glConvolutionParameter

GLCONVOLUTIONPARAMETER(3G)			   GLCONVOLUTIONPARAMETER(3G)



NAME
       glConvolutionParameterf, glConvolutionParameteri, glConvolutionParame-
       terfv, 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	 val-
	      ues  (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 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 convo-
	      lution 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	 sur-
	      rounded	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 val-
       ues.

       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	 exe-
       cuted 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)