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GLCOLORTABLE(3G)								 GLCOLORTABLE(3G)

NAME
       glColorTable - define a color lookup table

C SPECIFICATION
       void glColorTable( GLenum target,
			  GLenum internalformat,
			  GLsizei width,
			  GLenum format,
			  GLenum type,
			  const GLvoid *table )

PARAMETERS
       target	       Must    be   one   of   GL_COLOR_TABLE,	 GL_POST_CONVOLUTION_COLOR_TABLE,
		       GL_POST_COLOR_MATRIX_COLOR_TABLE,		    GL_PROXY_COLOR_TABLE,
		       GL_PROXY_POST_CONVOLUTION_COLOR_TABLE,				       or
		       GL_PROXY_POST_COLOR_MATRIX_COLOR_TABLE.

       internalformat  The internal  of the color table.   The	allowable  values  are	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_INTENSITY,	  GL_INTENSITY4,      GL_INTENSITY8,	  GL_INTENSITY12,
		       GL_INTENSITY16, 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, and GL_RGBA16.

       width	       The number of entries in the color lookup table specified by table.

       format	       The  of the pixel  data	in  table.   The  allowable  values  are  GL_RED,
		       GL_GREEN,  GL_BLUE,  GL_ALPHA,  GL_LUMINANCE,  GL_LUMINANCE_ALPHA, GL_RGB,
		       GL_BGR, GL_RGBA, and GL_BGRA.

       type	       The  type  of  the  pixel  data	in  table.   The  allowable  values   are
		       GL_UNSIGNED_BYTE,  GL_BYTE,  GL_UNSIGNED_SHORT, GL_SHORT, GL_UNSIGNED_INT,
		       GL_INT,	GL_FLOAT,   GL_UNSIGNED_BYTE_3_3_2,   GL_UNSIGNED_BYTE_2_3_3_REV,
		       GL_UNSIGNED_SHORT_5_6_5, 		     GL_UNSIGNED_SHORT_5_6_5_REV,
		       GL_UNSIGNED_SHORT_4_4_4_4,		   GL_UNSIGNED_SHORT_4_4_4_4_REV,
		       GL_UNSIGNED_SHORT_5_5_5_1,		   GL_UNSIGNED_SHORT_1_5_5_5_REV,
		       GL_UNSIGNED_INT_8_8_8_8, 		     GL_UNSIGNED_INT_8_8_8_8_REV,
		       GL_UNSIGNED_INT_10_10_10_2, and GL_UNSIGNED_INT_2_10_10_10_REV.

       table	       Pointer	to  a  one-dimensional	array  of pixel data that is processed to
		       build the color table.

DESCRIPTION
       glColorTable may be used in two ways: to test the actual size and color	resolution  of	a
       lookup  table  given  a	particular  set of parameters, or to load the contents of a color
       lookup table.  Use the targets GL_PROXY_* for the first case and the other targets for the
       second case.

       If	target	    is	    GL_COLOR_TABLE,	 GL_POST_CONVOLUTION_COLOR_TABLE,      or
       GL_POST_COLOR_MATRIX_COLOR_TABLE, glColorTable builds a color lookup table from	an  array
       of  pixels.  The pixel array specified by width, format, type, and table is extracted from
       memory and processed just as if glDrawPixels were called, but processing stops  after  the
       final expansion to RGBA is completed.

       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
       glColorTableParameter to set these scale and bias parameters.)

       Next,  the R, G, B, and A values are clamped to the range [0, 1].  Each pixel is then con-
       verted to the internal  specified by internalformat.  This conversion simply maps the com-
       ponent  values of the pixel (R, G, B, and A) to the values included in the internal  (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							  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].

