glCopyConvolutionFilter1DEXT(3G) OpenGL Reference
NAME
glCopyConvolutionFilter1DEXT - copy pixels into a one-dimensional
convolution filter
C SPECIFICATION
void glCopyConvolutionFilter1DEXT( GLenum target,
GLenum internalformat,
GLint x,
GLint y,
GLsizei width )
PARAMETERS
target Must be GLCONVOLUTION1DEXT.
internalformat The internal format of the convolution filter kernel.
The allowable values are GLALPHA, GLLUMINANCE,
GLLUMINANCEALPHA, GLINTENSITYEXT, GLRGB, and
GLRGBA.
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
glCopyConvolutionFilter1DEXT defines a one-dimensional convolution filter
kernel with pixels from the current GLREADBUFFER (rather than from main
memory, as is the case for glConvolutionFilter1DEXT).
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 glReadPixels 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 GLCONVOLUTIONFILTERSCALEEXT parameters and
biased by the four 1D GLCONVOLUTIONFILTERBIASEXT parameters. (The
scale and bias parameters are set by glConvolutionParameterEXT using the
GLCONVOLUTION1DEXT target and the names
GLCONVOLUTIONFILTERSCALEEXT and GLCONVOLUTIONFILTERBIASEXT. 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.
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glCopyConvolutionFilter1DEXT(3G) OpenGL Reference
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
_______________________________________________________________________
GLALPHA A
GLLUMINANCE R
GLLUMINANCEALPHA A R
GLINTENSITYEXT R
GLRGB R G B
GLRGBA 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
GLPOSTCONVOLUTIONcSCALEEXT parameters and biased by their
corresponding GLPOSTCONVOLUTIONcBIASEXT parameters (where c takes on
the values RED, GREEN, BLUE, and ALPHA). These parameters are set by
glPixelTransfer.
NOTES
glCopyConvolutionFilter1DEXT is part of the EXTconvolution extension.
See glIntro for more information about using extensions.
ERRORS
GLINVALIDENUM is generated if target is not GLCONVOLUTION1DEXT.
GLINVALIDENUM is generated if internalformat is not one of the
allowable values.
GLINVALIDVALUE is generated if width is less than zero or greater than
the maximum supported value. This value may be queried with
glGetConvolutionParameterEXT using target GLCONVOLUTION1DEXT and name
GLMAXCONVOLUTIONWIDTHEXT.
GLINVALIDOPERATION is generated if glCopyConvolutionFilter1DEXT is
executed between the execution of glBegin and the corresponding execution
of glEnd.
ASSOCIATED GETS
glGetConvolutionParameterEXT, glGetConvolutionFilterEXT
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glCopyConvolutionFilter1DEXT(3G) OpenGL Reference
MACHINE DEPENDENCIES
glCopyConvolutionFilter1DEXT is not supported on RealityEngine,
RealityEngine2, and VTX systems.
SEE ALSO
glConvolutionFilter1DEXT, glConvolutionParameterEXT, glEnable with
parameter GLCONVOLUTION1DEXT, glPixelTransfer.
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