[konidias]

There are multiple ways to do it. You could have the food value have a max of 100 and a min of 1. Then you just do something like:

changeimgpart index,0,0,foodvalue,10;

Which would make the food bar display from an x of 0 to an x of whatever your food value is... like if it were 50, it would display from 0 to 50, which would be half the bar, if your bar was 100 pixels in width.

Otherwise you're going to need a small formula to adjust for the difference in pixel width to food value.