filterDibGray3x3

Definition: filterDibGray3x3(a32Dib dib, sequence matrix, integer div, integer bias)
Description: Applies a matrix-filter to the bitmap:
matrix is a 3x3 sequence with the multiplication-values
div is the number to divide the result by
bias is the number to add to the result
Comments: new_pixel[y][x] = sum_of(matrix[i][j] * old_pixel[y-4+i][x-4+j]) / div + bias