This picture is made up with all prime numbers from 2 up to 480,000

The prime numbers start at bottom left hand corner and work up to the top right hand corner as you can see their is a pattern where their are no prime numbers, the vertical are the numbers 1,3,7,9 the diagonal are the numbers at their maximum magnitude before going Prime² you are welcome to copy this file as long as you keep it, as it is with copyright.

If you load the picture in to paint and flip the picture over vertical you can easily see where each prime pairs are and if you use the x,y pointer you can workout the prime number, point to any white square you can calculate the prime number with this formula.

 X+1+Y*800 so X=100,Y=24  would equal 100+1 + (24 * 800) equal prime 19301 try it.

It would be easy to write a program to interface with this picture to test for prime, you would just need to add an offset for the header then test each byte 0 = not prime and 255 = prime... to easy... std bitmap 800x600 = 480,000 bits

Easy test, count the bits from bottom left and every white bit is equal to prime.

This is what the bottom left corner of the prime map looks like.

It's black and white.