glGetHistogram(3)

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   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 con-
               stants 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 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  GL_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 val-
       ues.

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

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

       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 for-
       mat is neither GL_RGBA nor GL_BGRA.

SEE ALSO

       glHistogram(3G), glResetHistogram(3G), glGetHistogramParameter(3G)

                                                            GLGETHISTOGRAM(3G)