GLSEPARABLEFILTER2D(3G) GLSEPARABLEFILTER2D(3G)
NAME
glSeparableFilter2D - define a separable two-dimensional convolution
filter
C SPECIFICATION
void glSeparableFilter2D( GLenum target,
GLenum internalformat,
GLsizei width,
GLsizei height,
GLenum format,
GLenum type,
const GLvoid *row,
const GLvoid *column )
PARAMETERS
target Must be GLSEPARABLE2D.
internalformat The internal of the convolution filter kernel. The
allowable values are GLALPHA, GLALPHA4, GLALPHA8,
GLALPHA12, GLALPHA16, GLUMINANCE, GLUMINANCE4,
GLUMINANCE8, GLUMINANCE12, GLUMINANCE16,
GLUMINANCEALPHA, GLUMINANCE4ALPHA4,
GLUMINANCE6ALPHA2, GLUMINANCE8ALPHA8,
GLUMINANCE12ALPHA4, GLUMINANCE12ALPHA12,
GLUMINANCE16ALPHA16, GLINTENSITY, GLINTENSITY4,
GLINTENSITY8, GLINTENSITY12, GLINTENSITY16,
GLR3G3B2, GLRGB, GLRGB4, GLRGB5, GLRGB8,
GLRGB100, GLRGB12, GLRGB16, GLRGBA, GLRGBA2,
GLRGBA4, GLRGB5A1, GLRGBA8, GLRGB100A2, GLRGBA12,
or GLRGBA16.
width The number of elements in the pixel array referenced by
row. (This is the width of the separable filter ker-
nel.)
height The number of elements in the pixel array referenced by
column. (This is the height of the separable filter
kernel.)
format The of the pixel data in row and column. The allow-
able values are GLRED, GLGREN, GLBLUE, GLALPHA,
GLRGB, GLBGR, GLRGBA, GLBGRA, GLINTENSITY,
GLUMINANCE, and GLUMINANCEALPHA.
type The type of the pixel data in row and column. Symbolic
constants GLUNSIGNEDBYTE, GLBYTE, GLBITMAP,
GLUNSIGNEDSHORT, GLSHORT, GLUNSIGNEDINT, GLINT,
GLFLOAT, GLUNSIGNEDBYTE332,
GLUNSIGNEDBYTE233REV, GLUNSIGNEDSHORT565,
GLUNSIGNEDSHORT565REV, GLUNSIGNEDSHORT4444,
GLUNSIGNEDSHORT4444REV,
GLUNSIGNEDSHORT5551,
GLUNSIGNEDSHORT1555REV, GLUNSIGNEDINT8888,
GLUNSIGNEDINT8888REV,
GLUNSIGNEDINT1001001002, and
GLUNSIGNEDINT2100100100REV are accepted.
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.
DESCRIPTION
glSeparableFilter2D builds a two-dimensional separable convolution fil-
ter 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 GLCONVOLUTIONFILTERSCALE parameters
and biased by the four separable 2D GLCONVOLUTIONFILTERBIAS parame-
ters. (The scale and bias parameters are set by glConvolutionParameter
using the GLSEPARABLE2D target and the names
GLCONVOLUTIONFILTERSCALE and GLCONVOLUTIONFILTERBIAS. The param-
eters 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 specified by internalfor-
mat. This conversion simply maps the component values of the pixel (R,
G, B, and A) to the values included in the internal (red, green, blue,
alpha, luminance, and intensity). The mapping is as follows:
------------------------------------------------------------------------
Internal Format Red Green Blue Alpha Luminance Intensity
------------------------------------------------------------------------
GLUMINANCE R
GLUMINANCEALPHA A R
GLINTENSITY 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
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 compo-
nents are also scaled by their corresponding
GLPOSTCONVOLUTIONcSCALE parameters and biased by their correspond-
ing GLPOSTCONVOLUTIONcBIAS parameters (where c takes on the values
RED, GREN, BLUE, and ALPHA). These parameters are set by
glPixelTransfer.
NOTES
glSeparableFilter2D is present only if GLARBimaging is returned when
glGetString is called with an argument of GLEXTENSIONS.
ERORS
GLINVALIDENUM is generated if target is not GLSEPARABLE2D.
GLINVALIDENUM is generated if internalformat is not one of the allow-
able values.
GLINVALIDVALUE is generated if width is less than zero or greater
than the maximum supported value. This value may be queried with
glGetConvolutionParameter using target GLSEPARABLE2D and name
GLMAXCONVOLUTIONWIDTH.
GLINVALIDVALUE is generated if height is less than zero or greater
than the maximum supported value. This value may be queried with
glGetConvolutionParameter using target GLSEPARABLE2D and name
GLMAXCONVOLUTIONHEIGHT.
GLINVALIDENUM is generated if format is not one of the allowable val-
ues.
GLINVALIDENUM is generated if type is not one of the allowable val-
ues.
GLINVALIDOPERATION is generated if glSeparableFilter2D is executed
between the execution of glBegin and the corresponding execution of
glEnd.
GLINVALIDOPERATION is generated if height is one of
GLUNSIGNEDBYTE332, GLUNSIGNEDBYTE233REV,
GLUNSIGNEDSHORT565, or GLUNSIGNEDSHORT565REV and format is
not GLRGB.
GLINVALIDOPERATION is generated if height is one of
GLUNSIGNEDSHORT4444, GLUNSIGNEDSHORT4444REV,
GLUNSIGNEDSHORT5551, GLUNSIGNEDSHORT1555REV,
GLUNSIGNEDINT8888, GLUNSIGNEDINT8888REV,
GLUNSIGNEDINT1001001002, or GLUNSIGNEDINT2100100100REV and for-
mat is neither GLRGBA nor GLBGRA.
ASOCIATED GETS
glGetConvolutionParameter, glGetSeparableFilter
SEE ALSO
glConvolutionFilter1D, glConvolutionFilter2D, glConvolutionParameter,
glPixelTransfer
GLSEPARABLEFILTER2D(3G)
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