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COLOR MAP TECHNIQUES

IP.com Disclosure Number: IPCOM000128621D
Original Publication Date: 1978-Dec-31
Included in the Prior Art Database: 2005-Sep-16
Document File: 15 page(s) / 49K

Publishing Venue

Software Patent Institute

Related People

Kenneth R. Sloan, Jr.: AUTHOR [+4]

Abstract

Full color, raster scan displays are increasingly popular media for computer graphics. Several bits of information about every picture element in a raster image can be stored in a local image memory and used to produce a video display. A color map is a look-up table interposed between the image memory and the video display generator which can be used to implement an arbitrary mapping from image memory values to display values. We present several techniques and applications which depend upon such a color map to provide fast and flexible changes to the display without rewriting the image memory. This work was supported in part by Alfred P. Sloan Foundation grant # 74-12-5 and in part by National Science Foundation grant # MCS76-10825.

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THIS DOCUMENT IS AN APPROXIMATE REPRESENTATION OF THE ORIGINAL.

COLOR MAP TECHNIQUES

Kenneth R. Sloan, Jr. Christopher M. Brown

Computer Science Department University of Rochester

TR 36

June 1978 Revised January 1979

ABSTRACT

Full color, raster scan displays are increasingly popular media for computer graphics. Several bits of information about every picture element in a raster image can be stored in a local image memory and used to produce a video display. A color map is a look-up table interposed between the image memory and the video display generator which can be used to implement an arbitrary mapping from image memory values to display values. We present several techniques and applications which depend upon such a color map to provide fast and flexible changes to the display without rewriting the image memory.

This work was supported in part by Alfred P. Sloan Foundation grant # 74-12-5 and in part by National Science Foundation grant # MCS76-10825.

INTRODUCTION

Full color, raster scan displays are increasingly popular media for computer graphics. As mass memories drop in price, it has become economically feasible to store and display color images at resolutions comparable to standard television sets [Negroponte, 1977]. Typically, the image is represented as a complete array of picture elements (pixels), with each pixel representing a small area of fixed size and position in the image. A pixel, in turn, is represented as a set of bits, usually organized as a set of single-bit "planes." A binary image requires a single-bit plane, which may be interpreted as "Black if 1, White if 0." Where several bits are used, they may be interpreted naturally as a grey-scale intensity or a set of Red, Green, and Blue intensities. In simple hardware configurations, the image memory planes have fixed interpretations; for example, 12 planes may always be interpreted as Red, Green, and Blue intensities of 4 bits (16 levels) each. The interpretation is done by a video display generator which continuously scans the image memory and produces a video signal which is displayed on a monitor (binary, grey- scale, or color). If the selection of bit planes going to the digital-to-analog converters (DAC's) of the video generator is hardwired, the configuration is sometimes called "true color." Color maps provide a way to allocate bit planes flexibly; they include the true color configurations as a special case. Fixed interpretation of the image planes (a true color configuration) is satisfactory for many applications; however, when the images being processed (or created) do not have a "natural" color or intensity, this fixed display mode is unnecessarily restrictive. The pixels may have interpretations such as temperature, or population density; it is often useful to display such data by using color to accentuate the interpretations, calling attention to phenomena of interest. There may be several interesting phenomena, however, and to create a different...