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 GL_SEPARABLE_2D.
internalformat The internal of the convolution filter kernel. The allowable values are GL_ALPHA,
GL_ALPHA4, GL_ALPHA8, GL_ALPHA12, GL_ALPHA16, GL_LUMINANCE, GL_LUMINANCE4,
GL_LUMINANCE8, GL_LUMINANCE12, GL_LUMINANCE16, GL_LUMINANCE_ALPHA,
GL_LUMINANCE4_ALPHA4, GL_LUMINANCE6_ALPHA2, GL_LUMINANCE8_ALPHA8,
GL_LUMINANCE12_ALPHA4, GL_LUMINANCE12_ALPHA12, GL_LUMINANCE16_ALPHA16, GL_INTENSITY,
GL_INTENSITY4, GL_INTENSITY8, GL_INTENSITY12, GL_INTENSITY16, GL_R3_G3_B2, GL_RGB,
GL_RGB4, GL_RGB5, GL_RGB8, GL_RGB10, GL_RGB12, GL_RGB16, GL_RGBA, GL_RGBA2, GL_RGBA4,
GL_RGB5_A1, GL_RGBA8, GL_RGB10_A2, GL_RGBA12, or GL_RGBA16.
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 of the pixel data in row and column. The allowable values are GL_RED, GL_GREEN,
GL_BLUE, GL_ALPHA, GL_RGB, GL_BGR, GL_RGBA, GL_BGRA, GL_INTENSITY, GL_LUMINANCE, and
GL_LUMINANCE_ALPHA.
type The type of the pixel data in row and column. Symbolic constants GL_UNSIGNED_BYTE,
GL_BYTE, GL_BITMAP, GL_UNSIGNED_SHORT, GL_SHORT, GL_UNSIGNED_INT, GL_INT, GL_FLOAT,
GL_UNSIGNED_BYTE_3_3_2, GL_UNSIGNED_BYTE_2_3_3_REV, GL_UNSIGNED_SHORT_5_6_5,
GL_UNSIGNED_SHORT_5_6_5_REV, GL_UNSIGNED_SHORT_4_4_4_4,
GL_UNSIGNED_SHORT_4_4_4_4_REV, GL_UNSIGNED_SHORT_5_5_5_1,
GL_UNSIGNED_SHORT_1_5_5_5_REV, GL_UNSIGNED_INT_8_8_8_8, GL_UNSIGNED_INT_8_8_8_8_REV,
GL_UNSIGNED_INT_10_10_10_2, and GL_UNSIGNED_INT_2_10_10_10_REV 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 col-umn column
umn filter kernel.
DESCRIPTION
glSeparableFilter2D 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 pro-cessed processed
cessed just as if they had been passed to glDrawPixels, but processing stops after the final expan-sion expansion
sion 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 parameters and biased by the four separable 2D GL_CONVOLUTION_FILTER_BIAS
parameters. (The scale and bias parameters are set by glConvolutionParameter using the
GL_SEPARABLE_2D target and the names GL_CONVOLUTION_FILTER_SCALE and GL_CONVOLUTION_FILTER_BIAS. 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 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 (red,
green, blue, alpha, luminance, and intensity). The mapping is as follows:
------------------------------------------------------------------------Internal -----------------------------------------------------------------------Internal
Internal Format Red Green Blue Alpha Luminance Intensity
------------------------------------------------------------------------GL_LUMINANCE -----------------------------------------------------------------------GL_LUMINANCE
GL_LUMINANCE R
GL_LUMINANCE_ALPHA A R
GL_INTENSITY R
GL_RGB R G B
GL_RGBA R G B A
------------------------------------------------------------------------The -----------------------------------------------------------------------The
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 loca-tion location
tion 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 parameters and biased by their corresponding
GL_POST_CONVOLUTION_c_BIAS parameters (where c takes on the values RED, GREEN, BLUE, and ALPHA).
These parameters are set by glPixelTransfer.
NOTES
glSeparableFilter2D is present only if GL_ARB_imaging is returned when glGetString is called with an
argument of GL_EXTENSIONS.
ERRORS
GL_INVALID_ENUM is generated if target is not GL_SEPARABLE_2D.
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 glGetConvolutionParameter using target GL_SEPARABLE_2D and name
GL_MAX_CONVOLUTION_WIDTH.
GL_INVALID_VALUE is generated if height is less than zero or greater than the maximum supported
value. This value may be queried with glGetConvolutionParameter using target GL_SEPARABLE_2D and
name GL_MAX_CONVOLUTION_HEIGHT.
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 glSeparableFilter2D is executed between the execution of glBegin
and the corresponding execution of glEnd.
GL_INVALID_OPERATION is generated if height is one of GL_UNSIGNED_BYTE_3_3_2,
GL_UNSIGNED_BYTE_2_3_3_REV, GL_UNSIGNED_SHORT_5_6_5, or GL_UNSIGNED_SHORT_5_6_5_REV and format is not
GL_RGB.
GL_INVALID_OPERATION is generated if height is one of GL_UNSIGNED_SHORT_4_4_4_4,
GL_UNSIGNED_SHORT_4_4_4_4_REV, GL_UNSIGNED_SHORT_5_5_5_1, GL_UNSIGNED_SHORT_1_5_5_5_REV,
GL_UNSIGNED_INT_8_8_8_8, GL_UNSIGNED_INT_8_8_8_8_REV, GL_UNSIGNED_INT_10_10_10_2, or
GL_UNSIGNED_INT_2_10_10_10_REV and format is neither GL_RGBA nor GL_BGRA.
ASSOCIATED GETS
glGetConvolutionParameter, glGetSeparableFilter
SEE ALSO
glConvolutionFilter1D(3G), glConvolutionFilter2D(3G), glConvolutionParameter(3G), glPixelTransfer(3G)
GLSEPARABLEFILTER2D(3G)
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