How to make a charcoal drawing filter

Question

i'm interested in some kind of charcoal-filters like the photoshop Photocopy-Filter or the note-paper. Have someone a paper or some instructions how this filter works?

In best case i want to create the following:

input:

Output:

greetings

Answer 1

I think it's a process akin to pan-sharpening. I could get a quite similar image in gimp by:

• Converting to gray
• Duplicating into two layers
• Lightly blurring one layer
• Edge-detecting in the other layer with a DOG filter with large radius
• Compositing the two layers, playing a bit with the transparency.