lowpass filtering in vhdl
A simple weighted average of pixels surrounding the target pixel will do that. Clearly you have to do it in 2D. Step and repeat for each pixel. There are a lot of calculations so try and limit yourself to maybe a 3x3 array or a 5x5 to begin with. Make sure you update pixels to a new target picture and don't overwrite the original (until you have finished).



This is a FIR type algorithm. And the one below is a gaussian smoothing 5 x 5 filter: -



Picture source

Notice the symmetry of the weighting factors with the most weight being given to the middle pixel.