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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="glCopyConvolutionFilter1D">
<refmeta>
<refmetainfo>
<copyright>
<year>1991-2006</year>
<holder>Silicon Graphics, Inc.</holder>
</copyright>
</refmetainfo>
<refentrytitle>glCopyConvolutionFilter1D</refentrytitle>
<manvolnum>3G</manvolnum>
</refmeta>
<refnamediv>
<refname>glCopyConvolutionFilter1D</refname>
<refpurpose>copy pixels into a one-dimensional convolution filter</refpurpose>
</refnamediv>
<refsynopsisdiv><title>C Specification</title>
<funcsynopsis>
<funcprototype>
<funcdef>void <function>glCopyConvolutionFilter1D</function></funcdef>
<paramdef>GLenum <parameter>target</parameter></paramdef>
<paramdef>GLenum <parameter>internalformat</parameter></paramdef>
<paramdef>GLint <parameter>x</parameter></paramdef>
<paramdef>GLint <parameter>y</parameter></paramdef>
<paramdef>GLsizei <parameter>width</parameter></paramdef>
</funcprototype>
</funcsynopsis>
</refsynopsisdiv>
<refsect1 id="parameters"><title>Parameters</title>
<variablelist>
<varlistentry>
<term><parameter>target</parameter></term>
<listitem>
<para>
Must be <constant>GL_CONVOLUTION_1D</constant>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>internalformat</parameter></term>
<listitem>
<para>
The internal format of the convolution filter kernel.
The allowable values are
<constant>GL_ALPHA</constant>,
<constant>GL_ALPHA4</constant>,
<constant>GL_ALPHA8</constant>,
<constant>GL_ALPHA12</constant>,
<constant>GL_ALPHA16</constant>,
<constant>GL_LUMINANCE</constant>,
<constant>GL_LUMINANCE4</constant>,
<constant>GL_LUMINANCE8</constant>,
<constant>GL_LUMINANCE12</constant>,
<constant>GL_LUMINANCE16</constant>,
<constant>GL_LUMINANCE_ALPHA</constant>,
<constant>GL_LUMINANCE4_ALPHA4</constant>,
<constant>GL_LUMINANCE6_ALPHA2</constant>,
<constant>GL_LUMINANCE8_ALPHA8</constant>,
<constant>GL_LUMINANCE12_ALPHA4</constant>,
<constant>GL_LUMINANCE12_ALPHA12</constant>,
<constant>GL_LUMINANCE16_ALPHA16</constant>,
<constant>GL_INTENSITY</constant>,
<constant>GL_INTENSITY4</constant>,
<constant>GL_INTENSITY8</constant>,
<constant>GL_INTENSITY12</constant>,
<constant>GL_INTENSITY16</constant>,
<constant>GL_R3_G3_B2</constant>,
<constant>GL_RGB</constant>,
<constant>GL_RGB4</constant>,
<constant>GL_RGB5</constant>,
<constant>GL_RGB8</constant>,
<constant>GL_RGB10</constant>,
<constant>GL_RGB12</constant>,
<constant>GL_RGB16</constant>,
<constant>GL_RGBA</constant>,
<constant>GL_RGBA2</constant>,
<constant>GL_RGBA4</constant>,
<constant>GL_RGB5_A1</constant>,
<constant>GL_RGBA8</constant>,
<constant>GL_RGB10_A2</constant>,
<constant>GL_RGBA12</constant>, or
<constant>GL_RGBA16</constant>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>x</parameter></term>
<term><parameter>y</parameter></term>
<listitem>
<para>
The window space coordinates of the lower-left coordinate of the
pixel array to copy.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>width</parameter></term>
<listitem>
<para>
The width of the pixel array to copy.
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1 id="description"><title>Description</title>
<para>
<function>glCopyConvolutionFilter1D</function> defines a one-dimensional convolution filter kernel with pixels
from the current <constant>GL_READ_BUFFER</constant> (rather than from main memory,
as is the case for <citerefentry><refentrytitle>glConvolutionFilter1D</refentrytitle></citerefentry>).
</para>
<para>
The screen-aligned pixel rectangle with lower-left corner at (<parameter>x</parameter>,\ <parameter>y</parameter>),
width <parameter>width</parameter> and height 1 is used to define
the convolution filter. If any pixels within this region are
outside the window that is associated with the GL context, the
values obtained for those pixels are undefined.
</para>
<para>
The pixels in the rectangle are processed exactly as if <citerefentry><refentrytitle>glReadPixels</refentrytitle></citerefentry>
had been called with <emphasis>format</emphasis>
set to RGBA, but the process stops just before final conversion.
The R, G, B, and A components of each pixel are next scaled by the four
1D <constant>GL_CONVOLUTION_FILTER_SCALE</constant> parameters and biased by the
four 1D <constant>GL_CONVOLUTION_FILTER_BIAS</constant> parameters.
(The scale and bias parameters are set by <citerefentry><refentrytitle>glConvolutionParameter</refentrytitle></citerefentry>
using the <constant>GL_CONVOLUTION_1D</constant> target and the names
<constant>GL_CONVOLUTION_FILTER_SCALE</constant> and <constant>GL_CONVOLUTION_FILTER_BIAS</constant>.
The parameters themselves are vectors of four values that are applied to red,
green, blue, and alpha, in that order.)
The R, G, B, and A values are not clamped to [0,1] at any time during this
process.
</para>
<para>
Each pixel is then converted to the internal format specified by
<parameter>internalformat</parameter>.
