Browse Prior Art Database

Linearized 16-bit Color

IP.com Disclosure Number: IPCOM000106903D
Original Publication Date: 1992-Jan-01
Included in the Prior Art Database: 2005-Mar-21
Document File: 4 page(s) / 176K

Publishing Venue

IBM

Related People

West, RMP: AUTHOR

Abstract

Disclosed is a simple and efficient means by which 16-bit Direct Color data can be mapped linearly to 24-bit Color for display by three 8-bit DACs over the full color range. Full intensity white and zero intensity black can be displayed, with minimum color distortion in the mapping of any intermediate color.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 35% of the total text.

Linearized 16-bit Color

       Disclosed is a simple and efficient means by which 16-bit
Direct Color data can be mapped linearly to 24-bit Color for display
by three 8-bit DACs over the full color range.  Full intensity white
and zero intensity black can be displayed, with minimum color
distortion in the mapping of any intermediate color.

      The method finds application in the field of computer graphics,
particularly in the arena of Personal Systems, and is relevant to
display adapters, computer graphics systems, or VLSI components
therein.  It could be added as a standard feature to any future chip
designs or simply retro-fitted to current modules to enhance their
function.

      When 2 bytes (16 bits) are allocated to each pixel to represent
its color, it is common that some form of Direct Color representation
is used.  The 16 bits are divided up between the three primary colors
in equal manner.  Forms of Direct Color found in current graphics
products are:
565RGB - 5 Red, 6 Green, 5 Blue;  664RGB - 6 Red, 6 Green, 4
Blue; 555RGB - 5 Red, 5 Green, 5 Blue + 1 center bit.

      The disclosure is applicable to any such color coding scheme,
but concentrates on 565RGB since this is found in current IBM
graphics products.  565RGB is used to illustrate the problem,
existing solutions, their deficiencies, and the disclosed solution.
The disclosure also concentrates on DACs of 8-bit resolution, but is
applicable to DACs of any other resolution that is greater than the
number of bits of data available for each primary color.  Variations
and extensions to different numbers of bits per pixel, to different
Direct Color coding schemes, and to DACs of different resolutions
will be apparent to those skilled in the art.

      565RGB 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.
With 16- bit Direct Color, it can define 32 x 64 x 32 = 65536
different colors.

      The 8-bit DACs allow 256 different intensity values to be
displayed for each primary color.  Because of the nature of DACs, the
displayed intensity values are linearly ascending, with all bits zero
yielding the minimum (0) intensity and all bits one yielding the
maximum (255) intensity for each primary color.  When all three DACs
are at minimum (0) intensity, the resulting displayed color is zero
intensity black.   When all three DACs are at maximum (255)
intensity, the resulting displayed color is full intensi...