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OpenGL ES 1.0 and EGL 1.0 reference manual and man pages (written by
Claude Knaus, based on OpenGL SI man pages).

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook V4.2//EN" "DTD/docbook/docbookx.dtd">

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<refentry id="glPixelStore">
  <refmeta>
    <refentrytitle>glPixelStore</refentrytitle>
    <manvolnum>3G</manvolnum>
  </refmeta>

  <refnamediv>
    <refdescriptor>glPixelStore</refdescriptor>
    <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>

  <refsect1>
    <title>Parameters</title>

    <variablelist>
      <varlistentry>
        <term>
          <parameter>pname</parameter>
        </term>

        <listitem>
          <para>Specifies the symbolic name of the parameter to be set. 
          <constant>GL_PACK_ALIGNMENT</constant>
          affects the packing of pixel data into memory. 
          <constant>GL_UNPACK_ALIGNMENT</constant>
          affects the unpacking of pixel data 
          <parameter>from</parameter> memory.</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>
    <title>Description</title>

    <para> <function>glPixelStore</function>
    sets pixel storage modes that affect the operation of
    subsequent 
    <citerefentry><refentrytitle>glReadPixels</refentrytitle></citerefentry>
    as well as the unpacking of 
    <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. The following storage parameter affects how
    pixel data is returned to client memory. This value is
    significant for 
    <citerefentry><refentrytitle>glReadPixels</refentrytitle></citerefentry>:
    </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). The initial value is 4.</para>
        </listitem>
      </varlistentry>
    </variablelist>

    <para>The following storage parameter affects how pixel data is
    read from client memory. This value is significant for 
    <citerefentry><refentrytitle>glTexImage2D</refentrytitle></citerefentry>
    and 
    <citerefentry><refentrytitle>glTexSubImage2D</refentrytitle></citerefentry>:
    </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). The initial value is 4.</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>glPixelStore</function>.
    </para>

    <informaltable frame="none">
      <tgroup cols="4" align="center">
        <colspec />
        <colspec align="left"/>
        <colspec align="center"/>
        <colspec align="center"/>
        <colspec align="center"/>

        <thead>
          <row>
            <entry><parameter>pname</parameter></entry>
            <entry>Type</entry>
            <entry>Initial Value</entry>
            <entry>Valid Range</entry>
          </row>
        </thead>

        <tbody>
          <row>
            <entry><constant>GL_PACK_ALIGNMENT</constant></entry>
            <entry>integer</entry>
            <entry>4</entry>
            <entry>1, 2, 4, or 8</entry>
          </row>

          <row>
            <entry><constant>GL_UNPACK_ALIGNMENT</constant></entry>
            <entry>integer</entry>
            <entry>4</entry>
            <entry>1, 2, 4, or 8</entry>
          </row>
        </tbody>
      </tgroup>
    </informaltable>
-->
  </refsect1>

  <refsect1>
    <title>Notes</title>

    <para>Pixel storage modes are client states.</para>

    <para>
    <citerefentry><refentrytitle>glCompressedTexImage2D</refentrytitle></citerefentry>
    and 
    <citerefentry><refentrytitle>glCompressedTexSubImage2D</refentrytitle></citerefentry>
    are not affected by <function>glPixelStore</function>.
    </para>
  </refsect1>

  <refsect1>
    <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>
    <title>See Also</title>

    <para>
    <citerefentry><refentrytitle>glReadPixels</refentrytitle></citerefentry>, 
    <citerefentry><refentrytitle>glCompressedTexImage2D</refentrytitle></citerefentry>, 
    <citerefentry><refentrytitle>glCompressedTexSubImage2D</refentrytitle></citerefentry>, 
    <citerefentry><refentrytitle>glTexImage2D</refentrytitle></citerefentry>, 
    <citerefentry><refentrytitle>glTexSubImage2D</refentrytitle></citerefentry>
    </para>
  </refsect1>
</refentry>