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<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook MathML Module V1.1b1//EN"
"http://www.oasis-open.org/docbook/xml/mathml/1.1CR1/dbmathml.dtd">
<refentry id="glConvolutionParameter">
<refmeta>
<refmetainfo>
<copyright>
<year>1991-2006</year>
<holder>Silicon Graphics, Inc.</holder>
</copyright>
</refmetainfo>
<refentrytitle>glConvolutionParameter</refentrytitle>
<manvolnum>3G</manvolnum>
</refmeta>
<refnamediv>
<refname>glConvolutionParameter</refname>
<refpurpose>set convolution parameters</refpurpose>
</refnamediv>
<refsynopsisdiv><title>C Specification</title>
<funcsynopsis>
<funcprototype>
<funcdef>void <function>glConvolutionParameterf</function></funcdef>
<paramdef>GLenum <parameter>target</parameter></paramdef>
<paramdef>GLenum <parameter>pname</parameter></paramdef>
<paramdef>GLfloat <parameter>params</parameter></paramdef>
</funcprototype>
</funcsynopsis>
<funcsynopsis>
<funcprototype>
<funcdef>void <function>glConvolutionParameteri</function></funcdef>
<paramdef>GLenum <parameter>target</parameter></paramdef>
<paramdef>GLenum <parameter>pname</parameter></paramdef>
<paramdef>GLint <parameter>params</parameter></paramdef>
</funcprototype>
</funcsynopsis>
</refsynopsisdiv>
<!-- eqn: ignoring delim $$ -->
<para>
</para>
<refsect1 id="parameters"><title>Parameters</title>
<variablelist>
<varlistentry>
<term><parameter>target</parameter></term>
<listitem>
<para>
The target for the convolution parameter.
Must be one of
<constant>GL_CONVOLUTION_1D</constant>,
<constant>GL_CONVOLUTION_2D</constant>, or
<constant>GL_SEPARABLE_2D</constant>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>pname</parameter></term>
<listitem>
<para>
The parameter to be set.
Must be
<constant>GL_CONVOLUTION_BORDER_MODE</constant>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>params</parameter></term>
<listitem>
<para>
The parameter value.
Must be one of
<constant>GL_REDUCE</constant>, <constant>GL_CONSTANT_BORDER</constant>, <constant>GL_REPLICATE_BORDER</constant>.
</para>
<para>
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsynopsisdiv><title>C Specification</title>
<funcsynopsis>
<funcprototype>
<funcdef>void <function>glConvolutionParameterfv</function></funcdef>
<paramdef>GLenum <parameter>target</parameter></paramdef>
<paramdef>GLenum <parameter>pname</parameter></paramdef>
<paramdef>const GLfloat * <parameter>params</parameter></paramdef>
</funcprototype>
</funcsynopsis>
<funcsynopsis>
<funcprototype>
<funcdef>void <function>glConvolutionParameteriv</function></funcdef>
<paramdef>GLenum <parameter>target</parameter></paramdef>
<paramdef>GLenum <parameter>pname</parameter></paramdef>
<paramdef>const GLint * <parameter>params</parameter></paramdef>
</funcprototype>
</funcsynopsis>
</refsynopsisdiv>
<para>
</para>
<refsect1 id="parameters2"><title>Parameters</title>
<variablelist>
<varlistentry>
<term><parameter>target</parameter></term>
<listitem>
<para>
The target for the convolution parameter.
Must be one of
<constant>GL_CONVOLUTION_1D</constant>,
<constant>GL_CONVOLUTION_2D</constant>, or
<constant>GL_SEPARABLE_2D</constant>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>pname</parameter></term>
<listitem>
<para>
The parameter to be set.
Must be one of
<constant>GL_CONVOLUTION_BORDER_MODE</constant>,
<constant>GL_CONVOLUTION_BORDER_COLOR</constant>,
<constant>GL_CONVOLUTION_FILTER_SCALE</constant>, or
<constant>GL_CONVOLUTION_FILTER_BIAS</constant>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>params</parameter></term>
<listitem>
<para>
The parameter value.
If <parameter>pname</parameter>v is <constant>GL_CONVOLUTION_BORDER_MODE</constant>, <parameter>params</parameter>v must be one of
<constant>GL_REDUCE</constant>, <constant>GL_CONSTANT_BORDER</constant>, or <constant>GL_REPLICATE_BORDER</constant>.
Otherwise, must be a vector of four values (for red, green, blue, and alpha,
respectively) to be used for
scaling (when <parameter>pname</parameter>v is <constant>GL_CONVOLUTION_FILTER_SCALE</constant>), or
biasing (when <parameter>pname</parameter>v is <constant>GL_CONVOLUTION_FILTER_BIAS</constant>) a convolution
filter kernel or setting the constant border color (when <parameter>pname</parameter>v is
<constant>GL_CONVOLUTION_BORDER_COLOR</constant>.
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1 id="description"><title>Description</title>
<para>
<function>glConvolutionParameter</function> sets the value of a convolution parameter.
</para>
<para>
<parameter>target</parameter> selects the convolution filter to be affected:
<constant>GL_CONVOLUTION_1D</constant>,
<constant>GL_CONVOLUTION_2D</constant>, or
<constant>GL_SEPARABLE_2D</constant>
for the 1D, 2D, or separable 2D filter, respectively.
</para>
<para>
<parameter>pname</parameter> selects the parameter to be changed.
<constant>GL_CONVOLUTION_FILTER_SCALE</constant> and <constant>GL_CONVOLUTION_FILTER_BIAS</constant>
affect the definition of the convolution filter kernel; see
<citerefentry><refentrytitle>glConvolutionFilter1D</refentrytitle></citerefentry>, <citerefentry><refentrytitle>glConvolutionFilter2D</refentrytitle></citerefentry>, and
<citerefentry><refentrytitle>glSeparableFilter2D</refentrytitle></citerefentry> for details.
