c# - Creating rectangles from the inner part of a texture2D

This may be hard to understand, but I'll do my best.

You will see that the first image is a normal Mario, and the other is the result I am looking for. I'm trying to find a way to extract rectangles (biggest possible to smallest) from a texture2D, without overlapping rectangles. If the pixel is completely transparent, leave it out of the loop. I know it would be really easy to implement a rectangle for every pixel, but millions of rectangles isn't going to help performance wise. The goal is to get rectangles somewhat like this, decreasing the total rectangles greatly.

Any ideas or links? Anything would be great.