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 )
delim $$
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 convolution filter
kernel or setting the constant border color (when pname is
GL_CONVOLUTION_BORDER_COLOR.
DESCRIPTIONglConvolutionParameter 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 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.
NOTESglConvolutionParameter 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 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 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 ALSOglConvolutionFilter1D(3G), glConvolutionFilter2D(3G),
glSeparableFilter2D(3G), glGetConvolutionParameter(3G)
March 1, 2011
