Resizing images with PHP

* File: SimpleImage.php
* Author: Simon Jarvis
class SimpleImage {

var $image;
var $image_type;

function load($filename) {
$image_info = getimagesize($filename);
$this->image_type = $image_info[2];
if( $this->image_type == IMAGETYPE_JPEG ) {
$this->image = imagecreatefromjpeg($filename);
} elseif( $this->image_type == IMAGETYPE_GIF ) {
$this->image = imagecreatefromgif($filename);
} elseif( $this->image_type == IMAGETYPE_PNG ) {
$this->image = imagecreatefrompng($filename);
}
}

function save($filename, $image_type=IMAGETYPE_JPEG, $compression=75, $permissions=null) {
if( $image_type == IMAGETYPE_JPEG ) {
imagejpeg($this->image,$filename,$compression);
} elseif( $image_type == IMAGETYPE_GIF ) {
imagegif($this->image,$filename);
} elseif( $image_type == IMAGETYPE_PNG ) {
imagepng($this->image,$filename);
}
if( $permissions != null) {
chmod($filename,$permissions);
}
}

function output($image_type=IMAGETYPE_JPEG) {
if( $image_type == IMAGETYPE_JPEG ) {
imagejpeg($this->image);
} elseif( $image_type == IMAGETYPE_GIF ) {
imagegif($this->image);
} elseif( $image_type == IMAGETYPE_PNG ) {
imagepng($this->image);
}
}

function getWidth() {
return imagesx($this->image);
}

function getHeight() {
return imagesy($this->image);
}

function resizeToHeight($height) {
$ratio = $height / $this->getHeight();
$width = $this->getWidth() * $ratio;
$this->resize($width,$height);
}

function resizeToWidth($width) {
$ratio = $width / $this->getWidth();
$height = $this->getheight() * $ratio;
$this->resize($width,$height);
}

function scale($scale) {
$width = $this->getWidth() * $scale/100;
$height = $this->getheight() * $scale/100;
$this->resize($width,$height);
}

function resize($width,$height) {
$new_image = imagecreatetruecolor($width, $height);
imagecopyresampled($new_image, $this->image, 0, 0, 0, 0, $width, $height, $this->getWidth(), $this->getHeight());
$this->image = $new_image;
}
}
?>

-------------------Usage-------------------

Save the above file as SimpleImage.php and take a look at the following examples of how to use the script.

The first example below will load a file named picture.jpg resize it to 250 pixels wide and 400 pixels high and resave it as picture2.jpg

 include('SimpleImage.php');
 $image = new SimpleImage();
 $image->load('picture.jpg');
 $image->resize(250,400);
 $image->save('picture2.jpg');
?>

If you want to resize to a specifed width but keep the dimensions ratio the same then the script can work out the required height for you, just use the resizeToWidth function.

 include('SimpleImage.php');
 $image = new SimpleImage();
 $image->load('picture.jpg');
 $image->resizeToWidth(250);
 $image->save('picture2.jpg');
?>

You may wish to scale an image to a specified percentage like the following which will resize the image to 50% of its original width and height

 include('SimpleImage.php');
 $image = new SimpleImage();
 $image->load('picture.jpg');
 $image->scale(50);
 $image->save('picture2.jpg');
?>

You can of course do more than one thing at once. The following example will create two new images with heights of 200 pixels and 500 pixels

 include('SimpleImage.php');
 $image = new SimpleImage();
 $image->load('picture.jpg');
 $image->resizeToHeight(500);
 $image->save('picture2.jpg');
 $image->resizeToHeight(200);
 $image->save('picture3.jpg');
?>

The output function lets you output the image straight to the browser without having to save the file. Its useful for on the fly thumbnail generation

 header('Content-Type: image/jpeg');
 include('SimpleImage.php');
 $image = new SimpleImage();
 $image->load('picture.jpg');
 $image->resizeToWidth(150);
 $image->output();
?>

More Information:

This script will eventually be developed further to include functions
for easily sharpening, bluring, cropping, brightening and colouring images.