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
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.


SEE ALSO
     glHistogramEXT, glResetHistogramEXT, glGetHistogramParameterEXT.