glgethistogramext
- Man Page
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 GL_HISTOGRAM_EXT.
reset If GL_TRUE, each component counter that is actually returned is
reset to zero. (Other counters are unaffected.) If GL_FALSE,
none of the counters in the histogram table is modified.
format The format of values to be returned in values. Must be one of
GL_RED, GL_GREEN, GL_BLUE, GL_ALPHA, GL_RGB, GL_RGBA,
GL_ABGR_EXT, GL_LUMINANCE, or GL_LUMINANCE_ALPHA.
type The type of values to be returned in values. Must be one of
GL_UNSIGNED_BYTE, GL_BYTE, GL_UNSIGNED_SHORT, GL_SHORT,
GL_UNSIGNED_INT, GL_INT, GL_FLOAT, GL_UNSIGNED_BYTE_3_3_2_EXT,
GL_UNSIGNED_SHORT_4_4_4_4_EXT, GL_UNSIGNED_SHORT_5_5_5_1_EXT,
GL_UNSIGNED_INT_8_8_8_8_EXT, or GL_UNSIGNED_INT_10_10_10_2_EXT.
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
Page 1
glGetHistogramEXT(3G) OpenGL Reference glGetHistogramEXT(3G)
ERRORS
GL_INVALID_ENUM is generated if target is not GL_HISTOGRAM_EXT.
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_OPERATION is generated if glGetHistogramEXT is executed
between the execution of glBegin and the corresponding execution of
glEnd.
If type is set to GL_UNSIGNED_BYTE_3_3_2_EXT,
GL_UNSIGNED_SHORT_4_4_4_4_EXT, GL_UNSIGNED_SHORT_5_5_5_1_EXT,
GL_UNSIGNED_INT_8_8_8_8_EXT, or GL_UNSIGNED_INT_10_10_10_2_EXT and the
EXT_packed_pixels extension is not supported then a GL_INVALID_ENUM error
is generated.
MACHINE DEPENDENCIES
On RealityEngine, RealityEngine2, and VTX systems, histogram and minmax
may not be used when rendering to pixmaps.
On InfiniteReality systems selection and histogramming are unreliable if
interrupted by a graphics context switch. This will be fixed in the next
software release.
SEE ALSO
glHistogramEXT, glResetHistogramEXT, glGetHistogramParameterEXT.
Page 2