glSeparableFilter2D
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 fil-
ter kernel.)
format The of the pixel data in row and column. The allow-
able 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. Sym-
bolic 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 column 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 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 parame-
ters. (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 val-
ues are not clamped to [0,1] at any time during this process.
Each pixel is then converted to the internal specified by internal-
format. 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
------------------------------------------------------------------------
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 compo-
nents are also scaled by their corresponding
GL_POST_CONVOLUTION_c_SCALE parameters and biased by their correspond-
ing 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 val-
ues.
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 for-
mat is neither GL_RGBA nor GL_BGRA.
ASSOCIATED GETS
glGetConvolutionParameter, glGetSeparableFilter
SEE ALSO
glConvolutionFilter1D(3G), glConvolutionFilter2D(3G),
glConvolutionParameter(3G), glPixelTransfer(3G)
GLSEPARABLEFILTER2D(3G)
