GLGETHISTOGRAM(3G) OpenGL Manual GLGETHISTOGRAM(3G)
NAME
glGetHistogram - get histogram table
C SPECIFICATION
void glGetHistogram(GLenum target, GLboolean reset, GLenum format, GLenum type, GLvoid * values);
PARAMETERS
target
Must be GL_HISTOGRAM.
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_BGR, GL_RGBA, GL_BGRA,
GL_LUMINANCE, or GL_LUMINANCE_ALPHA.
type
The type of values to be returned in values. Symbolic constants GL_UNSIGNED_BYTE, GL_BYTE, GL_BITMAP, GL_UNSIGNED_SHORT, GL_SHORT,
GL_UNSIGNED_INT, GL_INT, GL_FLOAT, GL_UNSIGNED_BYTE_3_3_2, GL_UNSIGNED_BYTE_2_3_3_REV, GL_UNSIGNED_SHORT_5_6_5,
GL_UNSIGNED_SHORT_5_6_5_REV, GL_UNSIGNED_SHORT_4_4_4_4, GL_UNSIGNED_SHORT_4_4_4_4_REV, GL_UNSIGNED_SHORT_5_5_5_1,
GL_UNSIGNED_SHORT_1_5_5_5_REV, GL_UNSIGNED_INT_8_8_8_8, GL_UNSIGNED_INT_8_8_8_8_REV, GL_UNSIGNED_INT_10_10_10_2, and
GL_UNSIGNED_INT_2_10_10_10_REV are accepted.
values
A pointer to storage for the returned histogram table.
DESCRIPTION
glGetHistogram 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.
If a non-zero named buffer object is bound to the GL_PIXEL_PACK_BUFFER target (see glBindBuffer()) while a histogram table is requested,
values is treated as a byte offset into the buffer object's data store.
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 | Resulting Component |
| | |
+-------------------------------------------+---------------------------------------------+
|Red | Red |
+-------------------------------------------+---------------------------------------------+
|Green | Green |
+-------------------------------------------+---------------------------------------------+
|Blue | Blue |
+-------------------------------------------+---------------------------------------------+
|Alpha | Alpha |
+-------------------------------------------+---------------------------------------------+
|Luminance | Red |
+-------------------------------------------+---------------------------------------------+
NOTES
glGetHistogram is present only if ARB_imaging is returned when glGetString() is called with an argument of GL_EXTENSIONS.
ERRORS
GL_INVALID_ENUM is generated if target is not GL_HISTOGRAM.
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 type is one of GL_UNSIGNED_BYTE_3_3_2, GL_UNSIGNED_BYTE_2_3_3_REV, GL_UNSIGNED_SHORT_5_6_5, or
GL_UNSIGNED_SHORT_5_6_5_REV and format is not GL_RGB.
GL_INVALID_OPERATION is generated if type is one of GL_UNSIGNED_SHORT_4_4_4_4, GL_UNSIGNED_SHORT_4_4_4_4_REV, GL_UNSIGNED_SHORT_5_5_5_1,
GL_UNSIGNED_SHORT_1_5_5_5_REV, GL_UNSIGNED_INT_8_8_8_8, GL_UNSIGNED_INT_8_8_8_8_REV, GL_UNSIGNED_INT_10_10_10_2, or
GL_UNSIGNED_INT_2_10_10_10_REV and format is neither GL_RGBA nor GL_BGRA.
GL_INVALID_OPERATION is generated if a non-zero buffer object name is bound to the GL_PIXEL_PACK_BUFFER target and the buffer object's data
store is currently mapped.
GL_INVALID_OPERATION is generated if a non-zero buffer object name is bound to the GL_PIXEL_PACK_BUFFER target and the data would be packed
to the buffer object such that the memory writes required would exceed the data store size.
GL_INVALID_OPERATION is generated if a non-zero buffer object name is bound to the GL_PIXEL_PACK_BUFFER target and values is not evenly
divisible into the number of bytes needed to store in memory a datum indicated by type.
GL_INVALID_OPERATION is generated if glGetHistogram is executed between the execution of glBegin() and the corresponding execution of
glEnd().
ASSOCIATED GETS
glGetHistogramParameter()
glGet() with argument GL_PIXEL_PACK_BUFFER_BINDING
SEE ALSO
glHistogram(), glResetHistogram(),
COPYRIGHT
Copyright (C) 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/.
AUTHORS
opengl.org
opengl.org 06/10/2014 GLGETHISTOGRAM(3G)