Tutorial Server Side Image Resizer

by in , 0

The code uses PHP to resize an image (currently only jpeg). Using this method, the resized image is of much better quality than a browser-side resizing. The file size of the new downsized image is also smaller (quicker to download).

The code comes in two parts:

imageResizer() is used to process the image loadimage() inserts the image url in a simpler format 
<?php

   function imageResizer($url, $width, $height) {

		header('Content-type: image/jpeg');

		list($width_orig, $height_orig) = getimagesize($url);

		$ratio_orig = $width_orig/$height_orig;

		if ($width/$height > $ratio_orig) {
		  $width = $height*$ratio_orig;
		} else {
		  $height = $width/$ratio_orig;
		}

		// This resamples the image
		$image_p = imagecreatetruecolor($width, $height);
		$image = imagecreatefromjpeg($url);
		imagecopyresampled($image_p, $image, 0, 0, 0, 0, $width, $height, $width_orig, $height_orig);

		// Output the image
		imagejpeg($image_p, null, 100);
		
	}

	//works with both POST and GET
	$method = $_SERVER['REQUEST_METHOD'];
	
	if ($method == 'GET') {

		imageResize($_GET['url'], $_GET['w'], $_GET['h']);
		
	 } elseif ($method == 'POST') {

	    imageResize($_POST['url'], $_POST['w'], $_POST['h']);
	 }

	// makes the process simpler
	function loadImage($url, $width, $height){
         echo 'image.php?url=', urlencode($url) ,
         '&w=',$width,
         '&h=',$height;
	}

?>

Usage

Above code would be in a file called image.php.

Images would be displayed like this:

<img src="<?php loadImage('image.jpg', 50, 50) ?>"

Leave a Reply