glGetHistogramEXT(3G) OpenGL Reference glGetHistogramEXT(3G)
NAME
glGetHistogramEXT - get histogram table
C SPECIFICATION
void glGetHistogramEXT( GLenum target,
GLboolean reset,
GLenum format,
GLenum type,
GLvoid *values )
PARAMETERS
target Must be GLHISTOGRAMEXT.
reset If GLTRUE, each component counter that is actually returned is
reset to zero. (Other counters are unaffected.) If GLFALSE,
none of the counters in the histogram table is modified.
format The format of values to be returned in values. Must be one of
GLRED, GLGREEN, GLBLUE, GLALPHA, GLRGB, GLRGBA,
GLABGREXT, GLLUMINANCE, or GLLUMINANCEALPHA.
type The type of values to be returned in values. Must be one of
GLUNSIGNEDBYTE, GLBYTE, GLUNSIGNEDSHORT, GLSHORT,
GLUNSIGNEDINT, GLINT, GLFLOAT, GLUNSIGNEDBYTE332EXT,
GLUNSIGNEDSHORT4444EXT, GLUNSIGNEDSHORT5551EXT,
GLUNSIGNEDINT8888EXT, or GLUNSIGNEDINT1010102EXT.
values A pointer to storage for the returned histogram table.
DESCRIPTION
glGetHistogramEXT returns the current histogram table as a one-
dimensional image with the same width as the histogram. No pixel
transfer operations are performed on this image, but pixel storage modes
that are applicable to 1D images are honored.
Color components that are requested in the specified format, but which
are not included in the internal format of the histogram, are returned as
zero. The assignments of internal color components to the components
requested by format are:
Internal Component Result Component
_____________________________________
red red
green green
blue blue
alpha alpha
luminance red
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glGetHistogramEXT(3G) OpenGL Reference glGetHistogramEXT(3G)
ERRORS
GLINVALIDENUM is generated if target is not GLHISTOGRAMEXT.
GLINVALIDENUM is generated if format is not one of the allowable
values.
GLINVALIDENUM is generated if type is not one of the allowable values.
GLINVALIDOPERATION is generated if glGetHistogramEXT is executed
between the execution of glBegin and the corresponding execution of
glEnd.
If type is set to GLUNSIGNEDBYTE332EXT,
GLUNSIGNEDSHORT4444EXT, GLUNSIGNEDSHORT5551EXT,
GLUNSIGNEDINT8888EXT, or GLUNSIGNEDINT1010102EXT and the
EXTpackedpixels extension is not supported then a GLINVALIDENUM error
is generated.
MACHINE DEPENDENCIES
On RealityEngine, RealityEngine2, and VTX systems, histogram and minmax
may not be used when rendering to pixmaps.
SEE ALSO
glHistogramEXT, glResetHistogramEXT, glGetHistogramParameterEXT.
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