GLCOPYCONVOLUTIONFILTUNIX(ProgrammerGLCOPYCONVOLUTIONFILTER1D(3G)
NAME
glCopyConvolutionFilter1D - copy pixels into a one-
dimensional convolution filter
C SPECIFICATION
void glCopyConvolutionFilter1D( GLenum target,
GLenum internalformat,
GLint x,
GLint y,
GLsizei width )
PARAMETERS
target Must be GL_CONVOLUTION_1D.
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.
DESCRIPTION
glCopyConvolutionFilter1D defines a one-dimensional convolu-
tion filter kernel with pixels from the current
GL_READ_BUFFER (rather than from main memory, as is the case
for glConvolutionFilter1D).
The screen-aligned pixel rectangle with lower-left corner at
(x, y), width width and height 1 is used to define the con-
volution filter. If any pixels within this region are out-
side the window that is associated with the GL context, the
values obtained for those pixels are undefined.
The pixels in the rectangle are processed exactly as if
glReadPixels had been called with format set to RGBA, but
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GLCOPYCONVOLUTIONFILTUNIX(ProgrammerGLCOPYCONVOLUTIONFILTER1D(3G)
the process stops just before final conversion. The R, G, B,
and A components of each pixel are next scaled by the four
1D GL_CONVOLUTION_FILTER_SCALE parameters and biased by the
four 1D GL_CONVOLUTION_FILTER_BIAS parameters. (The scale
and bias parameters are set by glConvolutionParameter using
the GL_CONVOLUTION_1D 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:
_______________________________________________________________________
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
Pixel ordering is such that lower x screen coordinates
correspond to lower i filter image coordinates.
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
glCopyConvolutionFilter1D 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_1D.
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GLCOPYCONVOLUTIONFILTUNIX(ProgrammerGLCOPYCONVOLUTIONFILTER1D(3G)
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_1D and name GL_MAX_CONVOLUTION_WIDTH.
GL_INVALID_OPERATION is generated if
glCopyConvolutionFilter1D is executed between the execution
of glBegin and the corresponding execution of glEnd.
ASSOCIATED GETS
glGetConvolutionParameter, glGetConvolutionFilter
SEE ALSO
glConvolutionFilter1D(3G), glConvolutionParameter(3G),
glPixelTransfer(3G)
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