peterson%ring@UTAH-CS.ARPA.UUCP (01/20/87)
If the DN5/660 you're using has all of the available color memory (i.e., both cards) you should be able to use gpr_$read/write_pixels for eight bit images in "direct" mode. The key is to avoid doing any operations a pixel at a time - doing so essentially wastes the display hardware for doing this. For your application it sounds like you might be better off storing and processing the image in off screen memory, and updating the screen by calling gpr_$write_pixels once for the entire image. This happens very quickly. As for displaying 24 bit images, it's probably not worth the hassle to use this "feature" of the Apollo color hardware if you want anything that's even remotly interactive. Apollo's newer workstations (570, 580, 3000, etc) don't even support 24 bit color in any mode (boo hiss...). For working with full color images, you can try dithering or quantizing the image from 24 bits to eight. We've written some dithering software for the Utah Raster Toolkit that works quite well. Somebody at apollo wrote a color quantizer based on Paul Heckbert's SIGGRAPH 82 paper - they use it for displaying their flashy ray-tracing pictures. It produces very nice results but doesn't run very fast... Cheers, John Peterson (peterson@cs.utah.edu) -------