glCopyColorTableSGI(3G)	       OpenGL Reference	       glCopyColorTableSGI(3G)

NAME    [Toc]    [Back]

     glCopyColorTableSGI - copy	pixels into a color table

C SPECIFICATION    [Toc]    [Back]

     void glCopyColorTableSGI( GLenum target,
			       GLenum internalformat,
			       GLint x,
			       GLint y,
			       GLsizei width )

PARAMETERS    [Toc]    [Back]

     target	     The color table target. Must be
		     GL_TEXTURE_COLOR_TABLE_SGI, GL_COLOR_TABLE_SGI,
		     GL_POST_CONVOLUTION_COLOR_TABLE_SGI, or
		     GL_POST_COLOR_MATRIX_COLOR_TABLE_SGI.

     internalformat  The internal storage format of the	texture	image.	Must
		     be	one of the following symbolic constants:  GL_ALPHA,
		     GL_ALPHA4_EXT, GL_ALPHA8_EXT, GL_ALPHA12_EXT,
		     GL_ALPHA16_EXT, GL_LUMINANCE, GL_LUMINANCE4_EXT,
		     GL_LUMINANCE8_EXT,	GL_LUMINANCE12_EXT,
		     GL_LUMINANCE16_EXT, GL_LUMINANCE_ALPHA,
		     GL_LUMINANCE4_ALPHA4_EXT, GL_LUMINANCE6_ALPHA2_EXT,
		     GL_LUMINANCE8_ALPHA8_EXT, GL_LUMINANCE12_ALPHA4_EXT,
		     GL_LUMINANCE12_ALPHA12_EXT, GL_LUMINANCE16_ALPHA16_EXT,
		     GL_INTENSITY_EXT, GL_INTENSITY4_EXT, GL_INTENSITY8_EXT,
		     GL_INTENSITY12_EXT, GL_INTENSITY16_EXT, GL_RGB,
		     GL_RGB2_EXT, GL_RGB4_EXT, GL_RGB5_EXT, GL_RGB8_EXT,
		     GL_RGB10_EXT, GL_RGB12_EXT, GL_RGB16_EXT, GL_RGBA,
		     GL_RGBA2_EXT, GL_RGBA4_EXT, GL_RGB5_A1_EXT, GL_RGBA8_EXT,
		     GL_RGB10_A2_EXT, GL_RGBA12_EXT, GL_RGBA16_EXT.

     x		     The x coordinate of the lower-left	corner of the pixel
		     rectangle to be transferred to the	color table.

     y		     The y coordinate of the lower-left	corner of the pixel
		     rectangle to be transferred to the	color table.

     width	     The width of the pixel rectangle.

DESCRIPTION    [Toc]    [Back]

     glCopyColorTableSGI loads a color table with pixels from the current
     GL_READ_BUFFER (rather than from main memory, as is the case for
     glColorTableSGI).

     The screen-aligned	pixel rectangle	with lower-left	corner at (x, y)
     having width width	and height 1 is	loaded into the	color table. If	any
     pixels within this	region are outside the window that is associated with
     the GL context, the values	obtained for those pixels are undefined.




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glCopyColorTableSGI(3G)	       OpenGL Reference	       glCopyColorTableSGI(3G)



     The pixels	in the rectangle are processed just as if glReadPixels were
     called, with format set to	RGBA, but processing stops after the final
     conversion	to RGBA.

     The four scale parameters and the four bias parameters that are defined
     for the table are then used to scale and bias the R, G, B,	and A
     components	of each	pixel.	( Use glTexParameter to	set the	scale and bias
     parameters	for the	texture	color table.  Use glColorTableParameterSGI, to
     set the scale and bias parameters for the other color tables.)

     Next, the R, G, B,	and A values are clamped to the	range [0,1].  Each
     pixel is then converted to	the internal format specified by
     internalformat. This conversion simply maps the component values of the
     pixel (R, G, B, and A) to the values included in the internal format
     (red, green, blue,	alpha, luminance, and intensity).  The mapping is as
     follows:

      Internal Format	   Red	 Green	 Blue	Alpha	Luminance   Intensity
      _______________________________________________________________________
      GL_ALPHA					  A
      GL_LUMINANCE					    R
      GL_LUMINANCE_ALPHA			  A	    R
      GL_INTENSITY_EXT							R
      GL_RGB		    R	   G	  B
      GL_RGBA		    R	   G	  B	  A

     Finally, the red, green, blue, alpha, luminance, and/or intensity
     components	of the resulting pixels	are stored in the color	table.	They
     form a one-dimensional table with indices in the range [0,	width -	1].

NOTES    [Toc]    [Back]

     glCopyColorTableSGI with target GL_COLOR_TABLE_SGI,
     GL_POST_CONVOLUTION_COLOR_TABLE_SGI, or
     GL_POST_COLOR_MATRIX_COLOR_TABLE_SGI is only available if both the
     EXT_copy_texture and the SGI_color_table extensions are supported.
     glCopyColorTableSGI with target GL_TEXTURE_COLOR_TABLE_SGI	is only
     available if both the EXT_copy_texture and	the SGI_texture_color_table
     extensions	are supported.	See glIntro for	more information about using
     extensions.

ERRORS    [Toc]    [Back]

     GL_INVALID_ENUM is	generated when target is not one of the	allowable
     values.

     GL_INVALID_VALUE is generated if width is less than zero.

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

     GL_TABLE_TOO_LARGE_EXT is generated if the	requested color	table is too
     large to be supported by the implementation.




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glCopyColorTableSGI(3G)	       OpenGL Reference	       glCopyColorTableSGI(3G)



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

ASSOCIATED GETS    [Toc]    [Back]

     glGetColorTableParameterSGI


MACHINE	DEPENDENCIES
     RealityEngine, RealityEngine2, and	VTX systems do not support
     glCopyColorTableSGI; calling it results in	a GL_INVALID_OPERATION error.

SEE ALSO    [Toc]    [Back]

     glColorTableSGI, glColorTableParameterSGI,	glReadPixels.


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