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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="glCopyTexSubImage2D">
  <refmeta>
    <refentrytitle>glCopyTexSubImage2D</refentrytitle>
    <manvolnum>3G</manvolnum>
  </refmeta>

  <refnamediv>
    <refname>glCopyTexSubImage2D</refname>
    <refpurpose>specify a two-dimensional texture subimage with pixels from the color buffer</refpurpose>
  </refnamediv>

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

    <funcsynopsis>
      <funcprototype>
        <funcdef>void <function>glCopyTexSubImage2D</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>GLint <parameter>x</parameter></paramdef>
        <paramdef>GLint <parameter>y</parameter></paramdef>
        <paramdef>GLsizei <parameter>width</parameter></paramdef>
        <paramdef>GLsizei <parameter>height</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>x</parameter>, <parameter>y</parameter>
        </term>

        <listitem>
          <para>Specify the window coordinates of the lower left
          corner of the rectangular region of pixels to be
          copied.</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>
    </variablelist>
  </refsect1>

  <refsect1>
    <title>Description</title>

    <para><function>glCopyTexSubImage2D</function>
    replaces a rectangular portion of a two-dimensional texture
    image with pixels from the color buffer.
    </para>

    <para>The screen-aligned pixel rectangle with lower left corner at (
    <parameter>x</parameter>, <parameter>y</parameter>) and with width 
    <parameter>width</parameter> and height 
    <parameter>height</parameter>
    replaces the portion of the texture array with x indices 
    <parameter>xoffset</parameter> through 
    <inlineequation><math>
      <mi>xoffset</mi><mo>+</mo><mi>width</mi><mo>-</mo><mn>1</mn>
    </math></inlineequation>,
    inclusive, and y indices 
    <parameter>yoffset</parameter> through 
    <inlineequation><math>
      <mi>yoffset</mi><mo>+</mo><mi>height</mi><mo>-</mo><mn>1</mn>
    </math></inlineequation>,
    inclusive, at the mipmap level specified by 
    <parameter>level</parameter>.</para>

    <para>The pixels in the rectangle are processed the same way
    as with
    <citerefentry><refentrytitle>glCopyTexImage2D</refentrytitle></citerefentry>.
    </para>

    <para><function>glCopyTexSubImage2D</function> requires
    that the internal format of the currently bound texture is such that
    color buffer components can be dropped during conversion to the
    internal format, but new components cannot be added. For example,
    an <constant>RGB</constant> color buffer can be used to create
    <constant>LUMINANCE</constant> or <constant>RGB</constant>
    textures, but not <constant>ALPHA</constant>,
    <constant>LUMINANCE_ALPHA</constant> or <constant>RGBA</constant>
    textures.</para>

    <para>The destination rectangle in the texture array may not
    include any texels outside 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>

    <para>If any of the pixels within the specified rectangle of
    the current color buffer are outside the read window associated
    with the current rendering context, then the values obtained
    for those pixels are undefined.</para>

    <para>No change is made to the 
    <parameter>internalformat</parameter>,
    <parameter>width</parameter>, 
    <parameter>height</parameter>, or 
    <parameter>border</parameter> 
    parameters of the specified texture array or to texel values
    outside the specified subregion.</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 or if the internal format of the currently bound texture
    is not compatible with the color buffer format.</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>x</mi><mo>&lt;</mo><mo>-</mo><mi>b</mi>
    </math></inlineequation>, or

    <inlineequation><math>
      <mi>y</mi><mo>&lt;</mo><mo>-</mo><mi>b</mi>
    </math></inlineequation>, where
    <replaceable>b</replaceable> is the border
    of the texture being modified.</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>
  </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>glCompressedTexSubImage2D</refentrytitle></citerefentry>, 
    <citerefentry><refentrytitle>glCopyTexImage2D</refentrytitle></citerefentry>, 
    <citerefentry><refentrytitle>glGetInteger</refentrytitle></citerefentry>, 
    <citerefentry><refentrytitle>glTexEnv</refentrytitle></citerefentry>, 
    <citerefentry><refentrytitle>glTexImage2D</refentrytitle></citerefentry>, 
    <citerefentry><refentrytitle>glTexParameter</refentrytitle></citerefentry>, 
    <citerefentry><refentrytitle>glTexSubImage2D</refentrytitle></citerefentry>
    </para>
  </refsect1>
</refentry>