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<refentry xmlns="http://docbook.org/ns/docbook" version="5.0" xml:id="glCompressedTexSubImage2D">
    <info>
        <copyright>
            <year>1991-2006</year>
            <holder>Silicon Graphics, Inc.</holder>
        </copyright>
        <copyright>
            <year>2010-2014</year>
            <holder>Khronos Group</holder>
        </copyright>
    </info>
    <refmeta>
        <refentrytitle>glCompressedTexSubImage2D</refentrytitle>
        <manvolnum>3G</manvolnum>
    </refmeta>
    <refnamediv>
        <refname>glCompressedTexSubImage2D</refname>
        <refname>glCompressedTextureSubImage2D</refname>
        <refpurpose>specify a two-dimensional texture subimage in a compressed format</refpurpose>
    </refnamediv>
    <refsynopsisdiv><title>C Specification</title>
        <funcsynopsis>
            <funcprototype>
                <funcdef>void <function>glCompressedTexSubImage2D</function></funcdef>
                <paramdef>GLenum <parameter>target</parameter></paramdef>
                <paramdef>GLint <parameter>level</parameter></paramdef>
                <paramdef>GLint <parameter>xoffset</parameter></paramdef>
                <paramdef>GLint <parameter>yoffset</parameter></paramdef>
                <paramdef>GLsizei <parameter>width</parameter></paramdef>
                <paramdef>GLsizei <parameter>height</parameter></paramdef>
                <paramdef>GLenum <parameter>format</parameter></paramdef>
                <paramdef>GLsizei <parameter>imageSize</parameter></paramdef>
                <paramdef>const GLvoid * <parameter>data</parameter></paramdef>
            </funcprototype>
            <funcprototype>
                <funcdef>void <function>glCompressedTextureSubImage2D</function></funcdef>
                <paramdef>GLuint <parameter>texture</parameter></paramdef>
                <paramdef>GLint <parameter>level</parameter></paramdef>
                <paramdef>GLint <parameter>xoffset</parameter></paramdef>
                <paramdef>GLint <parameter>yoffset</parameter></paramdef>
                <paramdef>GLsizei <parameter>width</parameter></paramdef>
                <paramdef>GLsizei <parameter>height</parameter></paramdef>
                <paramdef>GLenum <parameter>format</parameter></paramdef>
                <paramdef>GLsizei <parameter>imageSize</parameter></paramdef>
                <paramdef>const void *<parameter>data</parameter></paramdef>
            </funcprototype>
        </funcsynopsis>
    </refsynopsisdiv>
    <refsect1 xml:id="parameters"><title>Parameters</title>
        <variablelist>
        <varlistentry>
            <term><parameter>target</parameter></term>

        <listitem>
          <para>Specifies the target to which the texture is bound for
          <function>glCompressedTexSubImage2D</function> function. Must be
          <constant>GL_TEXTURE_1D_ARRAY</constant>,
          <constant>GL_TEXTURE_2D</constant>,
          <constant>GL_TEXTURE_CUBE_MAP_POSITIVE_X</constant>,
          <constant>GL_TEXTURE_CUBE_MAP_NEGATIVE_X</constant>,
          <constant>GL_TEXTURE_CUBE_MAP_POSITIVE_Y</constant>,
          <constant>GL_TEXTURE_CUBE_MAP_NEGATIVE_Y</constant>,
          <constant>GL_TEXTURE_CUBE_MAP_POSITIVE_Z</constant>, or
          <constant>GL_TEXTURE_CUBE_MAP_NEGATIVE_Z</constant>.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><parameter>texture</parameter></term>

        <listitem>
          <para>Specifies the texture object name for
          <function>glCompressedTextureSubImage2D</function> function.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><parameter>level</parameter></term>

        <listitem>
          <para>Specifies the level-of-detail number. Level 0 is the base
          image level. Level <emphasis>n</emphasis> is the
          <emphasis>n</emphasis>th mipmap reduction image.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><parameter>xoffset</parameter></term>

        <listitem>
          <para>Specifies a texel offset in the x direction within the texture
          array.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><parameter>yoffset</parameter></term>

        <listitem>
          <para>Specifies a texel offset in the y direction within the texture
          array.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><parameter>width</parameter></term>

