How can the "Dry Brush" Filter from Adobe Photoshop can be implemented in C#?

I am currently creating an application that needs to implement the "Dry Brush" Filter of Adobe Photoshop on a Bitmap.

I have absolutely no idea where to begin.

Here is an example of the original image and what i need the outcome to be: (Since i am a new user i cannot directly post images)

Before:

After:

*Alternatively 开发者_StackOverflow中文版i would like to have the image to look like an oil painting like you can see in the example.

Any help would be appreciated!

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The definition for a dry brush filter is "Dry Brush: It simplifies an image by reducing its range of colors to areas of common color".

Try going through the image, pixel by pixel, and if the pixel is a certain shade of green, just turn it into a general shade of green.