glCopyConvolutionFilter2D(3G) OpenGL Reference glCopyConvolutionFilter2D(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 format 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.
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 convolution 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.
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
Page 1
glCopyConvolutionFilter2D(3G) OpenGL Reference glCopyConvolutionFilter2D(3G)
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 format 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 format
(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
format.
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 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.
glCopyConvolutionFilter2D 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.
Page 2
glCopyConvolutionFilter2D(3G) OpenGL Reference glCopyConvolutionFilter2D(3G)
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, glConvolutionParameter, glPixelTransfer
PPPPaaaaggggeeee 3333 [ Back ]
|