        <listitem>
          <para>Specifies the width of the texture subimage.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><parameter>height</parameter></term>

        <listitem>
          <para>Specifies the height of the texture subimage.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><parameter>format</parameter></term>

        <listitem>
          <para>Specifies the format of the compressed image data stored at
          address <parameter>data</parameter>.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><parameter>imageSize</parameter></term>

        <listitem>
          <para>Specifies the number of unsigned bytes of image data starting
          at the address specified by <parameter>data</parameter>.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><parameter>data</parameter></term>

        <listitem>
          <para>Specifies a pointer to the compressed image data in
          memory.</para>
        </listitem>
      </varlistentry>
    </variablelist>
  </refsect1>

  <refsect1 xml:id="description">
    <title>Description</title>

    <para>Texturing allows elements of an image array to be read by
    shaders.</para>

    <para><function>glCompressedTexSubImage2D</function> and
    <function>glCompressedTextureSubImage2D</function> redefine a contiguous
    subregion of an existing two-dimensional texture image. The texels
    referenced by <parameter>data</parameter> replace the portion of the
    existing texture array with x indices <parameter>xoffset</parameter> and
            <inlineequation><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
                <!-- eqn: xoffset  +  width  -  1: -->
                <mml:mrow>
                    <mml:mi mathvariant="italic">xoffset</mml:mi>
                    <mml:mo>+</mml:mo>
                    <mml:mi mathvariant="italic">width</mml:mi>
                    <mml:mo>-</mml:mo>
                    <mml:mn>1</mml:mn>
                </mml:mrow>
            </mml:math></inlineequation>,
            and the y indices <parameter>yoffset</parameter> and
            <inlineequation><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
                <!-- eqn: yoffset  +  height  -  1: -->
                <mml:mrow>
                    <mml:mi mathvariant="italic">yoffset</mml:mi>
                    <mml:mo>+</mml:mo>
                    <mml:mi mathvariant="italic">height</mml:mi>
                    <mml:mo>-</mml:mo>
                    <mml:mn>1</mml:mn>
                </mml:mrow>
            </mml:math></inlineequation>,
            inclusive.
            This region may not include any texels
    outside the range of the texture array as it was originally specified. It
    is not an error to specify a subtexture with width of 0, but such a
    specification has no effect.</para>

    <para><parameter>internalformat</parameter> must be a known compressed
    image format (such as <constant>GL_RGTC</constant>) or an
    extension-specified compressed-texture format. The
    <parameter>format</parameter> of the compressed texture image is selected
    by the GL implementation that compressed it (see
    <citerefentry><refentrytitle>glTexImage2D</refentrytitle></citerefentry>)
    and should be queried at the time the texture was
    compressed with
    <citerefentry><refentrytitle>glGetTexLevelParameter</refentrytitle></citerefentry>.</para>

    <para>If a non-zero named buffer object is bound to the
    <constant>GL_PIXEL_UNPACK_BUFFER</constant> target (see
    <citerefentry><refentrytitle>glBindBuffer</refentrytitle></citerefentry>)
    while a texture image is specified,
    <parameter>data</parameter> is treated as a byte offset into the buffer
    object's data store.</para>
  </refsect1>

  <refsect1 xml:id="errors">
    <title>Errors</title>

    <para><constant>GL_INVALID_ENUM</constant> is generated if
    <parameter>internalformat</parameter> is of the generic compressed
    internal formats: <constant>GL_COMPRESSED_RED</constant>,
    <constant>GL_COMPRESSED_RG</constant>,
    <constant>GL_COMPRESSED_RGB</constant>,
    <constant>GL_COMPRESSED_RGBA</constant>.
    <constant>GL_COMPRESSED_SRGB</constant>, or
    <constant>GL_COMPRESSED_SRGB_ALPHA</constant>.</para>

    <para><constant>GL_INVALID_ENUM</constant> is generated by
    <function>glCompressedTexSubImage2D</function> if
    <parameter>target</parameter> is <constant>GL_TEXTURE_RECTANGLE</constant>
    or <constant>GL_PROXY_TEXTURE_RECTANGLE</constant>.</para>

    <para><constant>GL_INVALID_VALUE</constant> is generated if
    <parameter>imageSize</parameter> is not consistent with the format,
    dimensions, and contents of the specified compressed image data.</para>

