GLCONVOLUTIONPARAMETEUNIX)Programmer's GLCONVOLUTIONPARAMETER(3G)
NAME
glConvolutionParameterf, glConvolutionParameteri, glConvolu-
tionParameterfv, 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.
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GLCONVOLUTIONPARAMETEUNIX)Programmer's GLCONVOLUTIONPARAMETER(3G)
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
convolution 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 generate 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 speci-
fied 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 repli-
cated.
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GLCONVOLUTIONPARAMETEUNIX)Programmer's GLCONVOLUTIONPARAMETER(3G)
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 dimensions after convo-
lution 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 kernel.
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)
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