GLSEPARABLEFILTER2D(3UNIX Programmer's ManGLSEPARABLEFILTER2D(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 ker-
nel. 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,
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GLSEPARABLEFILTER2D(3UNIX Programmer's ManGLSEPARABLEFILTER2D(3G)
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 column
filter kernel.
DESCRIPTION
glSeparableFilter2D builds a two-dimensional separable con-
volution 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 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:
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GLSEPARABLEFILTER2D(3UNIX Programmer's ManGLSEPARABLEFILTER2D(3G)
_______________________________________________________________________
Internal Format Red Green Blue Alpha Luminance Intensity
_______________________________________________________________________
GL_LUMINANCE R
GL_LUMINANCE_ALPHA A R
GL_INTENSITY 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 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 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.
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GLSEPARABLEFILTER2D(3UNIX Programmer's ManGLSEPARABLEFILTER2D(3G)
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)
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