Php 4.x Invert And B&w

[markiemrboo]

<?php
$im = imagecreatefromjpeg($_GET['image']);

if ($_GET['invert'] == 1 || $_GET['bw'] == 1) {
 imagetruecolortopalette($im, true, 256);
 $tc = imagecolorstotal($im);
 $maxcol = 255;

 for ($i = 0; $i < $tc; $i++) {
 	$col = imagecolorsforindex($im, $i);

 	if ($_GET['bw'] == 1) {
   $min = min($col['red'],$col['green'],$col['blue']);
   $max = max($col['red'],$col['green'],$col['blue']);
   $bw = ($max + $min) / 2;
   imagecolorset($im, $i, $bw, $bw, $bw);
   $col['red'] = $col['green'] = $col['blue'] = $bw;
 	}

 	if ($_GET['invert'] == 1) {
   // make jpeg compressed black proper black so inverting will make white proper white
   if ($col['red'] <= 10 && $col['green'] <= 10 && $col['blue'] <= 10) {
   	$col['red'] = 0;
   	$col['green'] = 0;
   	$col['blue'] = 0;
   }

   imagecolorset($im, $i, $maxcol - $col['red'], $maxcol - $col['green'], $maxcol - $col['blue']);
 	}
 }
}

header("Content-type: image/jpeg");
imagejpeg($im);
imagedestroy($im);
?>

 

Just a little something I hacked up that I thought I might share. It'll open a jpeg image and invert the colours or make it greyscale (or both). If you've using PHP 5 you can use imagefilter() but, well, I am still using 4.x. Might be useful to someone out there I suppose....