resimagecrop.php

<?php
// resimagecrop - version 0.0.2
// RESS based solution for cropping images for responsive design
// Most definitely a work in progress!

// Author - Ian Devlin
// Twitter - @iandevlin
// Web - iandevlin.com

// $image - the original image
// $x - the x position to begin the crop from (percentage)
// $y - the y position to begin the crop from (percentage)
// $w - the width of the amount to crop (pixels)
// $h - the height of the amount to crop (pixels)
// $sc - the scale factor (decimal)
//
// For example
// resimagecrop.php?image=img/image-to-use.jpg&x=15&y=20&w=550&h=450&sc=0.5
// begins the crop of img/image-to-use.jpg at 15% from the top and 20% from the left and will crop a width of 550x450 and then scale it by 0.5 (resulting image is 275x225)
//

// Collect parameters
$img = getParam('image');
$x = intval(getParam('x'));
$y = intval(getParam('y'));
$w = intval(getParam('w'));
$h = intval(getParam('h'));
$sc = getParam('sc');
if ($img) {
	// Do a little prep to find the filename of the resized and scaled file, so we can test if it's cached
	$w ? $width = '-' . $w : $width = '';
	$h ? $height = 'x' . $h : $height = '';
	$x ? $xcrop = '-' . $x : $xcrop = '';
	$y ? $ycrop = 'x' . $y : $ycrop = '';
	$sc ? $scale = '-' . $sc : $scale = '';
	$pi = pathinfo($img);

	// Define the cachefile
	$cachefile = 'temp/' . basename($img, '.' . $pi['extension']) . $width . $height . $xcrop . $ycrop . $scale . '.' . $pi['extension'];

	if (!file_exists($cachefile)) {
		// Get a handle to the original image
		$i = imagecreatefromjpeg($img);        
		// Get the dimensions of the original image
		$size = getimagesize($img);
		$origWidth = intval($size[0]);
		$origHeight = intval($size[1]);
		// If x, y, w, and h parameters have been passed...
		if ($x && $y && $w && $h) {
			// Work out the x and y co-ordinates of the original image where the crop is to begin
			$cx = ($origWidth * $x) / 100;
			$cy = ($origHeight * $y) / 100;
			// Create a new image with the required width and height
			$ci = imagecreatetruecolor($w, $h);
			// Crop the image
			imagecopy($ci, $i, 0, 0, $cx, $cy, $origWidth, $origHeight);
			$i = $ci;
		}
		// If scaling is required...
		if ($sc) {
			if (!$w) $w = $origWidth;
			if (!$h) $h = $origHeight;
			// Define the width and height of the new scaled image
			$scw = $w * $sc;
			$sch = $h * $sc;
			// Scale the image
			$sci = imagecreatetruecolor($scw, $sch);
			imagecopyresampled($sci, isset($ci) ? $ci : $i, 0, 0, 0, 0, $scw, $sch, $w, $h);
			$i = $sci;
		}
		// Create cache file
		imagejpeg($i, $cachefile);
	}
	// Return file
	header('Content-Type: image/jpg');
	header('Content-Disposition: attachment; filename=' . $img);
	readfile($cachefile);
	// Tidy up
	imagedestroy($i);
}

// Extracts parameters
function getParam($name) {
	if (isset($_GET[$name])) return htmlspecialchars($_GET[$name]);
	return '';
}