<?php
 
function paGdThumbnail($image, $max_width, $max_height, $method = 'scale', $bgColour = null)
{
	// get the current dimensions of the image
	$src_width = imagesx($image);
	$src_height = imagesy($image);
 
	// if either max_width or max_height are 0 or null then calculate it proportionally
	if( !$max_width ){
		$max_width = $src_width / ($src_height / $max_height);
	}
	elseif( !$max_height ){
		$max_height = $src_height / ($src_width / $max_width);
	}
 
	// initialize some variables
	$thumb_x = $thumb_y = 0;	// offset into thumbination image
 
	// if scaling the image calculate the dest width and height
	$dx = $src_width / $max_width;
	$dy = $src_height / $max_height;
	if( $method == 'scale' ){
		$d = max($dx,$dy);
	}
	// otherwise assume cropping image
	else{
		$d = min($dx, $dy);
	}
	$new_width = $src_width / $d;
	$new_height = $src_height / $d;
	// sanity check to make sure neither is zero
	$new_width = max(1,$new_width);
	$new_height = max(1,$new_height);
 
	$thumb_width = min($max_width, $new_width);
	$thumb_height = min($max_height, $new_height);
 
	// if bgColour is an array of rgb values, then we will always create a thumbnail image of exactly
	// max_width x max_height
	if( is_array($bgColour) ){
		$thumb_width = $max_width;
		$thumb_height = $max_height;
		$thumb_x = ($thumb_width - $new_width) / 2;
		$thumb_y = ($thumb_height - $new_height) / 2;
	}
	else{
		$thumb_x = ($thumb_width - $new_width) / 2;
		$thumb_y = ($thumb_height - $new_height) / 2;
	}
 
	// create a new image to hold the thumbnail
	$thumb = imagecreatetruecolor($thumb_width, $thumb_height);
	if( is_array($bgColour) ){
		$bg = imagecolorallocate($thumb, $bgColour[0], $bgColour[1], $bgColour[2]);
		imagefill($thumb,0,0,$bg);
	}
 
	// copy from the source to the thumbnail
	imagecopyresampled($thumb, $image, $thumb_x, $thumb_y, 0, 0, $new_width, $new_height, $src_width, $src_height);
	return $thumb;
}