glConvolutionFilter2D
GLCONVOLUTIONFILTER2D(3G) GLCONVOLUTIONFILTER2D(3G)
NAME
glConvolutionFilter2D - define a two-dimensional convolution filter
C SPECIFICATION
void glConvolutionFilter2D( GLenum target,
GLenum internalformat,
GLsizei width,
GLsizei height,
GLenum format,
GLenum type,
const GLvoid *image )
PARAMETERS
target Must be GL_CONVOLUTION_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 width of the pixel array referenced by image.
height The height of the pixel array referenced by image.
format The of the pixel data in image. The allowable values
are GL_RED, GL_GREEN, GL_BLUE, GL_ALPHA, GL_RGB,
GL_BGR, GL_RGBA, GL_BGRA, GL_LUMINANCE, and
GL_LUMINANCE_ALPHA.
type The type of the pixel data in image. Symbolic con-
stants 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.
image Pointer to a two-dimensional array of pixel data that
is processed to build the convolution filter kernel.
DESCRIPTION
glConvolutionFilter2D builds a two-dimensional convolution filter ker-
nel from an array of pixels.
The pixel array specified by width, height, format, type, and image is
extracted from memory and processed just as if glDrawPixels were
called, but processing stops after the final expansion to RGBA is com-
pleted.
The R, G, B, and A components of each pixel are next scaled by the
four 2D GL_CONVOLUTION_FILTER_SCALE parameters and biased by the four
2D GL_CONVOLUTION_FILTER_BIAS parameters. (The scale and bias parame-
ters are set by glConvolutionParameter using the GL_CONVOLUTION_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 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_ALPHA A
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 a two-dimensional filter kernel image indexed with coordi-
nates i and j such that i starts at zero and increases from left to
right, and j starts at zero and increases from bottom to top. Kernel
location i,j is derived from the Nth pixel, where N is i+j*width.
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
glConvolutionFilter2D 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_CONVOLUTION_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_CONVOLUTION_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_CONVOLUTION_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 glConvolutionFilter2D 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, glGetConvolutionFilter
SEE ALSO
glConvolutionFilter1D(3G), glSeparableFilter2D(3G),
glConvolutionParameter(3G), glPixelTransfer(3G)
GLCONVOLUTIONFILTER2D(3G)
