glCopyColorTableSGI(3G)

NAME
     glCopyColorTableSGI - copy pixels into a color table


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


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

ASSOCIATED GETS
     glGetColorTableParameterSGI


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


SEE ALSO
     glColorTableSGI, glColorTableParameterSGI, glReadPixels.