"frame: Full image specified as a Active pixels per line-by-Active video lines-by-N matrix. Height and width are the dimensions of the active image specified in Video format. N is the Number of components used to express a single pixel."
That could be an arbitrary data matrix from some source, including from a file you have read in.
You can use Custom to give an arbitrary size equal to your image size. Active pixels per line is your image with. Active lines is your image height. For the front porch and back porch, calculate according to the guidelines given there:
"Also, set the horizontal blanking interval, or Back porch + Front porch, according to these guidelines.
- The total of Back porch + Front porch must be at least 2 times the largest kernel size of the algorithm in the blocks following the Frame To Pixel block. If the kernel size is < 4, the total porch must be at least 8 pixels.
- The Back porch must be at least 6 pixels. This parameter is the number of inactive pixels before the first valid pixel in a frame."
This does not require that you modify the image at all.