Pixel lookup in multiple variably-sized hardware virtual colormaps in a computer video graphics system
US5025249A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jun 13, 1988 |
| Grant date | Jun 18, 1991 |
| Priority date | — |
| Expiry date | Jun 13, 2008 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG09G5/14
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
This invention adds a window dependent base value to the pixel values read from a frame buffer or other source of pixel values. The base value points to the base of the colormap for that window, which is allocated within a larger, physical colormap. Each window can access physical colormap entries starting at its base value and extending up to the base value plus the maximum pixel value used in that window. Adding a window dependent base value to the pixel values for each window allows different windows to use different colormaps, each of which can be allocated to any contiguous set of entries in the physical colormap. Each window's virtual colormap need only use as many entries in the physical colormap as there are entries in the virtual colormap. Finally, virtual colormaps can be compacted or otherwise reallocated in the physical colormap without requiring changes in the pixel values stored in the frame buffer. Only the colormap base values stored for each window need be changed.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.