glGetConvolutionFilter(3)

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  GL_CONVOLUTION_1D
               or GL_CONVOLUTION_2D.

       format  Format  of  the output image.  Must be one of GL_RED, GL_GREEN,
               GL_BLUE,   GL_ALPHA,   GL_RGB,   GL_BGR,   GL_RGBA,    GL_BGRA,
               GL_LUMINANCE, or GL_LUMINANCE_ALPHA.

       type    Data  type  of  components  in the output image.  Symbolic con-
               stants GL_UNSIGNED_BYTE, GL_BYTE, GL_BITMAP, GL_UNSIGNED_SHORT,
               GL_SHORT,        GL_UNSIGNED_INT,       GL_INT,       GL_FLOAT,
               GL_UNSIGNED_BYTE_3_3_2,             GL_UNSIGNED_BYTE_2_3_3_REV,
               GL_UNSIGNED_SHORT_5_6_5,           GL_UNSIGNED_SHORT_5_6_5_REV,
               GL_UNSIGNED_SHORT_4_4_4_4,       GL_UNSIGNED_SHORT_4_4_4_4_REV,
               GL_UNSIGNED_SHORT_5_5_5_1,       GL_UNSIGNED_SHORT_1_5_5_5_REV,
               GL_UNSIGNED_INT_8_8_8_8,           GL_UNSIGNED_INT_8_8_8_8_REV,
               GL_UNSIGNED_INT_10_10_10_2,  and GL_UNSIGNED_INT_2_10_10_10_REV
               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  GL_ARB_imaging  is  returned
       when glGetString is called with an argument of GL_EXTENSIONS.

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

ERRORS

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

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

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

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

       GL_INVALID_OPERATION    is    generated    if    type    is    one   of
       GL_UNSIGNED_BYTE_3_3_2,                     GL_UNSIGNED_BYTE_2_3_3_REV,
       GL_UNSIGNED_SHORT_5_6_5,  or  GL_UNSIGNED_SHORT_5_6_5_REV and format is
       not GL_RGB.

       GL_INVALID_OPERATION   is    generated    if    type    is    one    of
       GL_UNSIGNED_SHORT_4_4_4_4,               GL_UNSIGNED_SHORT_4_4_4_4_REV,
       GL_UNSIGNED_SHORT_5_5_5_1,               GL_UNSIGNED_SHORT_1_5_5_5_REV,
       GL_UNSIGNED_INT_8_8_8_8,                   GL_UNSIGNED_INT_8_8_8_8_REV,
       GL_UNSIGNED_INT_10_10_10_2, or GL_UNSIGNED_INT_2_10_10_10_REV and  for-
       mat is neither GL_RGBA nor GL_BGRA.

ASSOCIATED GETS

       glGetConvolutionParameter

SEE ALSO

       glGetSeparableFilter(3G),                   glConvolutionParameter(3G),
       glConvolutionFilter1D(3G), glConvolutionFilter2D(3G)

                                                    GLGETCONVOLUTIONFILTER(3G)