Trim a Solid color border from an image using GDlib in PHP

imagetim.php

<?php

function imagetrim(&$im) {
	
	$width = imagesx($im);
	$height = imagesy($im);
	
	$imcopy = imagecreatetruecolor($width, $height);
	imagecopy($imcopy, $im, 0, 0, 0, 0, $width, $height);
	imagefilter($imcopy, IMG_FILTER_GAUSSIAN_BLUR);
	imagetruecolortopalette($imcopy, false, 32);
	
	$bg = imagecolorat($imcopy, 0, 0);
	
	$xmin = $width;
	$ymin = $height;
	
	$xmax = 0;
	$ymax = 0;
	
	foreach (range($height - 1, 0) as $y) {
		foreach (range($width - 1, 0) as $x) {
			if (imagecolorat($imcopy, $x, $y) != $bg) {
				if ($x > $xmax) {
					$xmax = $x;
				}
				if ($y > $ymax) {
					$ymax = $y;
				}
				if ($x < $xmin) {
					$xmin = $x;
				}
				if ($y < $ymin) {
					$ymin = $y;
				}
			}
		}
	}
	
	$newwidth = $xmax - $xmin;
	$newheight = $ymax - $ymin;
	
	$im2 = imagecreatetruecolor($newwidth, $newheight);
	$bg2 = 
	imagecolorallocate($im2, 255, 255, 255); // white
	imagefill($im2, 0, 0, $bg2);
	imagecopy($im2, $im, 0, 0, $xmin, $ymin, $newwidth, $newheight);
	
	$im = $im2;
	imagedestroy($imcopy);
}