fglGetConvolutionFilter(3G)

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


FORTRAN SPECIFICATION
     SUBROUTINE fglGetConvolutionFilter( INTEGER*4 target,
                                         INTEGER*4 format,
                                         INTEGER*4 type,
                                         CHARACTER*8 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_ABGR_EXT,
             GL_LUMINANCE, or GL_LUMINANCE_ALPHA.

     type    Data type of components in the output image.  Symbolic constants
             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
     fglGetConvolutionFilter 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 format 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
     fglGetConvolutionFilter is present only if GL_ARB_imaging is returned
     when fglGetString is called with an argument of GL_EXTENSIONS.

     GL_ABGR_EXT is valid only if the EXT_abgr extension is supported.

     The current separable 2D filter must be retrieved with
     fglGetSeparableFilter rather than fglGetConvolutionFilter.

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

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

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

     GL_INVALID_OPERATION is generated if fglGetConvolutionFilter is executed
     between the execution of fglBegin and the corresponding execution of
     fglEnd.

     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 format
     is not GL_RGBA, GL_BGRA or GL_ABGR_EXT.

ASSOCIATED GETS
     fglGetConvolutionParameter
SEE ALSO
     fglGetSeparableFilter, fglConvolutionParameter, fglConvolutionFilter1D,
     fglConvolutionFilter2D