Love Mike G

ImageModifier: A PHP Thumbnail Generator

If you have ever written a web application that allows users to upload images, you have encountered the need for automated thumbnail generation. Here’s my version.

I’ve placed a few static methods at the top to simplify the process a bit. The whole script is commented pretty heavily so you should be able to figure it out.

On-the-Fly Resizing

To load an image in, constrain it to a 500×500 bounding box, and render it directly to the browser:

<?php
require('lib/ImageModifier.php');
ImageModifier::ResizeAndRender('path/to/source.jpg', 500);
?>

You can even offer the file for download just by adding ‘true’ at the end of the method call:

<?php
require('lib/ImageModifier.php');
ImageModifier::ResizeAndRender('path/to/source.jpg', 500,true);
?>

Saving Resized Files on the Server

On-the-fly resizing isn’t exactly the most optimal solution for a public views. Each request will require the image to be loaded, resampled, and passed. Any more than one or two concurrent connections could bring your server down to a crawl. Instead, you can cache the images by saving the outputted image to a folder on the server. Just make sure that you give Apache write permission to the destination directory.

<?php
require('lib/ImageModifier.php');
ImageModifier::ResizeAndSave('path/to/source.jpg', 500, 'path/to/resized/destination.jpg');
?>

Download & Code

You can download the code or check it out below.

<?php

class ImageModifier {
    
    private $filename;
    private $width;
    private $height;
    private $type;
    private $type_whitelist = array(1,2,3);
    private $image;
    
    # 
    # ResizeAndSave
    # -------------------------------------------------------------------------
    # Loads, resizes, and saves an image as a single batch operation.
    #
    # Parameters
    #   - string source: The source image to load.
    #   - int|float bounds: The bounds to resize within. If a fractional number
    #       less than one is passed, it is interpreted as the percentage to 
    #       resize to. Otherwise, it is interpreted as the bounding box size.
    #   - string destination: The destination path and filename to save to.
    # 
    
    public static function ResizeAndSave($source, $bounds, $destination) {
        $temp = new ImageModifier;
        
        $temp->load($source);
        $temp->resize($bounds);
        $temp->save($destination);
        
        unset($temp);
    }
    
    # 
    # ResizeAndRender
    # -------------------------------------------------------------------------
    # Loads, resizes, and saves an image as a single batch operation.
    #
    # Parameters
    #   - string source: The source image to load.
    #   - int|float bounds: The bounds to resize within. If a fractional number
    #       less than one is passed, it is interpreted as the percentage to 
    #       resize to. Otherwise, it is interpreted as the bounding box size.
    #   - bool download: Optional. Offers the image for download instead of
    #       a direct render.
    #
    
    public static function ResizeAndRender($source, $bounds, $download=false) {
        $temp = new ImageModifier;
        
        $temp->load($source);
        $temp->resize($bounds);
        $temp->render($download);
        
        unset($temp);
    }
    
    # 
    # load
    # -------------------------------------------------------------------------
    # Loads an external image from the filestystem, sets class properties, and
    # creates an image resource.
    #
    # Parameters
    #   - string file: The path and filename of the source image.
    # 
    
    public function load($file) {
        if(file_exists($file) && is_readable($file)) {
            $imagesize = @getimagesize($file);
            
            if(!empty($imagesize)) {
                if(isset($imagesize[2]) && in_array($imagesize[2], $this->type_whitelist)) {
                    $this->filename = $file;
                    $this->width = $imagesize[0];
                    $this->height = $imagesize[1];
                    $this->type = $imagesize[2];
                    
                    $this->imageCreate();
                }
            }
        }
    }
    
    # 
    # imageCreate
    # -------------------------------------------------------------------------
    # Creates the image resource used to store the source image for resizing.
    #
    # Parameters
    #   - none
    # 
    
    private function imageCreate() {
        switch($this->type) {
            case 1: 
                $this->image = imageCreateFromGIF($this->filename);
                break;
            case 2: 
                $this->image = imageCreateFromJPEG($this->filename);
                break;
            case 3:
                $this->image = imageCreateFromPNG($this->filename);
                break;
        }
    }
    
    # 
    # resize
    # -------------------------------------------------------------------------
    # Resizes and resamples the image.
    #
    # Parameters
    #   - int|float bounds: The bounds to resize within. If a fractional number
    #       less than one is passed, it is interpreted as the percentage to 
    #       resize to. Otherwise, it is interpreted as the bounding box size.
    # 
    
    public function resize($bounds) {
        if($bounds < 1) {
            $percent =& $bounds;
        }
        else {
            $percent = ($this->width > $this->height) 
                ? $bounds / $this->width 
                : $bounds / $this->height;
        }
        
        $newWidth = $this->width * $percent;
        $newHeight = $this->height * $percent;
        
        $newImage = imageCreateTrueColor($newWidth, $newHeight);
        
        imageCopyResampled(
                $newImage, 
                $this->image, 
                0, 0, 0, 0, 
                $newWidth, 
                $newHeight, 
                $this->width, 
                $this->height
            );
        
        $this->image = $newImage;
    }
    
    # 
    # render
    # -------------------------------------------------------------------------
    # Passes the image to the browser.
    #
    # Parameters
    #   - bool download: Optional. Offers the image for download instead of
    #       a direct render.
    #   
    
    public function render($download=false) {
        header('Content-type: '.image_type_to_mime_type($this->type));
        
        if($download) {
            header('Content-Disposition: attachment; filename="'.basename($this->filename).'"');
        }
        
        switch($this->type) {
            case 1: 
                imageGIF($this->image);
                break;
            case 2: 
                imageJPEG($this->image);
                break;
            case 3:
                imagePNG($this->image);
                break;
        }
    }
    
    # 
    # save
    # -------------------------------------------------------------------------
    # Saves the resized image to the filesystem.
    #
    # Parameters
    #   - string filename: The path and filename of the saved image.
    # 
    
    public function save($filename) {
        switch($this->type) {
            case 1: 
                @imageGIF($this->image, $filename);
                break;
            case 2: 
                @imageJPEG($this->image, $filename);
                break;
            case 3:
                @imagePNG($this->image, $filename);
                break;
        }
    }
    
}

?>

This entry was posted on Monday, March 19th, 2007 at 11:39 am and is filed under PHP. Both comments and pings are currently closed.

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