okeefe@cs.Buffalo.EDU (Paul O'Keefe) (03/05/91)
I need some help understanding the relationship between image depth and colormaps in apE. I using apE on a SparcStation with an 8-bit color X11 server. This machine also has a Taac board which has 24-bit color. I was hoping to export apE images as 24-bit Sun rasterfiles then import them into Taac format and see them in true color. I beleive that apE is able to generate true color images since: 1) the apE function "img_export" can output a apE image in numerous formats including 24-bit Sun rasterfiles 2) the image produced by Comer Duncan and shown in Pixel Magazine certainly appeared to be true color. However, the apE manual says that all colormaps have 245 entries. Question: how does this jive? Is the image computed in true-color and the 8-bit colormap is just a subset used for display within apE? Paul O'Keefe okeefe@cs.buffalo.edu
anderson@osc.edu (Steve Anderson) (03/05/91)
In article <1991Mar4.185030@cs.Buffalo.EDU>, okeefe@cs.Buffalo.EDU (Paul O'Keefe) writes: > > > I need some help understanding the relationship between > image depth and colormaps in apE. > > I using apE on a SparcStation with an 8-bit color X11 server. > This machine also has a Taac board which has 24-bit color. > I was hoping to export apE images as 24-bit Sun rasterfiles > then import them into Taac format and see them in true color. > > However, the apE manual says that all colormaps have 245 entries. > > Question: how does this jive? > > Is the image computed in true-color and the 8-bit colormap is just > a subset used for display within apE? > > Paul O'Keefe > okeefe@cs.buffalo.edu correct. Images are (can be) computed and maintained in 24-bits, with dithering happening at display time to the "best representation" on the hardware. apE colormaps are commonly used when you want to limit the number of colors; applying a colormap when computing the image, instead of using full-color. Images rendered using colormaps can be manipulated and displayed much faster (obviously). apE colormaps are 245 elements because they had to be slightly smaller than 256 to allow usefullness in window systems which reserve several slots. We also keep the interface colors outside of the 245, so there is less flashing of windows as the colormaps come in and out of the system. For dithering, there is a "default colormap" which has a dither palette in the 245 colormap elements. --steve -- H. Stephen Anderson | email: anderson@osgp.osc.edu The Ohio Supercomputer Graphics Project | Phone: (614) 292-3274 1224 Kinnear Road | Columbus, Ohio 43212 |