glColorTable man page on RedHat
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GLCOLORTABLE(3G) OpenGL Manual GLCOLORTABLE(3G)
NAME
glColorTable - define a color lookup table
C SPECIFICATION
void glColorTable(GLenum target, GLenum internalformat, GLsizei width,
GLenum format, GLenum type, const GLvoid * data);
PARAMETERS
target
Must be one of GL_COLOR_TABLE, GL_POST_CONVOLUTION_COLOR_TABLE,
GL_POST_COLOR_MATRIX_COLOR_TABLE, GL_PROXY_COLOR_TABLE,
GL_PROXY_POST_CONVOLUTION_COLOR_TABLE, or
GL_PROXY_POST_COLOR_MATRIX_COLOR_TABLE.
internalformat
The internal format of the color table. The allowable values are
GL_ALPHA, GL_ALPHA4, GL_ALPHA8, GL_ALPHA12, GL_ALPHA16,
GL_LUMINANCE, GL_LUMINANCE4, GL_LUMINANCE8, GL_LUMINANCE12,
GL_LUMINANCE16, GL_LUMINANCE_ALPHA, GL_LUMINANCE4_ALPHA4,
GL_LUMINANCE6_ALPHA2, GL_LUMINANCE8_ALPHA8, GL_LUMINANCE12_ALPHA4,
GL_LUMINANCE12_ALPHA12, GL_LUMINANCE16_ALPHA16, GL_INTENSITY,
GL_INTENSITY4, GL_INTENSITY8, GL_INTENSITY12, GL_INTENSITY16,
GL_R3_G3_B2, GL_RGB, GL_RGB4, GL_RGB5, GL_RGB8, GL_RGB10, GL_RGB12,
GL_RGB16, GL_RGBA, GL_RGBA2, GL_RGBA4, GL_RGB5_A1, GL_RGBA8,
GL_RGB10_A2, GL_RGBA12, and GL_RGBA16.
width
The number of entries in the color lookup table specified by data.
format
The format of the pixel data in data. The allowable values are
GL_RED, GL_GREEN, GL_BLUE, GL_ALPHA, GL_LUMINANCE,
GL_LUMINANCE_ALPHA, GL_RGB, GL_BGR, GL_RGBA, and GL_BGRA.
type
The type of the pixel data in data. The allowable values are
GL_UNSIGNED_BYTE, GL_BYTE, GL_UNSIGNED_SHORT, GL_SHORT,
GL_UNSIGNED_INT, GL_INT, GL_FLOAT, GL_UNSIGNED_BYTE_3_3_2,
GL_UNSIGNED_BYTE_2_3_3_REV, GL_UNSIGNED_SHORT_5_6_5,
GL_UNSIGNED_SHORT_5_6_5_REV, GL_UNSIGNED_SHORT_4_4_4_4,
GL_UNSIGNED_SHORT_4_4_4_4_REV, GL_UNSIGNED_SHORT_5_5_5_1,
GL_UNSIGNED_SHORT_1_5_5_5_REV, GL_UNSIGNED_INT_8_8_8_8,
GL_UNSIGNED_INT_8_8_8_8_REV, GL_UNSIGNED_INT_10_10_10_2, and
GL_UNSIGNED_INT_2_10_10_10_REV.
data
Pointer to a one-dimensional array of pixel data that is processed
to build the color table.
DESCRIPTION
glColorTable may be used in two ways: to test the actual size and color
resolution of a lookup table given a particular set of parameters, or
to load the contents of a color lookup table. Use the targets
GL_PROXY_* for the first case and the other targets for the second
case.
If a non-zero named buffer object is bound to the
GL_PIXEL_UNPACK_BUFFER target (see glBindBuffer()) while a color table
is specified, data is treated as a byte offset into the buffer object's
data store.
If target is GL_COLOR_TABLE, GL_POST_CONVOLUTION_COLOR_TABLE, or
GL_POST_COLOR_MATRIX_COLOR_TABLE, glColorTable builds a color lookup
table from an array of pixels. The pixel array specified by width,
format, type, and data is extracted from memory and processed just as
if glDrawPixels() were called, but processing stops after the final
expansion to RGBA is completed.
The four scale parameters and the four bias parameters that are defined
for the table are then used to scale and bias the R, G, B, and A
components of each pixel. (Use glColorTableParameter to set these scale
and bias parameters.)
