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