       If target is GL_PROXY_*, glColorTable recomputes and stores the values of the proxy  color
       table's	     state	 variables	GL_COLOR_TABLE_FORMAT,	    GL_COLOR_TABLE_WIDTH,
       GL_COLOR_TABLE_RED_SIZE,       GL_COLOR_TABLE_GREEN_SIZE,	GL_COLOR_TABLE_BLUE_SIZE,
       GL_COLOR_TABLE_ALPHA_SIZE,		 GL_COLOR_TABLE_LUMINANCE_SIZE, 	      and
       GL_COLOR_TABLE_INTENSITY_SIZE.  There is no effect on the image or  state  of  any  actual
       color  table.   If  the	specified  color table is too large to be supported, then all the
       proxy state variables listed above are set to zero.  Otherwise, the color table	could  be
       supported  by  glColorTable  using the corresponding non-proxy target, and the proxy state
       variables are set as if that target were being defined.

       The proxy state variables can be retrieved by calling glGetColorTableParameter with a tar-
       get  of	GL_PROXY_*.   This  allows the application to decide if a particular glColorTable
       command would succeed, and to determine what the resulting color  table	attributes  would
       be.

       If  a  color  table  is	enabled, and its width is non-zero, then its contents are used to
       replace a subset of the components of each RGBA pixel group, based on the internal  of the
       table.

       Each  pixel group has color components (R, G, B, A) that are in the range [0.0, 1.0].  The
       color components are rescaled to the size of the color lookup  table  to  form  an  index.
       Then  a	subset	of the components based on the internal  of the table are replaced by the
       table entry selected by that index.  If the color components and contents of the table are
       represented as follows:

			   --------------------------------------------------
			   Representation		Meaning
			   --------------------------------------------------
				 r	    Table index computed from R
				 g	    Table index computed from G
				 b	    Table index computed from B
				 a	    Table index computed from A
				L[i]	    Luminance value at table index i
				I[i]	    Intensity value at table index i
				R[i]	    Red value at table index i
				G[i]	    Green value at table index i
				B[i]	    Blue value at table index i
				A[i]	    Alpha value at table index i
			   --------------------------------------------------

       then the result of color table lookup is as follows:

			  -----------------------------------------------------
						  Resulting Texture Components
			  Table Internal Format   R	  G	 B	 A
			  -----------------------------------------------------
			  GL_ALPHA		  R	  G	 B	 A[a]
			  GL_LUMINANCE		  L[r]	  L[g]	 L[b]	 At
			  GL_LUMINANCE_ALPHA	  L[r]	  L[g]	 L[b]	 A[a]
			  GL_INTENSITY		  I[r]	  I[g]	 I[b]	 I[a]
			  GL_RGB		  R[r]	  G[g]	 B[b]	 A

			  GL_RGBA		  R[r]	  G[g]	 B[b]	 A[a]
			  -----------------------------------------------------

       When  GL_COLOR_TABLE  is enabled, the colors resulting from the pixel map operation (if it
       is enabled) are mapped by the color lookup table before being passed  to  the  convolution
       operation.  The	colors	resulting from the convolution operation are modified by the post
       convolution color lookup table when GL_POST_CONVOLUTION_COLOR_TABLE is enabled. These mod-
       ified   colors	are   then   sent   to	 the   color   matrix	operation.   Finally,  if
       GL_POST_COLOR_MATRIX_COLOR_TABLE is enabled, the colors resulting from  the  color  matrix
       operation  are mapped by the post color matrix color lookup table before being used by the
       histogram operation.

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

       If    target    is    set    to	  GL_COLOR_TABLE,   GL_POST_CONVOLUTION_COLOR_TABLE,   or
       GL_POST_COLOR_MATRIX_COLOR_TABLE, then width must be a power of two or a  GL_INVALID_VALUE
       error is generated.

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_VALUE is generated if width is less than zero.

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

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

       GL_TABLE_TOO_LARGE  is generated if the requested color table is too large to be supported
       by the implementation, and target is not a GL_PROXY_* target.

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

ASSOCIATED GETS
       glGetColorTableParameter

SEE ALSO
       glColorSubTable(3G),	       glColorTableParameter(3G),	    glCopyColorTable(3G),
       glCopyColorSubTable(3G), glGetColorTable(3G)

										 GLCOLORTABLE(3G)
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