Next, the R, G, B, and A values are clamped to the range 0 1. Each
pixel is then converted to the internal format specified by
internalformat. This conversion simply maps the component values of the
pixel (R, G, B, and A) to the values included in the internal format
(red, green, blue, alpha, luminance, and intensity). The mapping is as
follows:
┌─────────────────────────────────┬─────────────────────────────┬───────────────────────────────┬──────────────────────────────┬───────────────────────────────┬───────────────────────────────────┬───────────────────────────────────┐
│ │ │ │ │ │ │ │
│ Internal │ Red │ Green │ Blue │ Alpha │ Luminance │ Intensity │
│Format │ │ │ │ │ │ │
│ │ │ │ │ │ │ │
├─────────────────────────────────┼─────────────────────────────┼───────────────────────────────┼──────────────────────────────┼───────────────────────────────┼───────────────────────────────────┼───────────────────────────────────┤
│GL_ALPHA │ │ │ │ A │ │ │
├─────────────────────────────────┼─────────────────────────────┼───────────────────────────────┼──────────────────────────────┼───────────────────────────────┼───────────────────────────────────┼───────────────────────────────────┤
│GL_LUMINANCE │ │ │ │ │ R │ │
├─────────────────────────────────┼─────────────────────────────┼───────────────────────────────┼──────────────────────────────┼───────────────────────────────┼───────────────────────────────────┼───────────────────────────────────┤
│GL_LUMINANCE_ALPHA │ │ │ │ A │ R │ │
├─────────────────────────────────┼─────────────────────────────┼───────────────────────────────┼──────────────────────────────┼───────────────────────────────┼───────────────────────────────────┼───────────────────────────────────┤
│GL_INTENSITY │ │ │ │ │ │ R │
├─────────────────────────────────┼─────────────────────────────┼───────────────────────────────┼──────────────────────────────┼───────────────────────────────┼───────────────────────────────────┼───────────────────────────────────┤
│GL_RGB │ R │ G │ B │ │ │ │
├─────────────────────────────────┼─────────────────────────────┼───────────────────────────────┼──────────────────────────────┼───────────────────────────────┼───────────────────────────────────┼───────────────────────────────────┤
│GL_RGBA │ R │ G │ B │ A │ │ │
└─────────────────────────────────┴─────────────────────────────┴───────────────────────────────┴──────────────────────────────┴───────────────────────────────┴───────────────────────────────────┴───────────────────────────────────┘
Finally, the red, green, blue, alpha, luminance, and/or intensity
components of the resulting pixels are stored in the color table. They
form a one-dimensional table with indices in the range 0 width - 1.
If target is GL_PROXY_*, glColorTable recomputes and stores the values
of the proxy color table's state variables GL_COLOR_TABLE_FORMAT,
GL_COLOR_TABLE_WIDTH, GL_COLOR_TABLE_RED_SIZE,
GL_COLOR_TABLE_GREEN_SIZE, GL_COLOR_TABLE_BLUE_SIZE,
GL_COLOR_TABLE_ALPHA_SIZE, GL_COLOR_TABLE_LUMINANCE_SIZE, and
GL_COLOR_TABLE_INTENSITY_SIZE. There is no effect on the image or state
of any actual color table. If the specified color table is too large to
be supported, then all the proxy state variables listed above are set
to zero. Otherwise, the color table could be supported by glColorTable
using the corresponding non-proxy target, and the proxy state variables
are set as if that target were being defined.
The proxy state variables can be retrieved by calling
glGetColorTableParameter() with a target of GL_PROXY_*. This allows the
application to decide if a particular glColorTable command would
succeed, and to determine what the resulting color table attributes
would be.
If a color table is enabled, and its width is non-zero, then its
contents are used to replace a subset of the components of each RGBA
pixel group, based on the internal format of the table.
