Browse Prior Art Database

High Quality Color Image Display with Small Palettes

IP.com Disclosure Number: IPCOM000104654D
Original Publication Date: 1993-May-01
Included in the Prior Art Database: 2005-Mar-19
Document File: 2 page(s) / 80K

Publishing Venue

IBM

Related People

McFall, JD: AUTHOR [+2]

Abstract

A typical personal computer has a color monitor and display adapter which can handle 256 colours simultaneously, chosen from a set of about 256,000 colors. Such a set of 256 colors constitute a "palette". A window manager, such as the IBM OS/2* Presentation Manager* (PM), establishes a default or system palette which is then used by all applications. An application specifies a color to PM which PM then maps into the system palette. In the case of PM, the mapping is fast but rudimentary, resulting in severe contouring and colour distortion when a natural photo-realistic image is displayed. A more careful simulation of desired colors is required; there are many well-known techniques available to do this.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

High Quality Color Image Display with Small Palettes

      A typical personal computer has a color monitor and display
adapter which can handle 256 colours simultaneously, chosen from a
set of about 256,000 colors.  Such a set of 256 colors constitute a
"palette".  A window manager, such as the IBM OS/2* Presentation
Manager* (PM), establishes a default or system palette which is then
used by all applications.  An application specifies a color to PM
which PM then maps into the system palette.  In the case of PM, the
mapping is fast but rudimentary, resulting in severe contouring and
colour distortion when a natural photo-realistic image is displayed.
A more careful simulation of desired colors is required; there are
many well-known techniques available to do this.  The following
paragraphs explain how to work within a window environment such as PM
in order to use sophisticated color simulation algorithms.

      In the case of PM, the system palette is obtained by specifying
certain intensities for each phosphor (red, green and blue), along
with a range of values for which each intensity will be substituted.
The palette is built up by taking all combinations of intensities for
the phosphors.  For example, if there are 7 intensities for the red
phosphor, 8 for the green and 4 for the blue phosphor then taking
combinations yields 224 colors.  The palette is filled out with 32
intensities for gray shades (obtained by setting the three phosphor
intensities to the same value).  Again, there are ranges of
intensities associated with each gray palette color, for which the
palette color will be substituted at display time.

      An application specifies a color by specifying intensities for
the various phosphors, typically using one byte for each phosphor.
PM determines into which range each intensity falls and then uses the
appropriate intensity for that range.  Gray colors are detected and
again PM determines into which range the intensity falls and then
uses the palette colour for that range.  This lends itself to a very
simple implementation which is very fast.

      An important device provided by PM for applications is the...