This conversion simply maps the component values of the pixel (R, G, B,
and A) to the values included in the internal format (red, green, blue,
alpha, luminance, and intensity). The mapping is as follows:
</para>
<para>
</para>
<informaltable frame="topbot">
<tgroup cols="7" align="left">
<colspec colwidth="3*" />
<colspec colwidth="1*" align="center"/>
<colspec colwidth="1*" align="center"/>
<colspec colwidth="1*" align="center"/>
<colspec colwidth="1*" align="center"/>
<colspec colwidth="1.7*" align="center"/>
<colspec colwidth="1.7*" align="center"/>
<thead>
<row>
<entry rowsep="1" align="left"><emphasis role="bold">
Internal Format
</emphasis></entry>
<entry rowsep="1" align="center"><emphasis role="bold">
Red
</emphasis></entry>
<entry rowsep="1" align="center"><emphasis role="bold">
Green
</emphasis></entry>
<entry rowsep="1" align="center"><emphasis role="bold">
Blue
</emphasis></entry>
<entry rowsep="1" align="center"><emphasis role="bold">
Alpha
</emphasis></entry>
<entry rowsep="1" align="center"><emphasis role="bold">
Luminance
</emphasis></entry>
<entry rowsep="1" align="center"><emphasis role="bold">
Intensity
</emphasis></entry>
</row>
</thead>
<tbody>
<row>
<entry align="left">
<constant>GL_ALPHA</constant>
</entry>
<entry align="center">
</entry>
<entry align="center">
</entry>
<entry align="center">
</entry>
<entry align="center">
A
</entry>
<entry align="center">
</entry>
<entry align="center">
</entry>
</row>
<row>
<entry align="left">
<constant>GL_LUMINANCE</constant>
</entry>
<entry align="center">
</entry>
<entry align="center">
</entry>
<entry align="center">
</entry>
<entry align="center">
</entry>
<entry align="center">
R
</entry>
<entry align="center">
</entry>
</row>
<row>
<entry align="left">
<constant>GL_LUMINANCE_ALPHA</constant>
</entry>
<entry align="center">
</entry>
<entry align="center">
</entry>
<entry align="center">
</entry>
<entry align="center">
A
</entry>
<entry align="center">
R
</entry>
<entry align="center">
</entry>
</row>
<row>
<entry align="left">
<constant>GL_INTENSITY</constant>
</entry>
<entry align="center">
</entry>
<entry align="center">
</entry>
<entry align="center">
</entry>
<entry align="center">
</entry>
<entry align="center">
</entry>
<entry align="center">
R
</entry>
</row>
<row>
<entry align="left">
<constant>GL_RGB</constant>
</entry>
<entry align="center">
R
</entry>
<entry align="center">
G
</entry>
<entry align="center">
B
</entry>
<entry align="center">
</entry>
<entry align="center">
</entry>
<entry align="center">
</entry>
</row>
<row>
<entry align="left">
<constant>GL_RGBA</constant>
</entry>
<entry align="center">
R
</entry>
<entry align="center">
G
</entry>
<entry align="center">
B
</entry>
<entry align="center">
A
</entry>
<entry align="center">
</entry>
<entry align="center">
</entry>
</row>
</tbody>
</tgroup>
</informaltable>
<para>
The red, green, blue, alpha, luminance, and/or intensity components of
the resulting pixels are stored in floating-point rather than integer
format.
</para>
<para>
Pixel ordering is such that lower x screen coordinates correspond to
lower <emphasis>i</emphasis> filter image coordinates.
</para>
<para>
Note that after a convolution is performed, the resulting color
components are also scaled by their corresponding
<constant>GL_POST_CONVOLUTION_c_SCALE</constant> parameters and biased by their
corresponding <constant>GL_POST_CONVOLUTION_c_BIAS</constant> parameters (where
<emphasis>c</emphasis> takes on the values <emphasis role="bold">RED</emphasis>, <emphasis role="bold">GREEN</emphasis>, <emphasis role="bold">BLUE</emphasis>, and
<emphasis role="bold">ALPHA</emphasis>).
These parameters are set by <citerefentry><refentrytitle>glPixelTransfer</refentrytitle></citerefentry>.
</para>
</refsect1>
<refsect1 id="notes"><title>Notes</title>
<para>
<function>glCopyConvolutionFilter1D</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>
</refsect1>
<refsect1 id="errors"><title>Errors</title>
<para>
<constant>GL_INVALID_ENUM</constant> is generated if <parameter>target</parameter> is not
<constant>GL_CONVOLUTION_1D</constant>.
</para>
<para>
<constant>GL_INVALID_ENUM</constant> is generated if <parameter>internalformat</parameter> is not one of the
allowable values.
</para>
<para>
<constant>GL_INVALID_VALUE</constant> is generated if <parameter>width</parameter> is less than zero or greater
than the maximum supported value.
This value may be queried with <citerefentry><refentrytitle>glGetConvolutionParameter</refentrytitle></citerefentry>
using target <constant>GL_CONVOLUTION_1D</constant> and name
<constant>GL_MAX_CONVOLUTION_WIDTH</constant>.
</para>
<para>
<constant>GL_INVALID_OPERATION</constant> is generated if <function>glCopyConvolutionFilter1D</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>, <citerefentry><refentrytitle>glGetConvolutionFilter</refentrytitle></citerefentry>
</para>
</refsect1>
<refsect1 id="seealso"><title>See Also</title>
<para>
<citerefentry><refentrytitle>glConvolutionFilter1D</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glConvolutionParameter</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glPixelTransfer</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>