In these cases, <parameter>params</parameter>v is an array of four values to be applied to
red, green, blue, and alpha values, respectively. The initial value for
<constant>GL_CONVOLUTION_FILTER_SCALE</constant> is (1, 1, 1, 1), and the initial value
for <constant>GL_CONVOLUTION_FILTER_BIAS</constant> is (0, 0, 0, 0).
</para>
<para>
A <parameter>pname</parameter> value of <constant>GL_CONVOLUTION_BORDER_MODE</constant> controls the
convolution border mode. The accepted modes are:
</para>
<variablelist>
<varlistentry>
<term><constant>GL_REDUCE</constant></term>
<listitem>
<para>
The image resulting from convolution is
smaller than the source image.
If the filter width is
<inlineequation><mml:math><mml:mi mathvariant="italic">Wf</mml:mi></mml:math></inlineequation>
and height is
<inlineequation><mml:math><mml:mi mathvariant="italic">Hf</mml:mi></mml:math></inlineequation>,
and the source image width is
<inlineequation><mml:math><mml:mi mathvariant="italic">Ws</mml:mi></mml:math></inlineequation>
and height is
<inlineequation><mml:math><mml:mi mathvariant="italic">Hs</mml:mi></mml:math></inlineequation>,
then the convolved image width will be
<inlineequation><mml:math>
<!-- eqn: Ws - Wf + 1:-->
<mml:mrow>
<mml:mi mathvariant="italic">Ws</mml:mi>
<mml:mo>-</mml:mo>
<mml:mi mathvariant="italic">Wf</mml:mi>
<mml:mo>+</mml:mo>
<mml:mn>1</mml:mn>
</mml:mrow>
</mml:math></inlineequation>
and height
will be
<inlineequation><mml:math>
<!-- eqn: Hs - Hf + 1:-->
<mml:mrow>
<mml:mi mathvariant="italic">Hs</mml:mi>
<mml:mo>-</mml:mo>
<mml:mi mathvariant="italic">Hf</mml:mi>
<mml:mo>+</mml:mo>
<mml:mn>1</mml:mn>
</mml:mrow>
</mml:math></inlineequation>.
(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
<inlineequation><mml:math>
<!-- eqn: Ws - Wf:-->
<mml:mrow>
<mml:mi mathvariant="italic">Ws</mml:mi>
<mml:mo>-</mml:mo>
<mml:mi mathvariant="italic">Wf</mml:mi>
</mml:mrow>
</mml:math></inlineequation>
in width and zero through
<inlineequation><mml:math>
<!-- eqn: Hs - Hf:-->
<mml:mrow>
<mml:mi mathvariant="italic">Hs</mml:mi>
<mml:mo>-</mml:mo>
<mml:mi mathvariant="italic">Hf</mml:mi>
</mml:mrow>
</mml:math></inlineequation>
in
height.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>GL_CONSTANT_BORDER</constant></term>
<listitem>
<para>
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 <constant>GL_CONVOLUTION_BORDER_COLOR</constant>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>GL_REPLICATE_BORDER</constant></term>
<listitem>
<para>
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.
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1 id="notes"><title>Notes</title>
<para>
<function>glConvolutionParameter</function> is present only if <code>ARB_imaging</code> is returned when <citerefentry><refentrytitle>glGetString</refentrytitle></citerefentry>
is called with an argument of <constant>GL_EXTENSIONS</constant>.
</para>
<para>
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, <citerefentry><refentrytitle>glTexImage1D</refentrytitle></citerefentry> requires power-of-two image size.
When <constant>GL_REDUCE</constant> 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.
</para>
</refsect1>
<refsect1 id="errors"><title>Errors</title>
<para>
<constant>GL_INVALID_ENUM</constant> is generated if <parameter>target</parameter> is not one of the allowable
values.
</para>
<para>
<constant>GL_INVALID_ENUM</constant> is generated if <parameter>pname</parameter> is not one of the allowable
values.
</para>
<para>
<constant>GL_INVALID_ENUM</constant> is generated if <parameter>pname</parameter> is
<constant>GL_CONVOLUTION_BORDER_MODE</constant> and <parameter>params</parameter> is not one of
<constant>GL_REDUCE</constant>, <constant>GL_CONSTANT_BORDER</constant>, or <constant>GL_REPLICATE_BORDER</constant>.
</para>
<para>
<constant>GL_INVALID_OPERATION</constant> is generated if <function>glConvolutionParameter</function> is executed
between the execution of <citerefentry><refentrytitle>glBegin</refentrytitle></citerefentry> and the corresponding
execution of <citerefentry><refentrytitle>glEnd</refentrytitle></citerefentry>.
</para>
</refsect1>
<refsect1 id="associatedgets"><title>Associated Gets</title>
<para>
<citerefentry><refentrytitle>glGetConvolutionParameter</refentrytitle></citerefentry>
</para>
</refsect1>
<refsect1 id="seealso"><title>See Also</title>
<para>
<citerefentry><refentrytitle>glConvolutionFilter1D</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glConvolutionFilter2D</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glSeparableFilter2D</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glGetConvolutionParameter</refentrytitle></citerefentry>
</para>
</refsect1>
<refsect1 id="Copyright"><title>Copyright</title>
<para>
Copyright <trademark class="copyright"></trademark> 1991-2006
Silicon Graphics, Inc. This document is licensed under the SGI
Free Software B License. For details, see
<ulink url="http://oss.sgi.com/projects/FreeB/">http://oss.sgi.com/projects/FreeB/</ulink>.
</para>
</refsect1>
</refentry>