What is ImageMagick?

ImageMagick is a powerful set of image manipulation utilities. It can read, write and manipulate images in many image formats. It can resize, rotate, sharpen, color reduce or add any other special effect to your images. And, best of all, ImageMagick is directly available from the command line. In this article, we will write a script to make it available from the query string. You can then use it, for example, to automatically generate thumbnails of your images.

What our script will do

We will write a script that we can copy-paste in a directory with images and that enables us to use ImageMagick's convert utility on each of the images in that directory. The script will enable us to give convert commands by changing the query string.
Maybe a simple example will better explain this idea. You've got an image: http://wwww.example.com/img/image.jpg. You copy the ImageMagick script magick.phpto the same directory. The image is now also available as http://www.example.com/img/magick.php/image.jpg. So far, your image hasn't changed. Now, imagine you want a thumbnail of the image with a width of exactly 200 pixels. You can get that image by requesting the url: http://www.example.com/img/magick.php/image.jpg?resize(200).

On receiving a request, the script will:

1. Parse the query string
2. Convert the query string to an ImageMagick command string
3. Run ImageMagick on the image
4. Send the modified image to the browser.

As you see, the script will run ImageMagick for every request. This isn't very efficient. As you will probably use just a few commands (e.g. thumbnail and original image) in your html files, caching the output will speed up the system. We will add a point 5 to the list. The output of ImageMagick should be cached. The script should send the cached image if it exists, so ImageMagick won't be generating the same image over and over again.