Reading only parts of images, tiles

Hi,

Is there any class which is able to read only a specific part of a given image? I can read and display entire images with "Forms" just fine, but it does not seem to permit me reading only parts of it. 
The reason i'm asking this is because i want to implement a simple tile graphics engine, so i need a way to break down images into single parts.

Thanks in advance,
Peter Schneider
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