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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	speci‐
		       fied 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 compo‐
       nents 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 converted to the internal  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  (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  com‐
       ponents	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 target of GL_PROXY_*.  This allows the
       application to decide if a particular glColorTable command  would  suc‐
       ceed,  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  con‐
       tents 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 modified 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 val‐
       ues.

       GL_INVALID_ENUM is generated if internalformat is not one of the allow‐
       able 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 val‐
       ues.

       GL_INVALID_ENUM	is  generated if type is not one of the allowable val‐
       ues.

       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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