Hi there, I'm new to this forum and was hoping someone would be able to answer a question about the unsharp mask filter. I'm doing some image processing for work, and was going through various filters and found that the unsharp mask has some qualities that I like. So I read up on unsharp masking and implemented it in my own program. However, my results aren't quite the same. Put simply: gimp's output has more contrast, and appears somewhat smoother. After playing with my unsharp mask a bit, I downloaded the source to 2.6.11 (possibly a mistake, since I am using the 2.6.10 binary) and found the code that does the unsharp masking (unsharp-mask.c). Now, looking through the code I don't see gimp doing anything really different from me outside of the convolution matrix code. Frankly, I don't understand the convolution matrix code. Why does it take 50 samples and then average them? Is this significant? I tried running some numbers through the equation e^-(x^2/2s^2) in the comments, and ran that through a calculator. The numbers largely came out negative, but when I used those numbers they gave obviously incorrect output (hugely overexposed appearance). Are there any other non-standard tweaks to this algorithm that I haven't spotted yet? I'm currently using a simple convolution of: .1, .2, .4, .2, .1 For a similar sized convolution matrix, what would gimp be using? My development environment isn't set up to compile gimp. Thanks for any assistance! -- bioster (via gimpusers.com) _______________________________________________ Gimp-developer mailing list Gimp-developer@xxxxxxxxxxxxxxxxxxxxxx https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer
