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 convolution 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 generate 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 dimensions 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 kernel.

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, glConvolutionFilter2D, glSeparableFilter2D,
     glGetConvolutionParameter