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<refentry id="glPixelStorei">
    <refmeta>
        <refmetainfo>
            <copyright>
                <year>1991-2006</year>
                <holder>Silicon Graphics, Inc.</holder>
            </copyright>
        </refmetainfo>
        <refentrytitle>glPixelStorei</refentrytitle>
        <manvolnum>3G</manvolnum>
    </refmeta>
    <refnamediv>
        <refname>glPixelStorei</refname>
        <refpurpose>set pixel storage modes</refpurpose>
    </refnamediv>
    <refsynopsisdiv><title>C Specification</title>
        <funcsynopsis>
            <funcprototype>
                <funcdef>void <function>glPixelStorei</function></funcdef>
                <paramdef>GLenum <parameter>pname</parameter></paramdef>
                <paramdef>GLint <parameter>param</parameter></paramdef>
            </funcprototype>
        </funcsynopsis>
    </refsynopsisdiv>
    <!-- eqn: ignoring delim $$ -->
    <refsect1 id="parameters"><title>Parameters</title>
        <variablelist>
        <varlistentry>
            <term><parameter>pname</parameter></term>
            <listitem>
                <para>
                    Specifies the symbolic name of the parameter to be set.
                    One value affects the packing of pixel data into memory:
                    <constant>GL_PACK_ALIGNMENT</constant>.
                    The other affects the unpacking of pixel data <emphasis>from</emphasis> memory:
                    <constant>GL_UNPACK_ALIGNMENT</constant>.
                </para>
            </listitem>
        </varlistentry>
        <varlistentry>
            <term><parameter>param</parameter></term>
            <listitem>
                <para>
                    Specifies the value that <parameter>pname</parameter> is set to.
                </para>
            </listitem>
        </varlistentry>
        </variablelist>
    </refsect1>
    <refsect1 id="description"><title>Description</title>
        <para>
            <function>glPixelStorei</function> sets pixel storage modes that affect the operation of subsequent
            <citerefentry><refentrytitle>glReadPixels</refentrytitle></citerefentry> as well as the unpacking of
            texture patterns (see <citerefentry><refentrytitle>glTexImage2D</refentrytitle></citerefentry> and
            <citerefentry><refentrytitle>glTexSubImage2D</refentrytitle></citerefentry>).
        </para>
        <para>
            <parameter>pname</parameter> is a symbolic constant indicating the parameter to be set, and
            <parameter>param</parameter> is the new value.  One storage parameter affects
            how pixel data is returned to client memory:
        </para>
        <variablelist>
            <varlistentry>
                <term><constant>GL_PACK_ALIGNMENT</constant></term>
                <listitem>
                    <para>
                        Specifies the alignment requirements for the start of each pixel row in memory.
                        The allowable values are
                        1 (byte-alignment),
                        2 (rows aligned to even-numbered bytes),
                        4 (word-alignment), and
                        8 (rows start on double-word boundaries).
                    </para>
                </listitem>
            </varlistentry>
        </variablelist>
        <para>
            The other storage parameter affects how pixel data is
            read from client memory:
        </para>
        <variablelist>
            <varlistentry>
                <term><constant>GL_UNPACK_ALIGNMENT</constant></term>
                <listitem>
                    <para>
                        Specifies the alignment requirements for the start of each pixel row in memory.
                        The allowable values are
                        1 (byte-alignment),
                        2 (rows aligned to even-numbered bytes),
                        4 (word-alignment), and
                        8 (rows start on double-word boundaries).
                    </para>
                </listitem>
            </varlistentry>
        </variablelist>
        <para>
            The following table gives the type,
            initial value,
            and range of valid values for each storage parameter
            that can be set with <function>glPixelStorei</function>.
        </para>
        <para>
        </para>
        <informaltable frame="topbot">
            <tgroup cols="4" align="left">
                <colspec/>
                <colspec align="center"/>
                <colspec align="center"/>
                <colspec align="center"/>
                <thead>
                    <row>
                        <entry rowsep="1" align="left"><emphasis role="bold">
                        <parameter>pname</parameter>
                        </emphasis></entry>
                        <entry rowsep="1" align="center"><emphasis role="bold">
                        Type
                        </emphasis></entry>
                        <entry rowsep="1" align="center"><emphasis role="bold">
                        Initial Value
                        </emphasis></entry>
                        <entry rowsep="1" align="center"><emphasis role="bold">
                        Valid Range
                        </emphasis></entry>
                    </row>
                </thead>
                <tbody>
                    <row>
                        <entry align="left">
                        <constant>GL_PACK_ALIGNMENT</constant>
                        </entry>
                        <entry align="center">
                        integer
                        </entry>
                        <entry align="center">
                        4
                        </entry>
                        <entry align="center">
                        1, 2, 4, or 8
                        </entry>
                    </row>
                    <row>
                        <entry align="left">
                        <constant>GL_UNPACK_ALIGNMENT</constant>
                        </entry>
                        <entry align="center">
                        integer
                        </entry>
                        <entry align="center">
                        4
                        </entry>
                        <entry align="center">
                        1, 2, 4, or 8
                        </entry>
                    </row>
                </tbody>
            </tgroup>
        </informaltable>
        <para>
            Boolean parameters are set to false if <parameter>param</parameter> is 0 and true otherwise.
        </para>
    </refsect1>
    <refsect1 id="errors"><title>Errors</title>
        <para>
            <constant>GL_INVALID_ENUM</constant> is generated if <parameter>pname</parameter> is not an accepted value.
        </para>
        <para>
            <constant>GL_INVALID_VALUE</constant> is generated if alignment is specified as other than 1, 2, 4, or 8.
        </para>
    </refsect1>
    <refsect1 id="associatedgets"><title>Associated Gets</title>
        <para>
            <citerefentry><refentrytitle>glGet</refentrytitle></citerefentry> with argument 
            <constant>GL_PACK_ALIGNMENT</constant> or <constant>GL_UNPACK_ALIGNMENT</constant>
        </para>
    </refsect1>
    <refsect1 id="seealso"><title>See Also</title>
        <para>
            <citerefentry><refentrytitle>glReadPixels</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glTexImage2D</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glTexSubImage2D</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>
