Constant (large) 2D array of unsigned declaration

[nabla101]

Hi, I want to declare four constant arrays to emulate four frames of a VGA resolution video sequence, to use for simulation of a video CODEC. I am only considering luminance values to begin with, which have values from 0 (black) to 255 (white). I want to use a simple pattern like a cross moving across a background of a different shade for the emulated video sequence. I want to know if anyone has any ideas on how I can easily define the arrays using a formula, or from a file for example since there are 19200 unsigned elements in each 2D array, too many to define practically.

I was thinking of starting like this:

type PXL is unsigned 0 to 255;
type VGA_frame is array (0 to 639, 0 to 479) of PXL;

constant frame_0 : VGA_frame := ( ..... 
                                                ..... )

But obviously that would take impossibly long to do, so is there another way?

 

[TrickyDicky]

If you are using modelsim, you can read/write binary files directly, which allows you to read bitmap files. Unfortunatly, with other simulators its not so simple or impossible.

Otherwise you can store all the data in a text file, or PGM (portable grey map) which is an ascii formatted image file - see here:
PGM Format Specification

If you do all this right, you can declare the VGA frame as:

type PXL is natural 0 to 255; --unsigned type is not appropriate here
type VGA_frame is array(natural range <>, natural range<>) of PXL;

and then read from the file to set the dimentsion on an array, but Ill leave those details up to you.