glMinmax

GLMINMAX(3G)							 GLMINMAX(3G)



NAME
       glMinmax - define minmax table


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


PARAMETERS
       target	       The minmax table whose parameters are to be set.	 Must
		       be GL_MINMAX.

       internalformat  The  of entries in the minmax table.  Must be  one  of
		       GL_ALPHA,     GL_ALPHA4,	    GL_ALPHA8,	  GL_ALPHA12,
		       GL_ALPHA16,	  GL_LUMINANCE,	       GL_LUMINANCE4,
		       GL_LUMINANCE8,	  GL_LUMINANCE12,     GL_LUMINANCE16,
		       GL_LUMINANCE_ALPHA,		GL_LUMINANCE4_ALPHA4,
		       GL_LUMINANCE6_ALPHA2,		GL_LUMINANCE8_ALPHA8,
		       GL_LUMINANCE12_ALPHA4,	      GL_LUMINANCE12_ALPHA12,
		       GL_LUMINANCE16_ALPHA16,	GL_R3_G3_B2, GL_RGB, GL_RGB4,
		       GL_RGB5,	 GL_RGB8,   GL_RGB10,	GL_RGB12,   GL_RGB16,
		       GL_RGBA,	 GL_RGBA2,  GL_RGBA4,  GL_RGB5_A1,  GL_RGBA8,
		       GL_RGB10_A2, GL_RGBA12, or GL_RGBA16.

       sink	       If GL_TRUE, pixels will be consumed by the minmax pro-
		       cess  and  no  drawing  or  texture  loading will take
		       place.  If GL_FALSE, pixels will proceed to the	final
		       conversion process after minmax.

DESCRIPTION
       When  GL_MINMAX is enabled, the RGBA components of incoming pixels are
       compared to the minimum and maximum values for each  component,	which
       are  stored  in the 2-element minmax table.  (The first element stores
       the minima, and the second element stores the  maxima.)	 If  a	pixel
       component  is  greater than the corresponding component in the maximum
       element, then the maximum element is updated with the pixel  component
       value.	If a pixel component is less than the corresponding component
       in the minimum element, then the minimum element is updated  with  the
       pixel component value.  (In both cases, if the internal	of the minmax
       table includes luminance, then the R color component of incoming	 pix-
       els  is used for comparison.)  The contents of the minmax table may be
       retrieved at a later time by calling glGetMinmax.  The  minmax  opera-
       tion  is enabled or disabled by calling glEnable or glDisable, respec-
       tively, with an argument of GL_MINMAX.

       glMinmax redefines the current minmax table to  have  entries  of  the
       specified  by internalformat.  The maximum element is initialized with
       the smallest possible component values, and  the	 minimum  element  is
       initialized with the largest possible component values.	The values in
       the previous minmax table, if any, are lost.  If sink is GL_TRUE, then
       pixels are discarded after minmax; no further processing of the pixels
       takes place, and no drawing, texture loading, or pixel  readback	 will
       result.


NOTES
       glMinmax	  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  one  of  the  allowable
       values.

       GL_INVALID_ENUM	is  generated  if  internalformat  is  not one of the
       allowable values.

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

ASSOCIATED GETS
       glGetMinmaxParameter

SEE ALSO
       glGetMinmax(3G), glResetMinmax(3G)



								 GLMINMAX(3G)