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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="glTexSubImage2D">
  <refmeta>
    <refentrytitle>glTexSubImage2D</refentrytitle>
    <manvolnum>3G</manvolnum>
  </refmeta>

  <refnamediv>
    <refname>glTexSubImage2D</refname>
    <refpurpose>specify a two-dimensional texture subimage</refpurpose>
  </refnamediv>

  <refsynopsisdiv>
    <title>C Specification</title>

    <funcsynopsis>
      <funcprototype>
        <funcdef>void <function>glTexSubImage2D</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>GLenum <parameter>type</parameter></paramdef>
        <paramdef>const GLvoid * <parameter>pixels</parameter></paramdef>
      </funcprototype>
    </funcsynopsis>
  </refsynopsisdiv>

  <refsect1>
    <title>Parameters</title>

    <variablelist>
      <varlistentry>
        <term>
          <parameter>target</parameter>
        </term>

        <listitem>
          <para>Specifies the target texture. Must be 
          <constant>GL_TEXTURE_2D</constant>.</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 <parameter>n</parameter> is the 
          <parameter>n</parameter>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 of the pixel data. The following
          symbolic values are accepted: 
          <constant>GL_ALPHA</constant>, 
          <constant>GL_RGB</constant>, 
          <constant>GL_RGBA</constant>, 
          <constant>GL_LUMINANCE</constant>, and 
          <constant>GL_LUMINANCE_ALPHA</constant>.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term>
          <parameter>type</parameter>
        </term>

        <listitem>
          <para>Specifies the data type of the pixel data. The
          following symbolic values are accepted: 
          <constant>GL_UNSIGNED_BYTE</constant>, 
          <constant>GL_UNSIGNED_SHORT_5_6_5</constant>, 
          <constant>GL_UNSIGNED_SHORT_4_4_4_4</constant>, and 
          <constant>GL_UNSIGNED_SHORT_5_5_5_1</constant>.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term>
          <parameter>pixels</parameter>
        </term>

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

  <refsect1>
    <title>Description</title>

    <para>Texturing maps a portion of a specified texture image
    onto each graphical primitive for which texturing is enabled.
    To enable and disable two-dimensional texturing, call 
    <citerefentry><refentrytitle>glEnable</refentrytitle></citerefentry> and 
    <citerefentry><refentrytitle>glDisable</refentrytitle></citerefentry>
    with argument <constant>GL_TEXTURE_2D</constant>.
    Two-dimensional texturing is initially disabled.
    </para>

    <para>
    <function>glTexSubImage2D</function>
    redefines a contiguous subregion of an existing two-dimensional
    texture image. The texels referenced by <parameter>pixels</parameter>
    replace the portion of the existing texture array with x indices 
    <parameter>xoffset</parameter> and 
    <inlineequation><math>
      <mi>xoffset</mi><mo>+</mo><mi>width</mi><mo>-</mo><mn>1</mn>
    </math></inlineequation>,
    inclusive, and y indices <parameter>yoffset</parameter> and 
    <inlineequation><math>
      <mi>yoffset</mi><mo>+</mo><mi>height</mi><mo>-</mo><mn>1</mn>
    </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 zero width or
    height, but such a specification has no effect.</para>
  </refsect1>

  <refsect1>
    <title>Notes</title>

    <para>
    <citerefentry><refentrytitle>glPixelStore</refentrytitle></citerefentry>
    affects texture images in exactly the way it affects
    <citerefentry><refentrytitle>glTexImage2D</refentrytitle></citerefentry>.
    </para>

    <para>
    <function>glTexSubImage2D</function>
    specifies a two-dimensional sub texture for the currently bound texture,
    specified with
    <citerefentry><refentrytitle>glBindTexture</refentrytitle></citerefentry>
    and current texture
    unit, specified with 
    <citerefentry><refentrytitle>glActiveTexture</refentrytitle></citerefentry>.
    </para>
  </refsect1>

  <refsect1>
    <title>Errors</title>

    <para><constant>GL_INVALID_ENUM</constant> is generated if 
    <parameter>target</parameter> is not <constant>GL_TEXTURE_2D</constant>.
    </para>