Each pixel group has color components (R, G, B, A) that are in the
range 0.0 1.0. The color components are rescaled to the size of the
color lookup table to form an index. Then a subset of the components
based on the internal format of the table are replaced by the table
entry selected by that index. If the color components and contents of
the table are represented as follows:
┌───────────────────────────────────────┬─────────────────────────────────┐
│ │ │
│ Representation │ Meaning │
│ │ │
├───────────────────────────────────────┼─────────────────────────────────┤
│ r │ Table index computed from R │
├───────────────────────────────────────┼─────────────────────────────────┤
│ g │ Table index computed from G │
├───────────────────────────────────────┼─────────────────────────────────┤
│ b │ Table index computed from B │
├───────────────────────────────────────┼─────────────────────────────────┤
│ a │ Table index computed from A │
├───────────────────────────────────────┼─────────────────────────────────┤
│ L[i] │ Luminance value at table index │
│ │ i │
├───────────────────────────────────────┼─────────────────────────────────┤
│ I[i] │ Intensity value at table index │
│ │ i │
├───────────────────────────────────────┼─────────────────────────────────┤
│ R[i] │ Red value at table index i │
├───────────────────────────────────────┼─────────────────────────────────┤
│ G[i] │ Green value at table index i │
├───────────────────────────────────────┼─────────────────────────────────┤
│ B[i] │ Blue value at table index i │
├───────────────────────────────────────┼─────────────────────────────────┤
│ A[i] │ Alpha value at table index i │
└───────────────────────────────────────┴─────────────────────────────────┘
then the result of color table lookup is as follows:
┌──────────────────────────────┬───────────────────────────────────────────────────────────────────────────────────────────────────────────────┐
│ │ │
│ │ Resulting Texture Components │
│ │ │
├──────────────────────────────┼───────────────────────────┬───────────────────────────┬───────────────────────────┬───────────────────────────┤
│ │ │ │ │ │
│ Table │ R │ G │ B │ A │
│Internal │ │ │ │ │
│Format │ │ │ │ │
│ │ │ │ │ │
├──────────────────────────────┼───────────────────────────┼───────────────────────────┼───────────────────────────┼───────────────────────────┤
│GL_ALPHA │ R │ G │ B │ A[a] │
├──────────────────────────────┼───────────────────────────┼───────────────────────────┼───────────────────────────┼───────────────────────────┤
│GL_LUMINANCE │ L[r] │ L[g] │ L[b] │ At │
├──────────────────────────────┼───────────────────────────┼───────────────────────────┼───────────────────────────┼───────────────────────────┤
│GL_LUMINANCE_ALPHA │ L[r] │ L[g] │ L[b] │ A[a] │
├──────────────────────────────┼───────────────────────────┼───────────────────────────┼───────────────────────────┼───────────────────────────┤
│GL_INTENSITY │ I[r] │ I[g] │ I[b] │ I[a] │
├──────────────────────────────┼───────────────────────────┼───────────────────────────┼───────────────────────────┼───────────────────────────┤
│GL_RGB │ R[r] │ G[g] │ B[b] │ A │
├──────────────────────────────┼───────────────────────────┼───────────────────────────┼───────────────────────────┼───────────────────────────┤
│GL_RGBA │ R[r] │ G[g] │ B[b] │ A[a] │
└──────────────────────────────┴───────────────────────────┴───────────────────────────┴───────────────────────────┴───────────────────────────┘
When GL_COLOR_TABLE is enabled, the colors resulting from the pixel map
operation (if it is enabled) are mapped by the color lookup table
before being passed to the convolution operation. The colors resulting
from the convolution operation are modified by the post convolution
color lookup table when GL_POST_CONVOLUTION_COLOR_TABLE is enabled.
These modified colors are then sent to the color matrix operation.
Finally, if GL_POST_COLOR_MATRIX_COLOR_TABLE is enabled, the colors
resulting from the color matrix operation are mapped by the post color
matrix color lookup table before being used by the histogram operation.
NOTES
glColorTable is present only if ARB_imaging is returned when
glGetString() is called with an argument of GL_EXTENSIONS.
If target is set to GL_COLOR_TABLE, GL_POST_CONVOLUTION_COLOR_TABLE, or
GL_POST_COLOR_MATRIX_COLOR_TABLE, then width must be a power of two or
a GL_INVALID_VALUE error is generated.
ERRORS
GL_INVALID_ENUM is generated if target is not one of the allowable
values.
GL_INVALID_ENUM is generated if internalformat is not one of the
allowable values.
GL_INVALID_ENUM is generated if format is not one of the allowable
values.
GL_INVALID_ENUM is generated if type is not one of the allowable
values.
GL_INVALID_VALUE is generated if width is less than zero.
GL_TABLE_TOO_LARGE is generated if the requested color table is too
large to be supported by the implementation, and target is not a
GL_PROXY_* target.
GL_INVALID_OPERATION is generated if a non-zero buffer object name is
bound to the GL_PIXEL_UNPACK_BUFFER target and the buffer object's data
store is currently mapped.
GL_INVALID_OPERATION is generated if a non-zero buffer object name is
bound to the GL_PIXEL_UNPACK_BUFFER target and the data would be
unpacked from the buffer object such that the memory reads required
would exceed the data store size.
GL_INVALID_OPERATION is generated if a non-zero buffer object name is
bound to the GL_PIXEL_UNPACK_BUFFER target and data is not evenly
divisible into the number of bytes needed to store in memory a datum
indicated by type.
GL_INVALID_OPERATION is generated if glColorTable is executed between
the execution of glBegin() and the corresponding execution of glEnd().
ASSOCIATED GETS
glGetColorTableParameter()
glGet() with argument GL_PIXEL_UNPACK_BUFFER_BINDING
SEE ALSO
glColorSubTable(), glColorTableParameter, glCopyColorTable(),
glCopyColorSubTable(), glGetColorTable()
COPYRIGHT
Copyright © 1991-2006 Silicon Graphics, Inc. This document is licensed
under the SGI Free Software B License. For details, see
http://oss.sgi.com/projects/FreeB/.
AUTHORS
opengl.org
opengl.org 03/16/2013 GLCOLORTABLE(3G)
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