<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "xhtml1-transitional.dtd">
<!-- saved from url=(0013)about:internet -->
<?xml-stylesheet type="text/xsl" href="mathml.xsl"?><html xmlns="http://www.w3.org/1999/xhtml" xmlns:pref="http://www.w3.org/2002/Math/preference" pref:renderer="mathplayer-dl"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><link rel="stylesheet" type="text/css" href="opengl-man.css" /><title>glGetCompressedTexImage</title><meta name="generator" content="DocBook XSL Stylesheets V1.69.1" /></head><body><div class="refentry" lang="en" xml:lang="en"><a id="glGetCompressedTexImage"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>glGetCompressedTexImage — return a compressed texture image</p></div><div class="refsynopsisdiv"><h2>C Specification</h2><div class="funcsynopsis"><table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0"><tr><td><code class="funcdef">void <b class="fsfunc">glGetCompressedTexImage</b>(</code></td><td>GLenum  </td><td><var class="pdparam">target</var>, </td></tr><tr><td> </td><td>GLint  </td><td><var class="pdparam">lod</var>, </td></tr><tr><td> </td><td>GLvoid *  </td><td><var class="pdparam">img</var><code>)</code>;</td></tr></table></div></div><div class="refsect1" lang="en" xml:lang="en"><a id="parameters"></a><h2>Parameters</h2><div class="variablelist"><dl><dt><span class="term"><em class="parameter"><code>target</code></em></span></dt><dd><p>
                    Specifies which texture is to be obtained.
                    <code class="constant">GL_TEXTURE_1D</code>, <code class="constant">GL_TEXTURE_2D</code>, <code class="constant">GL_TEXTURE_3D</code>,
                    <code class="constant">GL_TEXTURE_CUBE_MAP_POSITIVE_X</code>,
                    <code class="constant">GL_TEXTURE_CUBE_MAP_NEGATIVE_X</code>,
                    <code class="constant">GL_TEXTURE_CUBE_MAP_POSITIVE_Y</code>,
                    <code class="constant">GL_TEXTURE_CUBE_MAP_NEGATIVE_Y</code>,
                    <code class="constant">GL_TEXTURE_CUBE_MAP_POSITIVE_Z</code>, and
                    <code class="constant">GL_TEXTURE_CUBE_MAP_NEGATIVE_Z</code>
                    are accepted.
                </p></dd><dt><span class="term"><em class="parameter"><code>lod</code></em></span></dt><dd><p>
                    Specifies the level-of-detail number of the desired image.
                    Level 0 is the base image level.
                    Level 
                    <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mi mathvariant="italic">n</mml:mi></mml:math>
                    is the 
                    <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mi mathvariant="italic">n</mml:mi></mml:math>th
                    mipmap reduction image.
                </p></dd><dt><span class="term"><em class="parameter"><code>img</code></em></span></dt><dd><p>
                    Returns the compressed texture image.
                </p></dd></dl></div></div><div class="refsect1" lang="en" xml:lang="en"><a id="description"></a><h2>Description</h2><p>
            <code class="function">glGetCompressedTexImage</code> returns the compressed texture image associated with <em class="parameter"><code>target</code></em> and <em class="parameter"><code>lod</code></em>
            into <em class="parameter"><code>img</code></em>.  <em class="parameter"><code>img</code></em> should be an array of
            <code class="constant">GL_TEXTURE_COMPRESSED_IMAGE_SIZE</code> bytes.
            <em class="parameter"><code>target</code></em> specifies whether the desired texture image was one specified by
            <a href="glTexImage1D.xml"><span class="citerefentry"><span class="refentrytitle">glTexImage1D</span></span></a> (<code class="constant">GL_TEXTURE_1D</code>),
            <a href="glTexImage2D.xml"><span class="citerefentry"><span class="refentrytitle">glTexImage2D</span></span></a> (<code class="constant">GL_TEXTURE_2D</code> or any of <code class="constant">GL_TEXTURE_CUBE_MAP_*</code>), or
            <a href="glTexImage3D.xml"><span class="citerefentry"><span class="refentrytitle">glTexImage3D</span></span></a> (<code class="constant">GL_TEXTURE_3D</code>).
            <em class="parameter"><code>lod</code></em> specifies the level-of-detail number of the desired image.
        </p><p>
            If a non-zero named buffer object is bound to the <code class="constant">GL_PIXEL_PACK_BUFFER</code> target 
            (see <a href="glBindBuffer.xml"><span class="citerefentry"><span class="refentrytitle">glBindBuffer</span></span></a>) while a texture image is
            requested, <em class="parameter"><code>img</code></em> is treated as a byte offset into the buffer object's data store.
        </p><p>
            To minimize errors, first verify that the texture is compressed by calling
            <a href="glGetTexLevelParameter.xml"><span class="citerefentry"><span class="refentrytitle">glGetTexLevelParameter</span></span></a> with argument <code class="constant">GL_TEXTURE_COMPRESSED</code>.  If
            the texture is compressed, then determine the amount of memory required to
            store the compressed texture by calling <a href="glGetTexLevelParameter.xml"><span class="citerefentry"><span class="refentrytitle">glGetTexLevelParameter</span></span></a> with
            argument <code class="constant">GL_TEXTURE_COMPRESSED_IMAGE_SIZE</code>.  Finally, retrieve the
            internal format of the texture by calling <a href="glGetTexLevelParameter.xml"><span class="citerefentry"><span class="refentrytitle">glGetTexLevelParameter</span></span></a> with
            argument <code class="constant">GL_TEXTURE_INTERNAL_FORMAT</code>.
