note 48355 added to function.imagecopy

This function will put a truecolor png with transparency over a custom color backgorund. The image will be gracefully blended with the background color using the alpha channel for each color. In real world we'd just mix foreground and backgorund colors looking at their percentages (i.e. 20% of background + 80% of foreground) Here we have to calculate this for each r, g and b value of each color, and we have to use 127 instead of 100, because alpha channel goes from 0 to 127. Try it on a color-to-transparent gradient! <?php function pngcolorizealpha($file, $color) { /* Function: pngcolorizealpha Author: CoD (cod at crescentofdarkness dot cjb dot net) Summary: Blends a truecolor png image with a coloured background using alpha channel Input: -------------------------- $file - string - path to the png image $color- string - color in hex notation, without the # Output: -------------------------- a png image */ // first of all let's convert the background color $background = array( 'red' => hexdec(substr($color,0,2)), 'green' => hexdec(substr($color,2,2)), 'blue' => hexdec(substr($color,4,2)) ); $im1 = imagecreatefrompng($file) or die('Cannot Initialize new GD image stream'); $im2 = imagecreatetruecolor(imagesx($im1), imagesy($im1)); $col1 = imagecolorallocate($im2, $background['red'], $background['green'], $background['blue']); imagefill($im2,0,0,$col1); // for each color in the original png for ($i=0; $i< imagecolorstotal($im1); $i++) { // find r,g,b and alpha value $foreground = imagecolorsforindex($im1, $i); // blend fore and back colors using alpha value $r = (($foreground['red'] / 127) * (127 - $foreground['alpha'])) + (($background['red'] / 127)* $foreground['alpha']); $g = (($foreground['green'] / 127) * (127 - $foreground['alpha'])) + (($background['green'] / 127)* $foreground['alpha']); $b = (($foreground['blue'] / 127) * (127 - $foreground['alpha'])) + (($background['blue'] / 127)* $foreground['alpha']); // allocate this new color in the destination image imagecolorallocate($im2, $r,$g,$b); } imagecopy($im2, $im1, 0, 0, 0, 0, imagesx($im1), imagesy($im1)); header ("Content-type: image/png"); imagepng($im2); imagedestroy($im1); imagedestroy($im2); } ?> ---- Manual Page -- http://www.php.net/manual/en/function.imagecopy.php Edit -- http://master.php.net/manage/user-notes.php?action=edit+48355 Delete -- http://master.php.net/manage/user-notes.php?action=delete+48355&report=yes Reason: bad code -- http://master.php.net/manage/user-notes.php?action=delete+48355&report=yes&reason=bad+code Reason: spam -- http://master.php.net/manage/user-notes.php?action=delete+48355&report=yes&reason=spam Reason: useless example -- http://master.php.net/manage/user-notes.php?action=delete+48355&report=yes&reason=useless+example Reason: contains commercial links -- http://master.php.net/manage/user-notes.php?action=delete+48355&report=yes&reason=contains+commercial+links Reason: useless note -- http://master.php.net/manage/user-notes.php?action=delete+48355&report=yes&reason=useless+note Reject -- http://master.php.net/manage/user-notes.php?action=reject+48355&report=yes Search -- http://master.php.net/manage/user-notes.php