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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 GL_COLOR_TABLE, GL_POST_CONVOLUTION_COLOR_TABLE, or
                       GL_POST_COLOR_MATRIX_COLOR_TABLE.

       internalformat  The internal storage  of the texture image.  Must be one of  the  following  symbolic
                       constants:  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, GL_RGBA16.

       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 GL_READ_BUFFER (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 asso-ciated associated
       ciated 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  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 components 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
        GL_ALPHA            A=Alpha
        GL_LUMINANCE        R=Luminance
        GL_LUMINANCE_ALPHA  A=Alpha, R=Luminance
        GL_INTENSITY        R=Intensity
        GL_RGB              R=Red, G=Green, B=Blue
        GL_RGBA             R=Red, G=Green, B=Blue, A=Alpha


       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
       glCopyColorTable is available only if GL_ARB_imaging is returned from  calling  glGetString  with  an
       argument of GL_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  is  generated  if  the  requested color table is too large to be supported by the
       implementation.

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

ASSOCIATED GETS
       glGetColorTable, glGetColorTableParameter

SEE ALSO
       glColorTable(3G), glColorTableParameter(3G), glReadPixels(3G)




                                                                                        GLCOPYCOLORTABLE(3G)