GLGETHISTOGRAM(3G)                                          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 GLHISTOGRAM.

       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   of  values  to  be  returned  in  values.  Must be one of
               GLRED, GLGREN, GLBLUE, GLALPHA, GLRGB,  GLBGR,  GLRGBA,
               GLBGRA, GLUMINANCE, or GLUMINANCEALPHA.

       type    The  type  of  values  to be returned in values.  Symbolic con-
               stants GLUNSIGNEDBYTE, GLBYTE, GLBITMAP, GLUNSIGNEDSHORT,
               GLSHORT,        GLUNSIGNEDINT,       GLINT,       GLFLOAT,
               GLUNSIGNEDBYTE332,             GLUNSIGNEDBYTE233REV,
               GLUNSIGNEDSHORT565,           GLUNSIGNEDSHORT565REV,
               GLUNSIGNEDSHORT4444,       GLUNSIGNEDSHORT4444REV,
               GLUNSIGNEDSHORT5551,       GLUNSIGNEDSHORT1555REV,
               GLUNSIGNEDINT8888,           GLUNSIGNEDINT8888REV,
               GLUNSIGNEDINT1001001002,  and GLUNSIGNEDINT2100100100REV
               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 opera-
       tions 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  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  GLARBimaging  is  returned  when
       glGetString is called with an argument of GLEXTENSIONS.

ERORS
       GLINVALIDENUM is generated if target is not GLHISTOGRAM.

       GLINVALIDENUM is generated if format is not one of the allowable val-
       ues.

       GLINVALIDENUM is generated if type is not one of the  allowable  val-
       ues.

       GLINVALIDOPERATION is generated if glGetHistogram is executed between
       the execution of glBegin and the corresponding execution of glEnd.


       GLINVALIDOPERATION   is    generated    if    type    is    one    of
       GLUNSIGNEDBYTE332,                     GLUNSIGNEDBYTE233REV,
       GLUNSIGNEDSHORT565, or GLUNSIGNEDSHORT565REV and  format  is
       not GLRGB.

       GLINVALIDOPERATION    is    generated    if    type    is    one   of
       GLUNSIGNEDSHORT4444,               GLUNSIGNEDSHORT4444REV,
       GLUNSIGNEDSHORT5551,               GLUNSIGNEDSHORT1555REV,
       GLUNSIGNEDINT8888,                   GLUNSIGNEDINT8888REV,
       GLUNSIGNEDINT1001001002,  or GLUNSIGNEDINT2100100100REV and for-
       mat is neither GLRGBA nor GLBGRA.

SEE ALSO
       glHistogram, glResetHistogram, glGetHistogramParameter



                                                            GLGETHISTOGRAM(3G)