GLCONVOLUTIONPARAMETER(3G) GLCONVOLUTIONPARAMETER(3G)
NAME
glConvolutionParameterf, glConvolutionParameteri, glConvolutionParameterfv, glConvolutionParameteriv
- set convolution parameters
C SPECIFICATION
void glConvolutionParameterf( GLenum target,
GLenum pname,
GLfloat params )
void glConvolutionParameteri( GLenum target,
GLenum pname,
GLint params )
PARAMETERS
target The target for the convolution parameter. Must be one of GL_CONVOLUTION_1D,
GL_CONVOLUTION_2D, or GL_SEPARABLE_2D.
pname The parameter to be set. Must be GL_CONVOLUTION_BORDER_MODE.
params The parameter value. Must be one of GL_REDUCE, GL_CONSTANT_BORDER, GL_REPLICATE_BORDER.
C SPECIFICATION
void glConvolutionParameterfv( GLenum target,
GLenum pname,
const GLfloat *params )
void glConvolutionParameteriv( GLenum target,
GLenum pname,
const GLint *params )
PARAMETERS
target The target for the convolution parameter. Must be one of GL_CONVOLUTION_1D,
GL_CONVOLUTION_2D, or GL_SEPARABLE_2D.
pname The parameter to be set. Must be one of GL_CONVOLUTION_BORDER_MODE,
GL_CONVOLUTION_BORDER_COLOR, GL_CONVOLUTION_FILTER_SCALE, or GL_CONVOLUTION_FILTER_BIAS.
params The parameter value. If pname is GL_CONVOLUTION_BORDER_MODE, params must be one of GL_REDUCE,
GL_CONSTANT_BORDER, or GL_REPLICATE_BORDER. Otherwise, must be a vector of four values (for
red, green, blue, and alpha, respectively) to be used for scaling (when pname is
GL_CONVOLUTION_FILTER_SCALE), or biasing (when pname is GL_CONVOLUTION_FILTER_BIAS) a convolu-tion convolution
tion filter kernel or setting the constant border color (when pname is
GL_CONVOLUTION_BORDER_COLOR.
DESCRIPTION
glConvolutionParameter sets the value of a convolution parameter.
target selects the convolution filter to be affected: GL_CONVOLUTION_1D, GL_CONVOLUTION_2D, or
GL_SEPARABLE_2D for the 1D, 2D, or separable 2D filter, respectively.
pname selects the parameter to be changed. GL_CONVOLUTION_FILTER_SCALE and
GL_CONVOLUTION_FILTER_BIAS affect the definition of the convolution filter kernel; see
glConvolutionFilter1D, glConvolutionFilter2D, and glSeparableFilter2D for details. In these cases,
params is an array of four values to be applied to red, green, blue, and alpha values, respectively.
The initial value for GL_CONVOLUTION_FILTER_SCALE is (1, 1, 1, 1), and the initial value for
GL_CONVOLUTION_FILTER_BIAS is (0, 0, 0, 0).
A pname value of GL_CONVOLUTION_BORDER_MODE controls the convolution border mode. The accepted modes
are:
GL_REDUCE
The image resulting from convolution is smaller than the source image. If the filter width is
Wf and height is Hf, and the source image width is Ws and height is Hs, then the convolved
image width will be Ws - Wf + 1 and height will be Hs - Hf + 1. (If this reduction would gen-erate generate
erate an image with zero or negative width and/or height, the output is simply null, with no
error generated.) The coordinates of the image resulting from convolution are zero through Ws
- Wf in width and zero through Hs - Hf in height.
GL_CONSTANT_BORDER
The image resulting from convolution is the same size as the source image, and processed as if
the source image were surrounded by pixels with their color specified by the
GL_CONVOLUTION_BORDER_COLOR.
GL_REPLICATE_BORDER
The image resulting from convolution is the same size as the source image, and processed as if
the outermost pixel on the border of the source image were replicated.
NOTES
glConvolutionParameter is present only if GL_ARB_imaging is returned when glGetString is called with
an argument of GL_EXTENSIONS.
In cases where errors can result from the specification of invalid image dimensions, it is the dimen-sions dimensions
sions after convolution that are tested, not the dimensions of the source image. For example,
glTexImage1D requires power-of-two image size. When GL_REDUCE border mode is in effect, the source
image must be larger than the final power-of-two size by one less than the size of the 1D filter ker-nel. kernel.
nel.
ERRORS
GL_INVALID_ENUM is generated if target is not one of the allowable values.
GL_INVALID_ENUM is generated if pname is not one of the allowable values.
GL_INVALID_ENUM is generated if pname is GL_CONVOLUTION_BORDER_MODE and params is not one of
GL_REDUCE, GL_CONSTANT_BORDER, or GL_REPLICATE_BORDER.
GL_INVALID_OPERATION is generated if glConvolutionParameter is executed between the execution of
glBegin and the corresponding execution of glEnd.
ASSOCIATED GETS
glGetConvolutionParameter
SEE ALSO
glConvolutionFilter1D(3G), glConvolutionFilter2D(3G), glSeparableFilter2D(3G), glGetConvolutionParameter(3G)
GLCONVOLUTIONPARAMETER(3G)
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