What are the algorithms used behind filters in image editing softwares?

Question

For example: What algorithm is used to generate the image by the fresco filter in Adobe Photoshop?

Do you know some place where I can read about the algorithms implemented in these filters?

Answer 1

Lode's Computer Graphics Tutorial

Answer 2

The source code for GIMP would be a good place to start. If the code for some filter doesn't make sense, at least you'll find jargon in the code and comments that can be googled.

Answer 3

The Photoshop algorithms can get very complex, and beyond simple blurring and sharpening, each one is a topic unto itself.

For the fresco filter, you might want to start with an SO question on how to cartoon-ify and image.

I'd love to read a collection of the more interesting algorithms, but I don't know of such a compilation.

Answer 4

Digital image processing is the use of computer algorithms to perform image processing on digital images. As a subcategory or field of digital signal processing, digital image processing has many advantages over analog image processing. It allows a much wider range of algorithms to be applied to the input data and can avoid problems such as the build-up of noise and signal distortion during processing. Since images are defined over two dimensions (perhaps more) digital image processing may be modeled in the form of multidimensional systems.
Digital image processing allows the use of much more complex algorithms, and hence, can offer both more sophisticated performance at simple tasks, and the implementation of methods which would be impossible by analog means.
In particular, digital image processing is the only practical technology for:
Classification
Feature extraction
Pattern recognition
Projection
Multi-scale signal analysis

Some techniques which are used in digital image processing include:

Pixelation, Linear filtering, Principal components analysis
Independent component analysis
Hidden Markov models
Anisotropic diffusion
Partial differential equations
Self-organizing maps
Neural networks
Wavelets