glMinmax(3G)		       OpenGL Reference			  glMinmax(3G)

NAME    [Toc]    [Back]

     glMinmax -	define minmax table

C SPECIFICATION    [Toc]    [Back]

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

PARAMETERS    [Toc]    [Back]

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

     internalformat  The format	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 process
		     and no drawing or texture loading will take place.	 If
		     GL_FALSE, pixels will proceed to the final	conversion
		     process after minmax.

DESCRIPTION    [Toc]    [Back]

     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 format of the minmax table
     includes luminance, then the R color component of incoming	pixels is used
     for comparison.)  The contents of the minmax table	may be retrieved at a
     later time	by calling glGetMinmax.	 The minmax operation is enabled or
     disabled by calling glEnable or glDisable,	respectively, with an argument
     of	GL_MINMAX.

     glMinmax redefines	the current minmax table to have entries of the	format
     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



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glMinmax(3G)		       OpenGL Reference			  glMinmax(3G)



     pixels are	discarded after	minmax;	no further processing of the pixels
     takes place, and no drawing, texture loading, or pixel readback will
     result.

NOTES    [Toc]    [Back]

     glMinmax is present only if GL_ARB_imaging	is returned when glGetString
     is	called with an argument	of GL_EXTENSIONS.

ERRORS    [Toc]    [Back]

     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    [Toc]    [Back]

     glGetMinmaxParameter

SEE ALSO    [Toc]    [Back]

     glGetMinmax, glResetMinmax


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