GLGETCONVOLUTIONFILTER(3G)                          GLGETCONVOLUTIONFILTER(3G)



NAME
       glGetConvolutionFilter - get current 1D or 2D convolution filter kernel


C SPECIFICATION
       void glGetConvolutionFilter( GLenum target,
                                    GLenum format,
                                    GLenum type,
                                    GLvoid *image )


PARAMETERS
       target  The filter to be retrieved.  Must be one  of  GLCONVOLUTION1D
               or GLCONVOLUTION2D.

       format  Format  of  the output image.  Must be one of GLRED, GLGREN,
               GLBLUE,   GLALPHA,   GLRGB,   GLBGR,   GLRGBA,    GLBGRA,
               GLUMINANCE, or GLUMINANCEALPHA.

       type    Data  type  of  components  in the output image.  Symbolic con-
               stants GLUNSIGNEDBYTE, GLBYTE, GLBITMAP, GLUNSIGNEDSHORT,
               GLSHORT,        GLUNSIGNEDINT,       GLINT,       GLFLOAT,
               GLUNSIGNEDBYTE332,             GLUNSIGNEDBYTE233REV,
               GLUNSIGNEDSHORT565,           GLUNSIGNEDSHORT565REV,
               GLUNSIGNEDSHORT4444,       GLUNSIGNEDSHORT4444REV,
               GLUNSIGNEDSHORT5551,       GLUNSIGNEDSHORT1555REV,
               GLUNSIGNEDINT8888,           GLUNSIGNEDINT8888REV,
               GLUNSIGNEDINT1001001002,  and GLUNSIGNEDINT2100100100REV
               are accepted.

       image   Pointer to storage for the output image.

DESCRIPTION
       glGetConvolutionFilter returns the current 1D or 2D convolution  filter
       kernel  as  an  image.   The one- or two-dimensional image is placed in
       image according to the specifications in format  and  type.   No  pixel
       transfer operations are performed on this image, but the relevant pixel
       storage modes are applied.

       Color components that are present in format but  not  included  in  the
       internal   of  the  filter  are  returned  as zero.  The assignments of
       internal color components to the components of format are as follows.

        Internal Component          Resulting Component
        red                         red
        green                       green
        blue                        blue
        alpha                       alpha
        luminance                   red
        intensity                   red


NOTES
       glGetConvolutionFilter is present only if  GLARBimaging  is  returned
       when glGetString is called with an argument of GLEXTENSIONS.

       The    current   separable   2D   filter   must   be   retrieved   with
       glGetSeparableFilter rather than glGetConvolutionFilter.

ERORS
       GLINVALIDENUM is generated if target is not one of the allowable val-
       ues.

       GLINVALIDENUM is generated if format is not one of the allowable val-
       ues.

       GLINVALIDENUM is generated if type is not one of the  allowable  val-
       ues.

       GLINVALIDOPERATION is generated if glGetConvolutionFilter is executed
       between the execution of glBegin and  the  corresponding  execution  of
       glEnd.

       GLINVALIDOPERATION    is    generated    if    type    is    one   of
       GLUNSIGNEDBYTE332,                     GLUNSIGNEDBYTE233REV,
       GLUNSIGNEDSHORT565,  or  GLUNSIGNEDSHORT565REV and format is
       not GLRGB.

       GLINVALIDOPERATION   is    generated    if    type    is    one    of
       GLUNSIGNEDSHORT4444,               GLUNSIGNEDSHORT4444REV,
       GLUNSIGNEDSHORT5551,               GLUNSIGNEDSHORT1555REV,
       GLUNSIGNEDINT8888,                   GLUNSIGNEDINT8888REV,
       GLUNSIGNEDINT1001001002, or GLUNSIGNEDINT2100100100REV and  for-
       mat is neither GLRGBA nor GLBGRA.

ASOCIATED GETS
       glGetConvolutionParameter

SEE ALSO
       glGetSeparableFilter,   glConvolutionParameter,  glConvolutionFilter1D,
       glConvolutionFilter2D



                                                    GLGETCONVOLUTIONFILTER(3G)