I have the original image and filtered image.
These images are from pixiv WHICH IS NOT AT ALL SAFE FOR WORK: http://www.pixiv.net/member_illust.php?mode=manga&illust_id=43697578
It look like a linear FIR filter which mean blurred image = original image perform convolution with some window function
In theory from this 2 images I can find the window function but I don't know how to do that in practice. Do I need some tools or software to analyze?
The main question is what kind of blur filter is this? (Or if it doesn't has particular name I'm asking about window function. a name, a plot, anything)
And if you can tell by using some method or tools (not just your experience or instinct) could you tell me how?