online t-shirt printing - removing white from image upload

Question

Some Background Info: Basically I am looking to re-create a image upload onto a tshirt facility. This has been successful until the point where I need to remove the colour white from uploaded images to remove background colour. Flash is not an option im afraid, the upload facility script is written in PHP along with the use of jQuery drag to move and resize the images and test on the shirt.

A good example would be found at http://www.zazzle.co.uk where an option to "show whites in image as transparent" is available if you click on advanced options. I would like to imitate this feature however I am having problems figuring it out.

Any help would be great, just a point in the right direction? I have looked at using Jquery, PHP, ImageMagick but to no avail...

Answer 1

ImageMagick can do it. Not sure why you've had no luck with that.

example ImageMagick command:

convert input.gif -transparent white output.gif

However, this will only work for pure white on the image. Not if it's slightly off white.