filters and generator should accept and produce sequences of images. Each sequence has the following format:

width           unsigned 4 bytes big-endian
height          unsigned 4 bytes big-endian

followed by one or more arrays of pixels:

pixels          array of 4 byte big-endian ARGB pixels, width * height in length
                    pixel_index(x, y) = x + y * width

if a filter does not use alpha in any way it's best practice to copy the input alpha to the output.