general matrix multiplication/manipulation, convolution modification

[cityhunter]

hello,
i'm greatly intersted in image manipulation using opengl image subset but :
* i've not found a general way to multiply image matrix with a special fx matrix, this could be used to FFT or some other transform
* i wanted to use convolution to build tools as blur but opengl matrix convolution does not allow to do
C[i',j']=sum(n=-wf/2,wf/2)sum(m=-hf/2,hf/2)CS[i+n,j+m]cf[n+wf/2,m+wh/2]
i want to acces value that are lower indexed that the value i want to modify
*there is no way to use matrix algebra which can be used for most of image manipulation...

[cityhunter]

is there someone interested or is my question too hard?