glMinmaxEXT man page on SunOS

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GLMINMAXEXT(3GL)					      GLMINMAXEXT(3GL)

NAME
       glMinmaxEXT,  glResetMinmaxEXT  -  specify  minmax parameters and reset
       internal representation of minmax

C SPECIFICATION
       void glMinmaxEXT ( GLenum target,
	      GLenum internalformat,
	      GLboolean sink)

PARAMETERS
       target	       The target minax to be defined.	Must be	 GL_MINMAX_EXT
		       or GL_PROXY_HISTOGRAM_EXT.

       internalformat  The internal storage format of minmax values.

       sink	       Specifies  whether pixel groups will be consumed by the
		       minmax operation (GL_TRUE) or passed on to  pixel  ras‐
		       torization (GL_FALSE).

C SPECIFICATION
       void glResetMinmaxEXT ( GLenum target)

PARAMETERS
       target	The target minmax to be reset.	Must be GL_MINMAX_EXT.

DESCRIPTION
       glMinmaxEXT  and	 glResetMinmaxEXT are part of the EXT_histogram exten‐
       sion, which defines histogram and minmax operations at a fixed location
       in  the	pixel transfer pipeline after convolution and post convolution
       colortable.

       The minmax operation immediately follows the histogram  operation,  but
       will  only  be executed if both the histogram and minmax operations are
       enabled. Also, if the sink value for histogram is set to GL_TRUE,  then
       the minmax operation will not be executed.

       A  minmax  table is specified using the glMinmaxEXT command.  Its <tar‐
       get> parameter must be GL_MINMAX_EXT. <internalformat> may  be  any  of
       the  token  values  accepted  by the <components> parameter of glTexIm‐
       age2D, except that 1, 2,	 3,  4,	 GL_INTENSITY_EXT,  GL_INTENSITY4_EXT,
       GL_INTENSITY8_EXT,  GL_INTENSITY12_EXT,	and GL_INTENSITY16_EXT are not
       accepted.  <sink> is set to GL_TRUE or GL_FALSE. The  resulting	minmax
       table  always has 2 entries, each with values corresponding only to the
       components of the internal format.

       glResetMinmaxEXT resets the internal representation of  minmax  to  all
       zeros.

       Minmax is Enabled glEnable(GL_MINMAX_EXT). Use glDisable(GL_MINMAX_EXT)
       to disable minmax. Use glIsEnabled(GL_MINMAX_EXT) to check if minmax is
       enabled or not.

       Minmax  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_MINMAX_EXT is enabled, and the pixel groups contain RGBA values,
       then the red, green, blue, and alpha components of each group are  com‐
       pared  to  the minimum and maximum values for each, which are stored in
       the 2-element minmax table. (The first element stores the minimum  val‐
       ues,  the second stores the maximum values.)  If the format of this ta‐
       ble includes red or luminance, the red component value replaces the red
       or  luminance  value  in the minimum table element if and only if it is
       less than that component. Likewise, if the format includes red or lumi‐
       nance  and  the	red  component of the group is greater than the red or
       luminance value	in  the	 maximum  element,  the	 red  group  component
       replaces the red or luminance maximum component.

       If  the	format	of the table includes green, the green group component
       conditionally replaces the  green  minimum  and/or  maximum  if	it  is
       smaller	or  larger,  respectively. The blue and alpha group components
       are similarly tested and replaced, if the table	format	includes  blue
       and/or  alpha.  The  internal type of the minimum and maximum component
       values is floating point. There are no semantics defined for the treat‐
       ment of group component values that are outside the representable range
       of the minimum and maximum values.

       By default histogram and minmax operations have no effect on the stream
       of pixel groups being processed. If GL_HISTOGRAM_EXT is enabled and the
       histogram <sink> parameter was specified as GL_TRUE, however, all  RGBA
       pixel groups are discarded immediately after the histogram operation is
       completed. Because histogram precedes minmax, no	 minmax	 operation  is
       performed.  No pixel fragments are generated, no change is made to tex‐
       ture memory contents, and no pixel  values  are	returned.  If  GL_MIN‐
       MAX_EXT	is  enabled  and  the minmax <sink> parameter was specified as
       GL_TRUE, all RGBA pixel groups are discarded immediately after the min‐
       max  operation  is  completed. Because minmax follows histogram, a his‐
       togram operation with <sink> set to GL_FALSE may precede such a	minmax
       operation. Again no pixel fragments are generated, no change is made to
       texture memory contents, and no pixel values are returned.

       The operation of minmax during pixel copy and query operations is iden‐
       tical  to  the operation during pixel drawing and texture image defini‐
       tion.

ERRORS
       GL_INVALID_ENUM is generated if glMinmaxEXT parameter <target>  is  not
       GL_MINMAX_EXT.

       GL_INVALID_ENUM	is generated if glMinmaxEXT parameter <internalformat>
       is not GL_RED, GL_GREEN, GL_BLUE, GL_ALPHA, GL_RGB,  GL_RGBA,  GL_LUMI‐
       NANCE, GL_LUMINANCE_ALPHA and GL_ABGR_EXT, or one of the tokens defined
       by the EXT_texture extension. (Values 1,	 2,  3,	 4,  GL_INTENSITY_EXT,
       GL_INTENSITY4_EXT, GL_INTENSITY8_EXT, GL_INTENSITY12_EXT, and GL_INTEN‐
       SITY16_EXT are not accepted as internal formats by glMinmaxEXT).

       GL_INVALID_ENUM is generated if glResetMinmaxEXT parameter <target>  is
       not GL_MINMAX_EXT.

       GL_INVALID_OPERATION  is	 generated if MinmaxEXT and ResetMinmaxEXT are
       called between execution of glBegin and the corresponding execution  of
       glEnd.

ASSOCIATED GETS
       glGetMinmaxEXT,	glGetMinmaxParameterivEXT,  and	 glGetMinmaxParameter‐
       fvEXT

SEE ALSO
       glHistogramEXT, glResetHistogramEXT, glGetHistogramEXT, glGetHistogram‐
       ParameterivEXT,	glGetHistogramParameterfvEXT, glDrawPixels, glCopyPix‐
       els, glReadPixels, glTexImage2D,	 glTexImage3DEXT,  glTexSubImage2DEXT,
       glCopyTexImage2DEXT,  glCopyTexSubImage2DEXT,  glGetTexImage,  glPixel‐
       Tranferf, glPixelTransferi, glEnable, glDisable, glIsEnabled,  glPixel‐
       Store.

				   1 Dec 97		      GLMINMAXEXT(3GL)
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