Where can I find an unsharp mask for C#?

Question

I have been trying to find a code snippet to do an unsharp mask in C# but cant find one that works or is complete. I found a PHP version but I would like to find one in C# before I go through all the hard work converting this from PHP.

I am just a beginner. Can anyone point me in the right direction?

Answer 1

See if this blog entry helps you in the right direction:

http://anand-vinay.blogspot.com/2008/01/unsharp-mask-in-cnet.html

Edit: Okay that blog entry did not work, sorry for the bad link.

I did find a complete application that you can download with source which has the code that I think you are looking for.

http://www.ctyeung.com/Csharp/index.html

Answer 2

The AForge.NET Framework includes many image processing filters and support plugging your own. You can see it in action in their own Image Processing Lab application.

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UPDATE: AForge.NET has a convolution-based sharpen filter (see convolution filters), but there's no mention of an unsharp mask filter per se. Then again, you can use the Gaussian blur filter and subtract the result from the original image, which is basically what the unsharp mask filter does. Or maybe the basic sharpen is enough for your needs.

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UPDATE: Looked further, and AForge.NET does have a Gaussian sharpen which seems to be an implemenation of an unsharp mask filter, and you can control some parameters.

Answer 3

Christian Graus's Image Processing for Dummies with C# part 2 contains source code, and an explanation of how you can do unsharpen (assuming you mean smoothing). The whole series is an excellent introduction to image processing with GDI (in C#) and requires no external libraries.

Answer 4

Would you care to use FFTs? Transform, remove or accentuate high freqs to taste, invert the transform, recombine with the original if desired? Hardly any licensing issues there, as FFT libraries abound.

Alternately, you can make up masks by hand, varying size and constants as you like, then convolve them with your image pixels (nested 'for' loops ...).

Here's a 3x3x1 mask as a text file with its dimensions given before the values:

//3x3x1

// x size

3

// y size

3

//z size

1

//z = 0

2 3 2

3 5 3

2 3 2

//end

This can be extended to 3 dimensions (hence the z size being given).

Answer 5

The latest version of the open source C# Image Library has an unsharp mask filter (as well as gaussian blur, brightness/contrast etc) and is very easy to use.

You'll find a tutorial how to apply an unsharp mask here.