glMinmax — define minmax table
void glMinmax( | GLenum | target, |
| GLenum | internalformat, | |
| GLboolean | sink); |
target
The minmax table whose parameters are to be set.
Must be
GL_MINMAX.
internalformat
The format of entries in the minmax table.
Must be one of
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_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, or
GL_RGBA16.
sink
If GL_TRUE, pixels will be consumed by the minmax
process and no drawing or texture loading will take place.
If GL_FALSE, pixels will proceed to the final conversion process after
minmax.
When GL_MINMAX is enabled, the RGBA components of incoming pixels are
compared to the minimum and maximum values for each component, which are
stored in the two-element minmax table.
(The first element stores the minima, and the second element stores
the maxima.)
If a pixel component is greater than the corresponding component
in the maximum element, then the maximum element is updated with the
pixel component value.
If a pixel component is less than the corresponding component in
the minimum element, then the minimum element is updated with the
pixel component value.
(In both cases, if the internal format of the minmax table includes
luminance, then the R color component of incoming pixels is used
for comparison.)
The contents of the minmax table may be retrieved at a later time
by calling glGetMinmax.
The minmax operation is enabled or disabled by calling glEnable or
glDisable, respectively, with an argument of GL_MINMAX.
glMinmax redefines the current minmax table to have entries of the format
specified by internalformat.
The maximum element is initialized with the smallest possible component
values, and the minimum element is initialized with the largest possible
component values.
The values in the previous minmax table, if any, are lost.
If sink is GL_TRUE, then pixels are discarded after minmax;
no further processing of the pixels takes place, and no drawing,
texture loading, or pixel readback will result.
glMinmax is present only if ARB_imaging is returned when glGetString
is called with an argument of GL_EXTENSIONS.
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_OPERATION is generated if glMinmax is executed
between the execution of glBegin and the corresponding
execution of glEnd.
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/.