            To store the texture for later use, associate the internal format and size
            with the retrieved texture image.  These data can be used by the respective
            texture or subtexture loading routine used for loading <em class="parameter"><code>target</code></em> textures.
        </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="errors"></a><h2>Errors</h2><p>
            <code class="constant">GL_INVALID_VALUE</code> is generated if <em class="parameter"><code>lod</code></em> is less than zero or greater
            than the maximum number of LODs permitted by the implementation.
        </p><p>
            <code class="constant">GL_INVALID_OPERATION</code> is generated if <code class="function">glGetCompressedTexImage</code> is used to retrieve a
            texture that is in an uncompressed internal format.
        </p><p>
            <code class="constant">GL_INVALID_OPERATION</code> is generated if a non-zero buffer object name is bound to the
            <code class="constant">GL_PIXEL_PACK_BUFFER</code> target and the buffer object's data store is currently mapped.
        </p><p>
            <code class="constant">GL_INVALID_OPERATION</code> is generated if a non-zero buffer object name is bound to the
            <code class="constant">GL_PIXEL_PACK_BUFFER</code> target and the data would be packed to the buffer 
            object such that the memory writes required would exceed the data store size.
        </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="associatedgets"></a><h2>Associated Gets</h2><p>
            <a href="glGetTexLevelParameter.xml"><span class="citerefentry"><span class="refentrytitle">glGetTexLevelParameter</span></span></a> with argument <code class="constant">GL_TEXTURE_COMPRESSED</code>
        </p><p>
            <a href="glGetTexLevelParameter.xml"><span class="citerefentry"><span class="refentrytitle">glGetTexLevelParameter</span></span></a> with argument <code class="constant">GL_TEXTURE_COMPRESSED_IMAGE_SIZE</code>
        </p><p>
            <a href="glGetTexLevelParameter.xml"><span class="citerefentry"><span class="refentrytitle">glGetTexLevelParameter</span></span></a> with argument <code class="constant">GL_TEXTURE_INTERNAL_FORMAT</code>
        </p><p>
            <a href="glGet.xml"><span class="citerefentry"><span class="refentrytitle">glGet</span></span></a> with argument <code class="constant">GL_PIXEL_PACK_BUFFER_BINDING</code>
        </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="seealso"></a><h2>See Also</h2><p>
            <a href="glActiveTexture.xml"><span class="citerefentry"><span class="refentrytitle">glActiveTexture</span></span></a>,
            <a href="glCompressedTexImage1D.xml"><span class="citerefentry"><span class="refentrytitle">glCompressedTexImage1D</span></span></a>,
            <a href="glCompressedTexImage2D.xml"><span class="citerefentry"><span class="refentrytitle">glCompressedTexImage2D</span></span></a>,
            <a href="glCompressedTexImage3D.xml"><span class="citerefentry"><span class="refentrytitle">glCompressedTexImage3D</span></span></a>,
            <a href="glCompressedTexSubImage1D.xml"><span class="citerefentry"><span class="refentrytitle">glCompressedTexSubImage1D</span></span></a>,
            <a href="glCompressedTexSubImage2D.xml"><span class="citerefentry"><span class="refentrytitle">glCompressedTexSubImage2D</span></span></a>,
            <a href="glCompressedTexSubImage3D.xml"><span class="citerefentry"><span class="refentrytitle">glCompressedTexSubImage3D</span></span></a>,
            <a href="glReadPixels.xml"><span class="citerefentry"><span class="refentrytitle">glReadPixels</span></span></a>,
            <a href="glTexImage1D.xml"><span class="citerefentry"><span class="refentrytitle">glTexImage1D</span></span></a>,
            <a href="glTexImage2D.xml"><span class="citerefentry"><span class="refentrytitle">glTexImage2D</span></span></a>,
            <a href="glTexImage3D.xml"><span class="citerefentry"><span class="refentrytitle">glTexImage3D</span></span></a>,
            <a href="glTexParameter.xml"><span class="citerefentry"><span class="refentrytitle">glTexParameter</span></span></a>,
            <a href="glTexSubImage1D.xml"><span class="citerefentry"><span class="refentrytitle">glTexSubImage1D</span></span></a>,
            <a href="glTexSubImage2D.xml"><span class="citerefentry"><span class="refentrytitle">glTexSubImage2D</span></span></a>,
            <a href="glTexSubImage3D.xml"><span class="citerefentry"><span class="refentrytitle">glTexSubImage3D</span></span></a>
        </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="Copyright"></a><h2>Copyright</h2><p>
            Copyright <span class="trademark"></span>© 1991-2006
            Silicon Graphics, Inc. This document is licensed under the SGI
            Free Software B License. For details, see
            <a href="http://oss.sgi.com/projects/FreeB/" target="_top">http://oss.sgi.com/projects/FreeB/</a>.
        </p></div></div></body></html>
