C SPECIFICATION

       void GLAPIENTRY glCopyConvolutionFilter2D( GLenum targe )

PARAMETERS

       targe  Must be GL_CONVOLUTION_2D.

       _param2
              The internal format  of  the  convolution  filter  kernel.   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, or GL_RGBA16.

       _param3, _param4
              The window space coordinates of the lower-left coordinate of the
              pixel array to copy.

       _param5
              The width of the pixel array to copy.

       _param6
              The height of the pixel array to copy.

DESCRIPTION

       glCopyConvolutionFilter2D  defines a two-dimensional convolution filter
       kernel with pixels from the current GL_READ_BUFFER  (rather  than  from
       main memory, as is the case for glConvolutionFilter2D).

       The   screen-aligned   pixel   rectangle   with  lower-left  corner  at
       (_param3, _param4), width _param5 and height _param6 is used to  define
       the  convolution  filter.  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 exactly as if glReadPixels
       had been called with format set to RGBA, but  the  process  stops  just
       before  final  conversion.  The R, G, B, and A components of each pixel
       are next scaled by the four 2D  GL_CONVOLUTION_FILTER_SCALE  parameters
       and  biased by the four 2D GL_CONVOLUTION_FILTER_BIAS parameters.  (The
       scale and bias parameters are set by glConvolutionParameter  using  the
       GL_CONVOLUTION_2D  target and the names GL_CONVOLUTION_FILTER_SCALE and
       GL_CONVOLUTION_FILTER_BIAS.  The parameters themselves are  vectors  of
       four  values  that  are applied to red, green, blue, and alpha, in that
       GL_LUMINANCE                                R
       GL_LUMINANCE_ALPHA                  A       R
       GL_INTENSITY                                                      R
       GL_RGB                R      G      B
       GL_RGBA               R      G      B       A
       ------------------------------------------------------------------------

       The  red, green, blue, alpha, luminance, and/or intensity components of
       the resulting pixels are stored in floating-point rather  than  integer
       format.

       Pixel  ordering  is  such that lower x screen coordinates correspond to
       lower i filter image coordinates, and lower y screen coordinates corre-
       spond to lower j filter image coordinates.

       Note  that after a convolution is performed, the resulting color compo-
       nents     are     also     scaled      by      their      corresponding
       GL_POST_CONVOLUTION_c_SCALE  parameters and biased by their correspond-
       ing GL_POST_CONVOLUTION_c_BIAS parameters (where c takes on the  values
       RED,   GREEN,   BLUE,   and   ALPHA).   These  parameters  are  set  by
       glPixelTransfer.

NOTES

       glCopyConvolutionFilter2D is present only if GL_ARB_imaging is returned
       when glGetString is called with an argument of GL_EXTENSIONS.

ERRORS

       GL_INVALID_ENUM is generated if targe is not GL_CONVOLUTION_2D.

       GL_INVALID_ENUM  is  generated  if  _param2 is not one of the allowable
       values.

       GL_INVALID_VALUE is generated if _param5 is less than zero  or  greater
       than  the  maximum  supported  value.   This  value may be queried with
       glGetConvolutionParameter  using  target  GL_CONVOLUTION_2D  and   name
       GL_MAX_CONVOLUTION_WIDTH.

       GL_INVALID_VALUE  is  generated if _param6 is less than zero or greater
       than the maximum supported value.   This  value  may  be  queried  with
       glGetConvolutionParameter   using  target  GL_CONVOLUTION_2D  and  name
       GL_MAX_CONVOLUTION_HEIGHT.

       GL_INVALID_OPERATION is generated if glCopyConvolutionFilter2D is  exe-
       cuted  between the execution of glBegin and the corresponding execution
       of glEnd.

ASSOCIATED GETS

       glGetConvolutionParameter, glGetConvolutionFilter

SEE ALSO

       glConvolutionFilter2D, glConvolutionParameter, glPixelTransfer