fglCopyConvolutionFilter1DEXT(3G)

NAME
     fglCopyConvolutionFilter1DEXT - copy pixels into a one-dimensional
     convolution filter


FORTRAN SPECIFICATION
     SUBROUTINE fglCopyConvolutionFilter1DEXT( INTEGER*4 target,
                                               INTEGER*4 internalformat,
                                               INTEGER*4 x,
                                               INTEGER*4 y,
                                               INTEGER*4 width )


PARAMETERS
     target          Must be GL_CONVOLUTION_1D_EXT.

     internalformat  The internal format of the convolution filter kernel.
                     The allowable values are GL_ALPHA, GL_LUMINANCE,
                     GL_LUMINANCE_ALPHA, GL_INTENSITY_EXT, GL_RGB, and
                     GL_RGBA.

     x               The x coordinate of the lower-left coordinate of the
                     pixel array to copy.

     y               The y coordinate of the lower-left coordinate of the
                     pixel array to copy.

     width           The width of the pixel array to copy.

DESCRIPTION
     fglCopyConvolutionFilter1DEXT defines a one-dimensional convolution
     filter kernel with pixels from the current GL_READ_BUFFER (rather than
     from main memory, as is the case for fglConvolutionFilter1DEXT).

     The screen-aligned pixel rectangle with lower-left corner at (x, y),
     width width+2*border and height 1 is used to define the convolution
     filter.  If any pixels within this region are outside the window that is
     associated with the GL context, the values obtained for those pixels are
     undefined.

     The pixels in the rectangle are processed exactly as if fglReadPixels had
     been called with format set to RGBA, but the process stops just before
     final conversion. The R, G, B, and A components of each pixel are next
     scaled by the four 1D GL_CONVOLUTION_FILTER_SCALE_EXT parameters and
     biased by the four 1D GL_CONVOLUTION_FILTER_BIAS_EXT parameters.  (The
     scale and bias parameters are set by fglConvolutionParameterEXT using the
     GL_CONVOLUTION_1D_EXT target and the names
     GL_CONVOLUTION_FILTER_SCALE_EXT and GL_CONVOLUTION_FILTER_BIAS_EXT.  The
     parameters themselves are vectors of four values that are applied to red,
     green, blue, and alpha, in that order.)  The R, G, B, and A values are
     not clamped to [0,1] at any time during this process.
     Each pixel is then converted to the internal format specified by
     internalformat.  This conversion simply maps the component values of the
     pixel (R, G, B, and A) to the values included in the internal format
     (red, green, blue, alpha, luminance, and intensity).  The mapping is as
     follows:

      Internal Format      Red   Green   Blue   Alpha   Luminance   Intensity
      _______________________________________________________________________
      GL_ALPHA                                    A
      GL_LUMINANCE                                R
      GL_LUMINANCE_ALPHA                  A       R
      GL_INTENSITY_EXT                                                  R
      GL_RGB                R      G      B
      GL_RGBA               R      G      B       A

     The red, green, blue, alpha, luminance, and/or intensity components of
     the resulting pixels are stored in floating-point rather than integer
     format.

     Pixel ordering is such that lower x screen coordinates correspond to
     lower i filter image coordinates.

     Note that after a convolution is performed, the resulting color
     components are also scaled by their corresponding
     GL_POST_CONVOLUTION_c_SCALE_EXT parameters and biased by their
     corresponding GL_POST_CONVOLUTION_c_BIAS_EXT parameters (where c takes on
     the values RED, GREEN, BLUE, and ALPHA).  These parameters are set by
     fglPixelTransfer.

NOTES
     fglCopyConvolutionFilter1DEXT is part of the EXT_convolution extension.
     See fglIntro for more information about using extensions.

ERRORS
     GL_INVALID_ENUM is generated if target is not GL_CONVOLUTION_1D_EXT.

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

     GL_INVALID_VALUE is generated if width is less than zero or greater than
     the maximum supported value.  This value may be queried with
     fglGetConvolutionParameterEXT using target GL_CONVOLUTION_1D_EXT and name
     GL_MAX_CONVOLUTION_WIDTH_EXT.

     GL_INVALID_OPERATION is generated if fglCopyConvolutionFilter1DEXT is
     executed between the execution of fglBegin and the corresponding
     execution of fglEnd.

ASSOCIATED GETS
     fglGetConvolutionParameterEXT, fglGetConvolutionFilterEXT

MACHINE DEPENDENCIES
     fglCopyConvolutionFilter1DEXT is not supported on RealityEngine,
     RealityEngine2, and VTX systems.


SEE ALSO
     fglConvolutionFilter1DEXT, fglConvolutionParameterEXT, fglEnable with
     parameter GL_CONVOLUTION_1D_EXT, fglPixelTransfer.