Images

Hello, I try to create a simple image from some data from a database (something like a checkerboard: if $a=1 then red, elseif $a=2 then blue etc). Everthing works fine until the assignment of colors. Whenever I use the whole set of data that I have to display, wrong colors are assigned. Whenever I use small subsets of the whole set, then I have the correct display. I only change the value of the limit from the query and the whole pattern might change drastically. Anybody encountered something similar? Mihai