I'm trying to port the picturing-programs teachpack to still work with 5.1. (BTW, approximately how long do I have to do that before 5.1 is released?) Right now it crashes because the API for make-bitmap has changed -- for the better, I think, but I still need to fix things.
I've got a "map-image" function that creates a [bitmap] image the same width and height as an existing image by mapping a color->color function on its pixels, and a "build-image" function that creates a [bitmap] image of a specified width and height by mapping a specified function on the coordinates of its pixels. I also wrote (but didn't really document) a "map-masked-image" and "build-masked-image" which do the same, but the mapped function is also allowed to return #f, in which case the specified pixel is made transparent (i.e. alpha=0). I can tweak those to work with the new make-bitmap, but the process got me wondering... It would be nice if I could allow students to generate alphas other than 1 and 0. It seems to me the cleanest way to do this is with an alpha-color struct (which existed in htdp/image, but seems to be gone from 2htdp/image). I can do that myself, putting in glue code between it and 2htdp/image to convert back and forth among various color-like-things (color, alpha-color, string, symbol, color%, and #f for transparency), but 2htdp/image is already doing a lot of that, and it feels really inefficient to re-do it. What would you think of ALL "color" structs actually having an alpha component, with the constructor allowing alpha to default to 1? Stephen Bloch sbl...@adelphi.edu _________________________________________________ For list-related administrative tasks: http://lists.racket-lang.org/listinfo/users
