Browse Prior Art Database

Enhanced 16-Bit Direct Color for Natural Images

IP.com Disclosure Number: IPCOM000115971D
Original Publication Date: 1995-Jul-01
Included in the Prior Art Database: 2005-Mar-30

Publishing Venue

IBM

Related People

Rackley, DP: AUTHOR [+2]

Abstract

Disclosed is a simple and efficient method for enhancing 16-bit Direct Color data for Natural Images in the conversion to 24-bit Color for display on a system having three 8-bit Digital to Analog Convertors (DACs). The disclosed technique provides Natural Image display quality that is superior to conventional 16 bit-per-pixel Direct Color, by allowing the 16-bit display data to fully utilize the 24-bit display capability of the display subsystem.

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Enhanced 16-Bit Direct Color for Natural Images

      Disclosed is a simple and efficient method for enhancing 16-bit
Direct Color data for Natural Images in the conversion to 24-bit
Color for display on a system having three 8-bit Digital to Analog
Convertors (DACs).  The disclosed technique provides Natural Image
display quality that is superior to conventional 16 bit-per-pixel
Direct Color, by allowing the 16-bit display data to fully utilize
the 24-bit display capability of the display subsystem.

      In the field of MultiMedia, the display of Natural Images
requires a large number of data bits per displayed pixel to achieve
excellent "front of screen" display quality.  Ideally, with a display
subsystem having three 8- bit DACs, the display data for Natural
Images should have 24 bits per pixel to fully utilize the display
capabilities of the subsystem.  However, when encoded as 24
bit-per-pixel data, a Natural Image requires large amounts of storage
and display memory.  As a compromise, Natural Images are often
encoded as 16 bit-per-pixel data, which is probably the minimum
necessary to produce acceptable "front of screen" display quality.

      The presently described method is applied to MultiMedia display
subsystems, and to computer graphic display subsystems, including
extensions and enhancements to the IBM*PS/2* (eXtended Graphics

Adapter (XGA*) display adapters.  This method is applicable to any
display adapter used in a MultiMedia system or subsystem, or to any
display subsystem used for the display of Natural Images.  For
example, this method may be used in the Serializer Palette DAC (SPD)
portion of a display subsystem.  This method can be added as a
standard feature to a future SPD chip design or retro-fitted to
current SPD chip designs to enhance their function.

      When 2 bytes (16 bits) are allocated to each pixel to represent
its color, a form of "Direct Color" representation is commonly used.
In general, the 16 bits are divided among the three primary colors in
a roughly equal manner.  In current graphics products, the bits for
Direct Color are divided among divided among the primary colors in
the following ways:
  565RGB - 5 Red, 6 Green, 5 Blue
  664RGB - 6 Red, 6 Green, 4 Blue
  555RGB - 5 Red, 5 Green, 5 Blue + 1 control bit

      For example, the 565RGB designation means that, of the 16 bits
used to represent each pixel, the first 5 bits are used as the Red
component, the next 6 bits as the Green component, and the last 5
bits are used as the Blue component.  For Red and Blue, there are
five bits of data allowing 32 different intensity values to be
defined for each color.  For Green, there are six bits of data
allowing 64 different color intensity values to be defined.  For
Direct Color, it is usual that the color intensity values are
linearly ascending, with all bits zero yielding the lowest intensity
and all bits one yielding the highest intensity.  Thus, with 16-bit
Direct...