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.
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
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 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.
