2008/7/24 Elliott Slaughter <[EMAIL PROTECTED]>: > I've been working on my game again lately, and one thing I would like to do > is collision detection. To make collision detection sufficiently accurate, I > figure I'll need some sort of pixel perfect algorithm, for which I need > access to the pixels of a surface. Thanks to a previous discussion on this > mailing list, I already know how to do that, but what I *don't* know is how > to find the color key of a surface so I can figure out if a pixel is > transparent or not. There are functions for set-color-key and > clear-color-key but I don't see any get-color-key, and I'm not really sure > how to get it, except by saving the argument passed to load-image and > constructing the color-key manually. > > Also, I think I know a reasonably decent algorithm for collision detection, > but any suggestions on the topic would be appreciated anyways ;-) > > Thanks! > > P.S. I've been wondering why the keyword arguments to load-image are > :key-color and :key-color-at instead of :color-key and :color-key-at (not > that it really matters, it's just a fascinating anomaly).
SDL doesn't have an API for retrieving the color key. You've got three options: 1) Remember the color key when you load the image. 2) Access the colorkey value using cffi. Given a surface pointer, there is a field format (a SDL_PixelFormat) and inside that is the colorkey in a field called colorkey. (Uint32). 3) Write, or wait for someone to write, lisp code that does 2) and submit to lispbuilder. Justin _______________________________________________ application-builder mailing list application-builder@lispniks.com http://www.lispniks.com/mailman/listinfo/application-builder
