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glPixelMap

Chapter 14

325

GL_PIXEL_MAP_I_TO_R

Maps color indices to red components.

GL_PIXEL_MAP_I_TO_G

Maps color indices to green components.

GL_PIXEL_MAP_I_TO_B

Maps color indices to blue components.

GL_PIXEL_MAP_I_TO_A

Maps color indices 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.

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, 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 0 maps to 0.0.

Maps that store indices, 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 0s 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 indices must have mapsize = 2

for some n or the

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; it is at least

32.

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