How do I convert a set of polygons into a bitmap

How do I take a set of polygons which contain arbitrary values and create a corresponding bitmap where each pixel contains the value of the polygon at that location?

To put the question into context, my polygons contain information about the average number of people per square kilometre within the polygon. I need to create a raster/bitmap that contains pixels representing the population in 200 metre bins.

I've done something similar in the past where I've used a polygon to create a mask by drawing into a bitmap and filling values, then converting the bitmap into an array that I can manipulate. I'm sure there's a better method for doing this!

I'm clarifying the question a bit more as requested.

There are multiple polygons, each polygon is a set of vectors
Each polygon will have a single unique value
The polygons don't overlap

Thanks

Nick

Solution

@Nick R

I was originally using ArcGIS 9.2, but that doesn't work well with C# and 64 bit, so I am now using GDAL (http://www.gdal.org).

Doesn't gdal_rasterize do exactly what you want?