GLCOPYCOLORTABLE(3G)                                      GLCOPYCOLORTABLE(3G)



NAME
       glCopyColorTable - copy pixels into a color table


C SPECIFICATION
       void glCopyColorTable( GLenum target,
                              GLenum internalformat,
                              GLint x,
                              GLint y,
                              GLsizei width )


PARAMETERS
       target          The   color   table  target.  Must  be  GLCOLORTABLE,
                       GLPOSTCONVOLUTIONCOLORTABLE,                     or
                       GLPOSTCOLORMATRIXCOLORTABLE.

       internalformat  The  internal  storage   of the texture image.  Must be
                       one of  the  following  symbolic  constants:  GLALPHA,
                       GLALPHA4,     GLALPHA8,    GLALPHA12,    GLALPHA16,
                       GLUMINANCE,       GLUMINANCE4,       GLUMINANCE8,
                       GLUMINANCE12,   GLUMINANCE16,   GLUMINANCEALPHA,
                       GLUMINANCE4ALPHA4,             GLUMINANCE6ALPHA2,
                       GLUMINANCE8ALPHA8,            GLUMINANCE12ALPHA4,
                       GLUMINANCE12ALPHA12,         GLUMINANCE16ALPHA16,
                       GLINTENSITY,       GLINTENSITY4,       GLINTENSITY8,
                       GLINTENSITY12,  GLINTENSITY16,  GLR3G3B2,  GLRGB,
                       GLRGB4,    GLRGB5,   GLRGB8,   GLRGB100,   GLRGB12,
                       GLRGB16,  GLRGBA,  GLRGBA2,  GLRGBA4,   GLRGB5A1,
                       GLRGBA8, GLRGB100A2, GLRGBA12, GLRGBA16.

       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
       glCopyColorTable  loads  a  color  table  with  pixels from the current
       GLREADBUFER (rather than from  main  memory,  as  is  the  case  for
       glColorTable).

       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  unde-
       fined.

       The  pixels in the rectangle are processed just as if glReadPixels were
       called, with internalformat 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 compo-
       nents  of  each pixel. The scale and bias parameters are set by calling
       glColorTableParameter.

       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     Channel mapping
        GLALPHA            A=Alpha
        GLUMINANCE        R=Luminance
        GLUMINANCEALPHA  A=Alpha, R=Luminance
        GLINTENSITY        R=Intensity
        GLRGB              R=Red, G=Green, B=Blue
        GLRGBA             R=Red, G=Green, B=Blue, A=Alpha


       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].


NOTES
       glCopyColorTable  is  available only if GLARBimaging is returned from
       calling glGetString with an argument of GLEXTENSIONS.

ERORS
       GLINVALIDENUM is generated when target is not one  of  the  allowable
       values.

       GLINVALIDVALUE is generated if width is less than zero.

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

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

       GLINVALIDOPERATION  is  generated  if  glCopyColorTable  is  executed
       between the execution of glBegin and  the  corresponding  execution  of
       glEnd.

ASOCIATED GETS
       glGetColorTable, glGetColorTableParameter

SEE ALSO
       glColorTable, glColorTableParameter, glReadPixels



                                                          GLCOPYCOLORTABLE(3G)