glPixelMapusv function

Article
12/11/2020

The glPixelMapusv function sets up pixel transfer maps.

Syntax

void WINAPI glPixelMapusv(
         GLenum   map,
         GLsizei  mapsize,
   const GLushort *values
);

Parameters

map

A symbolic map name. The ten maps are as follows.

Value	Meaning
GL_PIXEL_MAP_I_TO_I	Maps color indexes to color indexes.
GL_PIXEL_MAP_S_TO_S	Maps stencil indexes to stencil indexes.
GL_PIXEL_MAP_I_TO_R	Maps color indexes to red components.
GL_PIXEL_MAP_I_TO_G	Maps color indexes to green components.
GL_PIXEL_MAP_I_TO_B	Maps color indexes to blue components.
GL_PIXEL_MAP_I_TO_A	Maps color indexes to alpha components.
GL_PIXEL_MAP_R_TO_R	Maps red components to red components.
GL_PIXEL_MAP_G_TO_G	Maps green components to green components.
GL_PIXEL_MAP_B_TO_B	Maps blue components to blue components.
GL_PIXEL_MAP_A_TO_A	Maps alpha components to alpha components.

mapsize

The size of the map being defined.

values

An array of mapsize values.

Return value

This function does not return a value.

Error codes

The following error codes can be retrieved by the glGetError function.

Name	Meaning
GL_INVALID_ENUM	map was not an accepted value.
GL_INVALID_VALUE	mapsize was negative or larger than GL_PIXEL_MAP_TABLE.
GL_INVALID_VALUE	map was GL_PIXEL_MAP_I_TO_I, GL_PIXEL_MAP_S_TO_S, GL_PIXEL_MAP_I_TO_R, GL_PIXEL_MAP_I_TO_G, GL_PIXEL_MAP_I_TO_B, or GL_PIXEL_MAP_I_TO_A, and mapsize was not a power of two.
GL_INVALID_OPERATION	The function was called between a call to glBegin and the corresponding call to glEnd.

Remarks

The glPixelMap function sets up translation tables, or maps, used by glCopyPixels, glCopyTexImage1D, glCopyTexImage2D, glCopyTexSubImage1D, glCopyTexSubImage2D, glDrawPixels, glReadPixels, glTexImage1D, glTexImage2D, glTexSubImage1D, and glTexSubImage2D. Use of these maps is described completely in the glPixelTransfer topic, and partly in the topics for the pixel and texture image commands. Only the specification of the maps is described in this topic.

The map parameter is a symbolic map name, indicating one of ten maps to set. The mapsize parameter specifies the number of entries in the map, and values is a pointer to an array of mapsize map values.

The entries in a map can be specified as single-precision floating-point numbers, unsigned short integers, or unsigned long integers. Maps that store color component values (all but GL_PIXEL_MAP_I_TO_I and GL_PIXEL_MAP_S_TO_S) retain their values in floating-point format, with unspecified mantissa and exponent sizes. Floating-point values specified by glPixelMapfv are converted directly to the internal floating-point format of these maps, and then clamped to the range [0,1]. Unsigned integer values specified by glPixelMapusv and glPixelMapuiv are converted linearly such that the largest representable integer maps to 1.0, and zero maps to 0.0.

Maps that store indexes, GL_PIXEL_MAP_I_TO_I and GL_PIXEL_MAP_S_TO_S, retain their values in fixed-point format, with an unspecified number of bits to the right of the binary point. Floating-point values specified by glPixelMapfv are converted directly to the internal fixed-point format of these maps. Unsigned integer values specified by glPixelMapusv and glPixelMapuiv specify integer values, with all zeros to the right of the binary point.

The following table shows the initial sizes and values for each of the maps. Maps that are indexed by either color or stencil indexes must have mapsize = 2 ^ n for some n or results are undefined. The maximum allowable size for each map depends on the implementation and can be determined by calling glGet with argument GL_MAX_PIXEL_MAP_TABLE. The single maximum applies to all maps, and it is at least 32.

Map	Lookup Index	Lookup Value	Initial Size
GL_PIXEL_MAP_I_TO_I	color index	color index	1
GL_PIXEL_MAP_S_TO_S	stencil index	stencil index	1
GL_PIXEL_MAP_I_TO_R	color index	R	1
GL_PIXEL_MAP_I_TO_G	color index	G	1
GL_PIXEL_MAP_I_TO_B	color index	B	1
GL_PIXEL_MAP_I_TO_A	color index	A	1
GL_PIXEL_MAP_R_TO_R	R	R	1
GL_PIXEL_MAP_G_TO_G	G	G	1
GL_PIXEL_MAP_B_TO_B	B	B	1
GL_PIXEL_MAP_A_TO_A	A	A	1

The following functions retrieve information related to glPixelMap:

glGet with argument GL_PIXEL_MAP_I_TO_I_SIZE

glGet with argument GL_PIXEL_MAP_S_TO_S_SIZE

glGet with argument GL_PIXEL_MAP_I_TO_R_SIZE

glGet with argument GL_PIXEL_MAP_I_TO_G_SIZE

glGet with argument GL_PIXEL_MAP_I_TO_B_SIZE

glGet with argument GL_PIXEL_MAP_I_TO_A_SIZE

glGet with argument GL_PIXEL_MAP_R_TO_R_SIZE

glGet with argument GL_PIXEL_MAP_G_TO_G_SIZE

glGet with argument GL_PIXEL_MAP_B_TO_B_SIZE

glGet with argument GL_PIXEL_MAP_A_TO_A_SIZE

glGet with argument GL_MAX_PIXEL_MAP_TABLE

Requirements

Requirement	Value
Minimum supported client	Windows 2000 Professional [desktop apps only]
Minimum supported server	Windows 2000 Server [desktop apps only]
Header	Gl.h
Library	Opengl32.lib
DLL	Opengl32.dll

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