kuyp@wyn386.mi.org@wybbs.mi.org (kuyp@wyn386.mi.org) (06/25/91)
Help! I am looking for a method to convert 32 Bit color Sunraster files to Black & White Images. These Images have to look good!? I can and have converted them to 4 eight bit images and picked the best looking B&W, but would like a more exact way, you do not always get a good looking image from just one color. Anybody have any ideas? Please let me know! Mail me direct, I do not always get these news feeds. Gary Kuyper kuyp@wybbs.mi.org thanks all!!
falk@peregrine.Sun.COM (Ed Falk) (07/01/91)
In article <620@wybbs.mi.org> kuyp@wyn386.mi.org@wybbs.mi.org (kuyp@wyn386.mi.org) writes: > >I am looking for a method to convert 32 Bit color Sunraster files to >Black & White Images. These Images have to look good!? > >I can and have converted them to 4 eight bit images and picked the >best looking B&W, but would like a more exact way, you do not always >get a good looking image from just one color. I'm confused, are you trying to get 8-bit greyscale out or 1-bit monochrome? In the former case, the FAQ list mentions that the customary function is .299r + .587g + .144b These numbers were invented the the NTSC (national television standards committee?), but you can get reasonable results with just r/3 + g/3 + b/3 if you're lazy. In a 32-bit sunraster file, the high-order byte is alpha, and can be ignored. The low order three bytes are either rgb (blue lowest) for format RT_FORMAT_RGB or bgr (red lowest) for RT_STANDARD. To convert to a 1-bit monochrome picture, first convert to greyscale and use one of the "dithering" techniques described in Foley & VanDam. Software to do all this can be found in the pbm and fbm packages. See the FAQ list. -ed falk, sun microsystems sun!falk, falk@sun.com In the future, somebody will quote Andy Warhol every 15 minutes.