glResetHistogramEXT man page on Solaris

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GLHISTOGRAMEXT(3GL)					   GLHISTOGRAMEXT(3GL)

NAME
       glHistogramEXT,	glResetHistogramEXT - specify histogram parameters and
       reset internal representation of histogram

C SPECIFICATION
       void glHistogramEXT ( GLenum target,
	      GLsizei width,
	      GLenum internalformat,
	      GLboolean sink)

PARAMETERS
       target	       The target histogram to be  defined.  Must  be  GL_HIS‐
		       TOGRAM_EXT or GL_PROXY_HISTOGRAM_EXT.

       width	       Width  of  the histogram. Represents the number of bins
		       in which the histogram is stored.   internalformat  The
		       internal	 storage format of the histogram.  sink Speci‐
		       fies whether pixel groups will be consumed by the  his‐
		       togram  operation  (GL_TRUE) or passed on to the minmax
		       operation (GL_FALSE).

C SPECIFICATION
       void glResetHistogramEXT ( GLenum target)

PARAMETERS
       target	The target histogram to be reset. Must be GL_HISTOGRAM_EXT.

DESCRIPTION
       glHistogramEXT and glResetHistogramEXT are part	of  the	 EXT_histogram
       extension,  which  defines  histogram  and minmax operations at a fixed
       location in the pixel transfer pipeline after convolution and post con‐
       volution colortable.

       glResetHistogramEXT resets the internal representation of the histogram
       to all zeros.

       Histogram is Enabled glEnable(GL_HISTOGRAM_EXT). Use  glDisable(GL_HIS‐
       TOGRAM_EXT) to disable histogram.  Use glIsEnabled(GL_HISTOGRAM_EXT) to
       check if histogram is enabled or not.

       The width of the histogram must be a power of 2. The maximum width of a
       histogram  is 65536. If the histogram width is less than zero or is not
       a power of 2 then an error  is  generated  (GL_INVALID_VALUE).  If  the
       width  is  larger  than	the  maximum allowed histogram width, then the
       error GL_TABLE_TOO_LARGE_EXT is generated.

       The error INVALID_ENUM results if <internalformat> is not  one  of  the
       values accepted by the <components> parameter of TexImage2D (as defined
       by EXT_texture), except that values 1, 2, 3, 4,	INTENSITY_EXT,	INTEN‐
       SITY4_EXT, INTENSITY8_EXT, INTENSITY12_EXT, and INTENSITY16_EXT are not
       accepted.

       If no error results from the execution of HistogramEXT,	the  specified
       histogram  table	 is  redefined	to have <width> entries, each with the
       specified internal format. The entries are indexed  zero	 through  N-1,
       where N is the <width> of the table. Each value in each entry is set to
       zero. The values in the previous histogram table, if any, are lost.

       Histogram operations are performed only for RGBA pixel  groups,	though
       these  groups may have been specified as color indices and converted to
       RGBA by index table lookup. If  GL_HISTOGRAM_EXT	 is  enabled  and  the
       width  of the table is non-zero, and the pixel groups contain RGBA val‐
       ues, then indices Ri, Gi, Bi, and Ai are derived from the  red,	green,
       blue, and alpha components of each pixel group (without modifying these
       components) by clamping the components to [0,1],	 multiplying  each  by
       one  less  than	the width of the histogram table, and rounding each to
       the nearest integer.  If	 the  format  of  the  GL_HISTOGRAM_EXT	 table
       includes	 red or luminance, the red or luminance component of histogram
       entry Ri is incremented by one. If the format of	 the  GL_HISTOGRAM_EXT
       table  includes	green,	the  green  component of histogram entry Gi is
       incremented by one. The blue and alpha components of histogram  entries
       Bi  and Ai are incremented in the same way. If a histogram entry compo‐
       nent is incremented beyond its maximum value, its value	becomes	 unde‐
       fined. (This is not an error.)

       By  default  histogram  operation  has no effect on the stream of pixel
       groups being processed.	However, if GL_HISTOGRAM_EXT  is  enabled  and
       the  histogram  <sink> parameter was specified as GL_TRUE then all RGBA
       pixel groups are discarded immediately after the histogram operation is
       completed.  Because histogram precedes minmax, no minmax operation will
       be performed. No pixel fragments are generated, no change  is  made  to
       texture memory contents, and no pixel values are returned.

       The  operation  of  histogram during pixel copy and query operations is
       identical to the operation during pixel drawing and texture image defi‐
       nition.

NOTES
       glHistogramEXT  with a GL_PROXY_HISTOGRAM_EXT target is not included in
       display lists. It is executed immediately when called.

ERRORS
       GL_INVALID_ENUM is generated if glHistogramEXT  parameter  <target>  is
       not GL_HISTOGRAM_EXT or GL_PROXY_HISTOGRAM_EXT.

       GL_INVALID_VALUE	 is  generated	if glHistogramEXT parameter <width> is
       less than zero or is not a power of 2.

       GL_INVALID_ENUM is generated if glHistogramEXT parameter	 <internalfor‐
       mat>   is   not	 GL_ALPHA,  GL_RGB,  GL_RGBA,  GL_LUMINANCE,  GL_LUMI‐
       NANCE_ALPHA, or one of the tokens defined by the EXT_texture extension.
       (Values	1,  2,	3,  4,	INTENSITY_EXT, INTENSITY4_EXT, INTENSITY8_EXT,
       INTENSITY12_EXT, and INTENSITY16_EXT are not accepted as internal  for‐
       mats by glHistogramEXT).

       GL_TABLE_TOO_LARGE_EXT  is  generated  if glHistogramEXT is called with
       parameter <target> of GL_HISTOGRAM_EXT and the histogram	 as  specified
       is too large for the implementation.

       GL_INVALID_ENUM	is generated if glResetHistogramEXT parameter <target>
       is not GL_HISTOGRAM_EXT.

       GL_INVALID_OPERATION is	generated  if  glHistogramEXT  or  glResetHis‐
       togramEXT  is called between execution of glBegin and the corresponding
       execution of glEnd.

ASSOCIATED GETS
       glGetHistogramEXT, glGetHistogramParameterivEXT,	 glGetHistogramParame‐
       terfvEXT

SEE ALSO
       glMinmaxEXT,   glResetMinmaxEXT,	  glGetMinmaxEXT,   glGetMinmaxParame‐
       terivEXT,   glGetMinmaxParameterfvEXT,	glDrawPixels,	 glCopyPixels,
       glReadPixels,	glTexImage2D,	glTexImage3DEXT,   glTexSubImage2DEXT,
       glCopyTexImage2DEXT,  glCopyTexSubImage2DEXT,  glGetTexImage,  glPixel‐
       Tranferf,  glPixelTransferi, glEnable, glDisable, glIsEnabled, glPixel‐
       Store.

				   1 Dec 97		   GLHISTOGRAMEXT(3GL)
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