glSeparableFilter2DEXT(3G) OpenGL Reference glSeparableFilter2DEXT(3G)
NAME
glSeparableFilter2DEXT - define a separable two-dimensional convolution
filter
C SPECIFICATION
void glSeparableFilter2DEXT( GLenum target,
GLenum internalformat,
GLsizei width,
GLsizei height,
GLenum format,
GLenum type,
const GLvoid *row,
const GLvoid *column )
PARAMETERS
target Must be GLSEPARABLE2DEXT.
internalformat The internal format of the convolution filter kernel.
The allowable values are GLLUMINANCE,
GLLUMINANCEALPHA, GLINTENSITYEXT, GLRGB, and
GLRGBA.
width The number of elements in the pixel array referenced by
row. (This is the width of the separable filter kernel.)
height The number of elements in the pixel array referenced by
column. (This is the height of the separable filter
kernel.)
format The format of the pixel data in row and column. The
allowable values are GLLUMINANCE, GLLUMINANCEALPHA,
GLRGB, GLRGBA, and GLABGREXT.
type The type of the pixel data in row and column. The
allowable values are GLUNSIGNEDBYTE, GLBYTE,
GLUNSIGNEDSHORT, GLSHORT, GLUNSIGNEDINT, GLINT,
GLFLOAT, GLUNSIGNEDBYTE332EXT,
GLUNSIGNEDSHORT4444EXT,
GLUNSIGNEDSHORT5551EXT,
GLUNSIGNEDINT8888EXT, and
GLUNSIGNEDINT1010102EXT.
row Pointer to a one-dimensional array of pixel data that is
processed to build the row filter kernel.
column Pointer to a one-dimensional array of pixel data that is
processed to build the column filter kernel.
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glSeparableFilter2DEXT(3G) OpenGL Reference glSeparableFilter2DEXT(3G)
DESCRIPTION
glSeparableFilter2DEXT builds a two-dimensional separable convolution
filter kernel from two arrays of pixels.
The pixel arrays specified by (width, format, type, row) and (height,
format, type, column) are processed just as if they had been passed to
glDrawPixels, but processing stops after the final expansion to RGBA is
completed.
Next, the R, G, B, and A components of all pixels in both arrays are
scaled by the four separable 2D GLCONVOLUTIONFILTERSCALEEXT
parameters and biased by the four separable 2D
GLCONVOLUTIONFILTERBIASEXT parameters. (The scale and bias
parameters are set by glConvolutionParameterEXT using the
GLSEPARABLE2DEXT 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.
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
_______________________________________________________________________
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. They form two one-dimensional filter kernel images. The row
image is indexed by coordinate i starting at zero and increasing from
left to right. Each location in the row image is derived from element i
of row. The column image is indexed by coordinate j starting at zero and
increasing from bottom to top. Each location in the column image is
derived from element j of column.
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.
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glSeparableFilter2DEXT(3G) OpenGL Reference glSeparableFilter2DEXT(3G)
ERRORS
GLINVALIDENUM is generated if target is not GLSEPARABLE2DEXT.
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 GLSEPARABLE2DEXT and name
GLMAXCONVOLUTIONWIDTHEXT.
GLINVALIDVALUE is generated if height is less than zero or greater than
the maximum supported value. This value may be queried with
glGetConvolutionParameterEXT using target GLSEPARABLE2DEXT and name
GLMAXCONVOLUTIONHEIGHTEXT.
GLINVALIDENUM is generated if format is not one of the allowable
values.
GLINVALIDENUM is generated if type is not one of the allowable values.
GLINVALIDOPERATION is generated if glSeparableFilter2DEXT is executed
between the execution of glBegin and the corresponding execution of
glEnd.
If type is set to GLUNSIGNEDBYTE332EXT,
GLUNSIGNEDSHORT4444EXT, GLUNSIGNEDSHORT5551EXT,
GLUNSIGNEDINT8888EXT, or GLUNSIGNEDINT1010102EXT and the
EXTpackedpixels extension is not supported then a GLINVALIDENUM error
is generated.
ASSOCIATED GETS
glGetConvolutionParameterEXT, glGetSeparableFilterEXT
MACHINE DEPENDENCIES
On RealityEngine, RealityEngine2, and VTX systems convolution may not be
used in the following circumstances:
1. When rendering to pixmaps.
2. When fragment processing (texturing, depth buffering, alpha
testing, multisampling, fog) is enabled.
3. When histogramming or minmax is enabled.
4. When either of the pixel zoom factors has a value other than 1.0
or -1.0.
In these cases, glDrawPixels and glCopyPixels report a
GLINVALIDOPERATION error and do not transfer any pixels.
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glSeparableFilter2DEXT(3G) OpenGL Reference glSeparableFilter2DEXT(3G)
SEE ALSO
glConvolutionFilter1DEXT, glConvolutionFilter2DEXT,
glConvolutionParameterEXT, glEnable with parameter GLSEPARABLE2DEXT,
glPixelTransfer.
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