    <para><constant>GL_INVALID_OPERATION</constant> is generated if parameter
    combinations are not supported by the specific compressed internal format
    as specified in the specific texture compression extension.</para>

    <para><constant>GL_INVALID_OPERATION</constant> is generated if a non-zero
    buffer object name is bound to the
    <constant>GL_PIXEL_UNPACK_BUFFER</constant> target and the buffer object's
    data store is currently mapped.</para>

    <para><constant>GL_INVALID_OPERATION</constant> is generated if a non-zero
    buffer object name is bound to the
    <constant>GL_PIXEL_UNPACK_BUFFER</constant> target and the data would be
    unpacked from the buffer object such that the memory reads required would
    exceed the data store size.</para>

    <para><constant>GL_INVALID_OPERATION</constant> is generated by
    <function>glCompressedTextureSubImage2D</function> if
    <parameter>texture</parameter> is not the name of an existing texture
    object.</para>

    <para><constant>GL_INVALID_OPERATION</constant> is generated by
    <function>glCompressedTextureSubImage2D</function> if the effective target
    is <constant>GL_TEXTURE_RECTANGLE</constant>.</para>

    <para>Undefined results, including abnormal program termination, are
    generated if <parameter>data</parameter> is not encoded in a manner
    consistent with the extension specification defining the internal
    compression format.</para>
    </refsect1>
    <refsect1 xml:id="associatedgets"><title>Associated Gets</title>
        <para>
            <citerefentry><refentrytitle>glGetCompressedTexImage</refentrytitle></citerefentry>
        </para>
        <para>
            <citerefentry><refentrytitle>glGet</refentrytitle></citerefentry> with argument <constant>GL_TEXTURE_COMPRESSED</constant>
        </para>
        <para>
            <citerefentry><refentrytitle>glGet</refentrytitle></citerefentry> with argument <constant>GL_PIXEL_UNPACK_BUFFER_BINDING</constant>
        </para>
        <para>
            <citerefentry><refentrytitle>glGetTexLevelParameter</refentrytitle></citerefentry> with arguments <constant>GL_TEXTURE_INTERNAL_FORMAT</constant>
            and <constant>GL_TEXTURE_COMPRESSED_IMAGE_SIZE</constant>
        </para>
    </refsect1>
    <refsect1 xml:id="versions"><title>Version Support</title>
        <informaltable>
            <tgroup cols="13" align="left">
                <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="apifunchead.xml" xpointer="xpointer(/*/*)"/>
                <tbody>
                    <row>
                        <entry><function>glCompressedTexSubImage2D</function></entry>
                        <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="apiversion.xml" xpointer="xpointer(/*/*[@role='20']/*)"/>
                    </row>
                    <row>
                        <entry><function>glCompressedTextureSubImage2D</function></entry>
                        <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="apiversion.xml" xpointer="xpointer(/*/*[@role='45']/*)"/>
                    </row>
                </tbody>
            </tgroup>
        </informaltable>
    </refsect1>
    <refsect1 xml:id="seealso"><title>See Also</title>
        <para>
            <citerefentry><refentrytitle>glActiveTexture</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glCompressedTexImage1D</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glCompressedTexImage2D</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glCompressedTexImage3D</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glCompressedTexSubImage1D</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glCompressedTexSubImage3D</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glCopyTexImage1D</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glCopyTexImage2D</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glCopyTexSubImage1D</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glCopyTexSubImage2D</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glCopyTexSubImage3D</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glPixelStore</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glTexImage2D</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glTexImage3D</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glTexSubImage1D</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glTexSubImage2D</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glTexSubImage3D</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glTexParameter</refentrytitle></citerefentry>
        </para>
    </refsect1>
    <refsect1 xml:id="Copyright"><title>Copyright</title>
        <para>
            Copyright <trademark class="copyright"/> 1991-2006 Silicon Graphics, Inc.
            Copyright <trademark class="copyright"/> 2010-2014 Khronos Group.
            This document is licensed under the SGI Free Software B License.
            For details, see
            <link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://oss.sgi.com/projects/FreeB/">http://oss.sgi.com/projects/FreeB/</link>.
        </para>
    </refsect1>
</refentry>
