glseparablefilter2dext - Man Page
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 GL_SEPARABLE_2D_EXT.
internalformat The internal format of the convolution filter kernel.
The allowable values are GL_LUMINANCE,
GL_LUMINANCE_ALPHA, GL_INTENSITY_EXT, GL_RGB, and
GL_RGBA.
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 GL_LUMINANCE, GL_LUMINANCE_ALPHA,
GL_RGB, GL_RGBA, and GL_ABGR_EXT.
type The type of the pixel data in row and column. The
allowable values are GL_UNSIGNED_BYTE, GL_BYTE,
GL_UNSIGNED_SHORT, GL_SHORT, GL_UNSIGNED_INT, GL_INT,
GL_FLOAT, GL_UNSIGNED_BYTE_3_3_2_EXT,
GL_UNSIGNED_SHORT_4_4_4_4_EXT,
GL_UNSIGNED_SHORT_5_5_5_1_EXT,
GL_UNSIGNED_INT_8_8_8_8_EXT, and
GL_UNSIGNED_INT_10_10_10_2_EXT.
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 GL_CONVOLUTION_FILTER_SCALE_EXT
parameters and biased by the four separable 2D
GL_CONVOLUTION_FILTER_BIAS_EXT parameters. (The scale and bias
parameters are set by glConvolutionParameterEXT using the
GL_SEPARABLE_2D_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_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. 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
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
glPixelTransfer.
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glSeparableFilter2DEXT(3G) OpenGL Reference glSeparableFilter2DEXT(3G)
ERRORS
GL_INVALID_ENUM is generated if target is not GL_SEPARABLE_2D_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
glGetConvolutionParameterEXT using target GL_SEPARABLE_2D_EXT and name
GL_MAX_CONVOLUTION_WIDTH_EXT.
GL_INVALID_VALUE is generated if height is less than zero or greater than
the maximum supported value. This value may be queried with
glGetConvolutionParameterEXT using target GL_SEPARABLE_2D_EXT and name
GL_MAX_CONVOLUTION_HEIGHT_EXT.
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 glSeparableFilter2DEXT is executed
between the execution of glBegin and the corresponding execution of
glEnd.
If type is set to GL_UNSIGNED_BYTE_3_3_2_EXT,
GL_UNSIGNED_SHORT_4_4_4_4_EXT, GL_UNSIGNED_SHORT_5_5_5_1_EXT,
GL_UNSIGNED_INT_8_8_8_8_EXT, or GL_UNSIGNED_INT_10_10_10_2_EXT and the
EXT_packed_pixels extension is not supported then a GL_INVALID_ENUM error
is generated.
ASSOCIATED GETS
glGetConvolutionParameterEXT, glGetSeparableFilter2DEXT
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
GL_INVALID_OPERATION error and do not transfer any pixels.
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glSeparableFilter2DEXT(3G) OpenGL Reference glSeparableFilter2DEXT(3G)
Loading a convolution filter with some combinations of pixel transfer
modes may be unreliable on InfiniteReality systems. Straightforward
transfers are known to work, though. The remaining problems will be
fixed in the next release.
SEE ALSO
glConvolutionFilter1DEXT, glConvolutionFilter2DEXT,
glConvolutionParameterEXT, glEnable with parameter GL_SEPARABLE_2D_EXT,
glPixelTransfer.
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