GLCOPYCONVOLUTIONFILTUNIX(ProgrammerGLCOPYCONVOLUTIONFILTER2D(3G)
glCopyConvolutionFilter2D - copy pixels into a two-
dimensional convolution filter
void glCopyConvolutionFilter2D( GLenum target,
GLenum internalformat,
GLint x,
GLint y,
GLsizei width,
GLsizei height )
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.
x, y The window space coordinates of the lower-
left coordinate of the pixel array to copy.
width The width of the pixel array to copy.
height The height of the pixel array to copy.
glCopyConvolutionFilter2D defines a two-dimensional convolu-
tion filter kernel with pixels from the current
GL_READ_BUFFER (rather than from main memory, as is the case
for glConvolutionFilter2D).
The screen-aligned pixel rectangle with lower-left corner at
(x, y), width width and height height is used to define the
convolution filter. If any pixels within this region are
outside the window that is associated with the GL context,
the values obtained for those pixels are undefined.
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GLCOPYCONVOLUTIONFILTUNIX(ProgrammerGLCOPYCONVOLUTIONFILTER2D(3G)
The pixels in the rectangle are processed exactly as if
glReadPixels had been called with format set to RGBA, but
the process stops just before final conversion. 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:
The red, green, blue, alpha, luminance, and/or intensity
components of the resulting pixels are stored in floating-
point rather than integer
Pixel ordering is such that lower x screen coordinates
correspond to lower i filter image coordinates, and lower y
screen coordinates correspond to lower j filter image coor-
dinates.
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.
glCopyConvolutionFilter2D is present only if GL_ARB_imaging
is returned when glGetString is called with an argument of
GL_EXTENSIONS.
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GLCOPYCONVOLUTIONFILTUNIX(ProgrammerGLCOPYCONVOLUTIONFILTER2D(3G)
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_OPERATION is generated if
glCopyConvolutionFilter2D is executed between the execution
of glBegin and the corresponding execution of glEnd.
glGetConvolutionParameter, glGetConvolutionFilter
glConvolutionFilter2D(3G), glConvolutionParameter(3G),
glPixelTransfer(3G)
MirOS BSD #10-current Printed 20.2.2012 3
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