GLCONVOLUTIONFILTER2DUNIX Programmer's MGLCONVOLUTIONFILTER2D(3G)
glConvolutionFilter2D - define a two-dimensional convolution
filter
void glConvolutionFilter2D( GLenum target,
GLenum internalformat,
GLsizei width,
GLsizei height,
GLenum format,
GLenum type,
const GLvoid *image )
target Must be GL_CONVOLUTION_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 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 allow-
able 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. 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,
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GLCONVOLUTIONFILTER2DUNIX Programmer's MGLCONVOLUTIONFILTER2D(3G)
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 convolu-
tion filter kernel.
glConvolutionFilter2D builds a two-dimensional convolution
filter kernel 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 completed.
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 parameters 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
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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GLCONVOLUTIONFILTER2DUNIX Programmer's MGLCONVOLUTIONFILTER2D(3G)
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 coordinates 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 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.
glConvolutionFilter2D is present only if GL_ARB_imaging is
returned when glGetString is called with an argument of
GL_EXTENSIONS.
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 values.
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.
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GLCONVOLUTIONFILTER2DUNIX Programmer's MGLCONVOLUTIONFILTER2D(3G)
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.
glGetConvolutionParameter, glGetConvolutionFilter
glConvolutionFilter1D(3G), glSeparableFilter2D(3G),
glConvolutionParameter(3G), glPixelTransfer(3G)
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