[whatwg] Image Collision Detection in Canvas

Saurabh Jain saurabh at skjworld.com
Sun Apr 4 04:50:39 PDT 2010


I have a proposal for adding generic image collision API in Canvas. Given
two images HTMLImageElement objects and there respective x, y, clip width
and clip height the API call will let you know if there's any
non-transparent pixel (any opaque or translucent pixel) in one image's
clipping region that overlaps a non-transparent pixel in another image's
clipping region. The clipping region defined by this API call is for local
use only for this purpose.

This API will be useful for game programmers. I am author of India's first
book on J2ME and have been developing mobile games since 2002. I have
through personal experience observed that this pixel level collision at
native level is required for game developers to build games easily. What I
am referring to is a kind of generic pixel level collision. People are free
to develop there own complex collision mechanisms for complex games but
small teams composed of new game developers find image collision detection
implementation the most difficult concept in the whole game development
process to grasp.

Also pixel level checking for two 100 pixel x 100pixel images will involve
lot of execution time if done at JavaScript level since up to 10000 checks
may have to be performed. Native browser support can speed things a lot.
Similar thing happened in J2ME where before MIDP 2.0 people had hard time to
do pixel level collision both due to programming complexity and execution

Saurabh Jain
SKJ Technologies Private Limited
Author : Mobile Phone Programming using Java ME (J2ME)
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