Convolutiuon of an image using DSP builder

When you are doing your filter, you are adding the pixel values but they are in uint8 format, so the sum can't get above 255. You have to make sure that the bit widths accommodate your sum to get large enough. ALSO you need to divide the result by your filter size. So if you are doing a 3x3 blur you should be adding the pixel values of the 9 pixels and then dividing the sum by 9.

In the attached simulink file, i simply did 3x3 blurring (as an average of pixel values) on the individual R,G,B channels. The blurring works if all your bitwidths are set correctly. For example the accumulator bitwidth is set to 16 instead of 8 (although 16 is far too much). Then I also have a gain block of 1/9 to average the sums. Also I'm just using the native simulink library, not dsp builder but the concepts remain.