre> <p>should be</p> <pre><code>$color = imagecolorsforindex( $picture, imagecolorat( $picture, $x, $y ) ); </code></pre> <p>also I'm not 100% sure why you're checking rgb values here if the pixel is 100% transparent</p> <pre><code>if(($alpha['red'] == 0) && ($alpha['green'] == 0) && ($alpha['blue'] == 0) && ($alpha['alpha'] == 0)) ... </code></pre> <p>and I'm not sure alpha blending from the mask file would work well with your method, as its only used when rgba values all equal 0.</p> <p>Jules's script is pretty good too, though it expects the mask to be a grey scale representation of a mask (which is pretty common practice). </p> <p>In Matt's query he was after a script that grabs just the alpha transparency from an existing image and applies it to another image. Here's a simple mod of Jules's script just to grab the alpha from the mask image, and preserve the alpha of the source image.</p> <pre><code><?php // Load source and mask $source = imagecreatefrompng( '1.png' ); $mask = imagecreatefrompng( '2.png' ); // Apply mask to source imagealphamask( $source, $mask ); // Output header( "Content-type: image/png"); imagepng( $source ); function imagealphamask( &$picture, $mask ) { // Get sizes and set up new picture $xSize = imagesx( $picture ); $ySize = imagesy( $picture ); $newPicture = imagecreatetruecolor( $xSize, $ySize ); imagesavealpha( $newPicture, true ); imagefill( $newPicture, 0, 0, imagecolorallocatealpha( $newPicture, 0, 0, 0, 127 ) ); // Resize mask if necessary if( $xSize != imagesx( $mask ) || $ySize != imagesy( $mask ) ) { $tempPic = imagecreatetruecolor( $xSize, $ySize ); imagecopyresampled( $tempPic, $mask, 0, 0, 0, 0, $xSize, $ySize, imagesx( $mask ), imagesy( $mask ) ); imagedestroy( $mask ); $mask = $tempPic; } // Perform pixel-based alpha map application for( $x = 0; $x < $xSize; $x++ ) { for( $y = 0; $y < $ySize; $y++ ) { $alpha = imagecolorsforindex( $mask, imagecolorat( $mask, $x, $y ) ); //small mod to extract alpha, if using a black(transparent) and white //mask file instead change the following line back to Jules's original: //$alpha = 127 - floor($alpha['red'] / 2); //or a white(transparent) and black mask file: //$alpha = floor($alpha['red'] / 2); $alpha = $alpha['alpha']; $color = imagecolorsforindex( $picture, imagecolorat( $picture, $x, $y ) ); //preserve alpha by comparing the two values if ($color['alpha'] > $alpha) $alpha = $color['alpha']; //kill data for fully transparent pixels if ($alpha == 127) { $color['red'] = 0; $color['blue'] = 0; $color['green'] = 0; } imagesetpixel( $newPicture, $x, $y, imagecolorallocatealpha( $newPicture, $color[ 'red' ], $color[ 'green' ], $color[ 'blue' ], $alpha ) ); } } // Copy back to original picture imagedestroy( $picture ); $picture = $newPicture; } ?> </code></pre>

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