This class eases handling image uploads a lot.
Firstly, it checks if the file is a valid image, that is no larger than a 
maximum you can set in the constants. Then it checks if the image file is 
actually valid, by loading it into an image resource.

Then, you can resize said image. The image that will contain the resized version
gets its own ID. Resizing can be done in 3 ways: absolute stretch, shrink but 
keep aspect ratio, or crop center to resize to absolute dimensions.
Then, files can be saved in either JPG, GIF or PNG. For JPG, you can specify a 
quality of 1-100.

When working with many different versions of the image, the class stores the 
image that's not being worked with away as a full-quality PNG, in a temporary 
folder. These temporary files are deleted when the instance is unset or the
script terminates, so it doesn't leave any waste behind.

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Basic Usage:

1) Include the class in your script.
2) Instantiate an image handler:

    $ih = new ImageHandler($cur_file, ImageHandler::TYPE_ALL);

  where $cur_file is a valid file from the $_FILES superglobal
3) (optional, but recommended) Check whether the handler initialized correctly.

    if($ih->IsInitialized()) { ... }

4) Create a resized version of the uploaded image

    $ih->Resize('id_for_resized_img', ImageHandler::RESIZE_SHRINK_KEEP_ASPECT,
      400, 300); //For a width of 400px, height of 300px.

5) Save to a new image file

    $ih->Save('id_for_resized_img', 'path/to/folder/', 'base_filename',
      ImageHandler::TYPE_JPEG);

6) Done!

Note: most of these functions (like Resize and Save) return a boolean informing
you of the success of the requested operation.
Any error information is available in public properties $ih->SafeErrorMessage 
and $ih->DebugErrorMessage.