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GLCONVOLUTIONPARAMETER(3G)                                                        GLCONVOLUTIONPARAMETER(3G)



NAME
       glConvolutionParameterf,  glConvolutionParameteri, glConvolutionParameterfv, glConvolutionParameteriv
       - set convolution parameters


C SPECIFICATION
       void glConvolutionParameterf( GLenum target,
                                     GLenum pname,
                                     GLfloat params )
       void glConvolutionParameteri( GLenum target,
                                     GLenum pname,
                                     GLint params )

PARAMETERS
       target  The  target  for  the   convolution   parameter.    Must   be   one   of   GL_CONVOLUTION_1D,
               GL_CONVOLUTION_2D, or GL_SEPARABLE_2D.

       pname   The parameter to be set.  Must be GL_CONVOLUTION_BORDER_MODE.

       params  The parameter value.  Must be one of GL_REDUCE, GL_CONSTANT_BORDER, GL_REPLICATE_BORDER.



C SPECIFICATION
       void glConvolutionParameterfv( GLenum target,
                                      GLenum pname,
                                      const GLfloat *params )
       void glConvolutionParameteriv( GLenum target,
                                      GLenum pname,
                                      const GLint *params )

PARAMETERS
       target The   target   for   the   convolution   parameter.    Must   be   one  of  GL_CONVOLUTION_1D,
              GL_CONVOLUTION_2D, or GL_SEPARABLE_2D.

       pname  The   parameter    to    be    set.     Must    be    one    of    GL_CONVOLUTION_BORDER_MODE,
              GL_CONVOLUTION_BORDER_COLOR, GL_CONVOLUTION_FILTER_SCALE, or GL_CONVOLUTION_FILTER_BIAS.

       params The parameter value.  If pname is GL_CONVOLUTION_BORDER_MODE, params must be one of GL_REDUCE,
              GL_CONSTANT_BORDER, or GL_REPLICATE_BORDER.  Otherwise, must be a vector of four  values  (for
              red,   green,  blue,  and  alpha,  respectively)  to  be  used  for  scaling  (when  pname  is
              GL_CONVOLUTION_FILTER_SCALE), or biasing (when pname is GL_CONVOLUTION_FILTER_BIAS) a convolu-tion convolution
              tion    filter    kernel   or   setting   the   constant   border   color   (when   pname   is
              GL_CONVOLUTION_BORDER_COLOR.

DESCRIPTION
       glConvolutionParameter sets the value of a convolution parameter.

       target selects the convolution  filter  to  be  affected:  GL_CONVOLUTION_1D,  GL_CONVOLUTION_2D,  or
       GL_SEPARABLE_2D for the 1D, 2D, or separable 2D filter, respectively.

       pname     selects     the    parameter    to    be    changed.     GL_CONVOLUTION_FILTER_SCALE    and
       GL_CONVOLUTION_FILTER_BIAS  affect  the  definition   of   the   convolution   filter   kernel;   see
       glConvolutionFilter1D,  glConvolutionFilter2D,  and glSeparableFilter2D for details.  In these cases,
       params is an array of four values to be applied to red, green, blue, and alpha values,  respectively.
       The  initial  value  for  GL_CONVOLUTION_FILTER_SCALE  is  (1,  1,  1,  1), and the initial value for
       GL_CONVOLUTION_FILTER_BIAS is (0, 0, 0, 0).

       A pname value of GL_CONVOLUTION_BORDER_MODE controls the convolution border mode. The accepted  modes
       are:

       GL_REDUCE
              The image resulting from convolution is smaller than the source image.  If the filter width is
              Wf and height is Hf, and the source image width is Ws and height is  Hs,  then  the  convolved
              image width will be Ws - Wf + 1 and height will be Hs - Hf + 1.  (If this reduction would gen-erate generate
              erate an image with zero or negative width and/or height, the output is simply null,  with  no
              error generated.)  The coordinates of the image resulting from convolution are zero through Ws
              - Wf in width and zero through Hs - Hf in height.

       GL_CONSTANT_BORDER
              The image resulting from convolution is the same size as the source image, and processed as if
              the   source   image   were   surrounded   by   pixels  with  their  color  specified  by  the
              GL_CONVOLUTION_BORDER_COLOR.

       GL_REPLICATE_BORDER
              The image resulting from convolution is the same size as the source image, and processed as if
              the outermost pixel on the border of the source image were replicated.

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

       In cases where errors can result from the specification of invalid image dimensions, it is the dimen-sions dimensions
       sions  after  convolution  that  are  tested,  not  the dimensions of the source image.  For example,
       glTexImage1D requires power-of-two image size.  When GL_REDUCE border mode is in effect,  the  source
       image must be larger than the final power-of-two size by one less than the size of the 1D filter ker-nel. kernel.
       nel.

ERRORS
       GL_INVALID_ENUM is generated if target is not one of the allowable values.

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

       GL_INVALID_ENUM is generated if  pname  is  GL_CONVOLUTION_BORDER_MODE  and  params  is  not  one  of
       GL_REDUCE, GL_CONSTANT_BORDER, or GL_REPLICATE_BORDER.

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

ASSOCIATED GETS
       glGetConvolutionParameter

SEE ALSO
       glConvolutionFilter1D(3G), glConvolutionFilter2D(3G), glSeparableFilter2D(3G), glGetConvolutionParameter(3G)




                                                                                  GLCONVOLUTIONPARAMETER(3G)