comparison between shapes

I strongly doubt that there are public domain, general purpose, algorithms that will do what you want. It's simply too complex and too specialized.

That said, however, I would google automated fingerprint and/or face recognition, which presents similar challanges, and someone may have published a paper on their solution.

The challenge you face is to find a way to extract information about features - faces, fingerprints, hand shapes can all be characterized by features - eye separation, mouth width, height from eye mid-line to mouth, etc.

Assuming you're just wanting to process hands, you probably need to extract features such as: location of each fingertip, finger web, width of each finger (segment), perhaps location of mid-point of each knuckle, width of wrist, etc.

If the same hand can be imaged at different apparent sizes, then normalizing on an easy to locate feature - such as distance between index finger tip and first/index finger web - will then give you a pair of identically-scaled images.

As the comments above say, if your image is a vector image, you're half way there. If you have a bitmap, you'll have to apply an edge detection algorithm (which you can find off-the-shelf) first.

Fingertip detection requires detecting the inside and outside of the hand outline, then identifying the pairs of (roughly parallel) lines that are the sides of fingers. These give a finger direction; the tip is then the point on the curved end of the finger that has the greatest extent in the direction of the finger midline.

Have fun. Sounds like you have an interesting project.