    <para><constant>GL_INVALID_OPERATION</constant> 
    is generated if the texture array has not been defined by a previous
    <citerefentry><refentrytitle>glTexImage2D</refentrytitle></citerefentry> or
    <citerefentry><refentrytitle>glCopyTexImage2D</refentrytitle></citerefentry>
    operation.</para>

    <para><constant>GL_INVALID_VALUE</constant> is generated if 
    <parameter>level</parameter> is less than 0.</para>

    <para><constant>GL_INVALID_VALUE</constant> may be generated if 
    <parameter>level</parameter> is greater than 
    <inlineequation><math>
      <msub><mo>log</mo><mn>2</mn></msub><mi>max</mi>
    </math></inlineequation>, where
    <replaceable>max</replaceable> is the returned value of
    <constant>GL_MAX_TEXTURE_SIZE</constant>.</para>

    <para><constant>GL_INVALID_VALUE</constant> is generated if
    <inlineequation><math>
      <mi>xoffset</mi><mo>&lt;</mo><mo>-</mo><mi>b</mi>
    </math></inlineequation>,
    <inlineequation><math>
      <mi>xoffset</mi><mo>+</mo><mi>width</mi><mo>&gt;</mo>
      <mfenced><mrow><mi>w</mi><mo>-</mo><mi>b</mi></mrow></mfenced>
    </math></inlineequation>,
    <inlineequation><math>
      <mi>yoffset</mi><mo>&lt;</mo><mo>-</mo><mi>b</mi>
    </math></inlineequation>, or
    <inlineequation><math>
      <mi>yoffset</mi><mo>+</mo><mi>height</mi><mo>&gt;</mo>
      <mfenced><mrow><mi>h</mi><mo>-</mo><mi>b</mi></mrow></mfenced>
    </math></inlineequation>, where
    <replaceable>w</replaceable> is the texture width,
    <replaceable>h</replaceable> is the texture height, and
    <replaceable>b</replaceable> is the border of the texture
    image being modified.
    Note that <replaceable>w</replaceable> and <replaceable>h</replaceable>
    include twice the border width.</para>

    <para><constant>GL_INVALID_VALUE</constant> is generated if 
    <parameter>width</parameter> or 
    <parameter>height</parameter> is less than 0.</para>

    <para><constant>GL_INVALID_ENUM</constant> is generated if 
    <parameter>format</parameter> is not an accepted constant.</para>

    <para><constant>GL_INVALID_ENUM</constant> is generated if 
    <parameter>type</parameter> is not a type constant.</para>

    <para><constant>GL_INVALID_OPERATION</constant> is generated if 
    <parameter>type</parameter> is 
    <constant>GL_UNSIGNED_SHORT_5_6_5</constant> and 
    <parameter>format</parameter> is not 
    <constant>GL_RGB</constant>.</para>

    <para><constant>GL_INVALID_OPERATION</constant> is generated if 
    <parameter>type</parameter> is one of 
    <constant>GL_UNSIGNED_SHORT_4_4_4_4</constant>, or 
    <constant>GL_UNSIGNED_SHORT_5_5_5_1</constant> and 
    <parameter>format</parameter> is not 
    <constant>GL_RGBA</constant>.</para>
  </refsect1>

  <refsect1>
    <title>Associated Gets</title>

    <para>
    <citerefentry><refentrytitle>glGetInteger</refentrytitle></citerefentry>
    with argument <constant>GL_MAX_TEXTURE_SIZE</constant></para>
  </refsect1>

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

    <para>
    <citerefentry><refentrytitle>glActiveTexture</refentrytitle></citerefentry>, 
    <citerefentry><refentrytitle>glBindTexture</refentrytitle></citerefentry>, 
    <citerefentry><refentrytitle>glCompressedTexSubImage2D</refentrytitle></citerefentry>, 
    <citerefentry><refentrytitle>glCopyTexSubImage2D</refentrytitle></citerefentry>, 
    <citerefentry><refentrytitle>glGetInteger</refentrytitle></citerefentry>, 
    <citerefentry><refentrytitle>glPixelStore</refentrytitle></citerefentry>, 
    <citerefentry><refentrytitle>glTexEnv</refentrytitle></citerefentry>, 
    <citerefentry><refentrytitle>glTexImage2D</refentrytitle></citerefentry>, 
    <citerefentry><refentrytitle>glTexParameter</refentrytitle></citerefentry>
    </para>
  </refsect1>
</refentry>