"Most likely, the first time you heard about image filters was
when you had to edit your vacation pictures to remove the 'red eye'
effect or an undesirable face. For such basic purposes, a little
practice and some specialized software such as Adobe Photoshop or
Paint Shop Pro is sufficient to end up with great pictures. But if
you want to go beyond the basics you need to understand what a
picture actually is, what the main algorithms dedicated to image
processing are, and how a programming language, as PHP per example,
can help you. Images are wonderfully malleable, and after you
understand those points, you can develop your own custom image
filters with PHP..."