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< !DOCTYPE book PUBLIC "-//OASIS//DTD DocBook MathML Module V1.1b1//EN"
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<refentry id= "glCompressedTexImage2D" >
<refmeta >
<refmetainfo >
<copyright >
<year > 1991-2006</year>
<holder > Silicon Graphics, Inc.</holder>
</copyright>
</refmetainfo>
<refentrytitle > glCompressedTexImage2D</refentrytitle>
<manvolnum > 3G</manvolnum>
</refmeta>
<refnamediv >
<refname > glCompressedTexImage2D</refname>
<refpurpose > specify a two-dimensional texture image in a compressed format</refpurpose>
</refnamediv>
<refsynopsisdiv > <title > C Specification</title>
<funcsynopsis >
<funcprototype >
<funcdef > void <function > glCompressedTexImage2D</function> </funcdef>
<paramdef > GLenum <parameter > target</parameter> </paramdef>
<paramdef > GLint <parameter > level</parameter> </paramdef>
<paramdef > GLenum <parameter > internalformat</parameter> </paramdef>
<paramdef > GLsizei <parameter > width</parameter> </paramdef>
<paramdef > GLsizei <parameter > height</parameter> </paramdef>
<paramdef > GLint <parameter > border</parameter> </paramdef>
<paramdef > GLsizei <parameter > imageSize</parameter> </paramdef>
<paramdef > const GLvoid * <parameter > data</parameter> </paramdef>
</funcprototype>
</funcsynopsis>
</refsynopsisdiv>
<!-- eqn: ignoring delim $$ -->
<refsect1 id= "parameters" > <title > Parameters</title>
<variablelist >
<varlistentry >
<term > <parameter > target</parameter> </term>
<listitem >
<para >
Specifies the target texture.
Must be <constant > GL_TEXTURE_2D</constant> , <constant > GL_PROXY_TEXTURE_2D</constant> ,
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<constant > GL_TEXTURE_1D_ARRAY</constant> , <constant > GL_PROXY_TEXTURE_1D_ARRAY</constant> ,
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<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> ,
<constant > GL_TEXTURE_CUBE_MAP_NEGATIVE_Z</constant> , or
<constant > GL_PROXY_TEXTURE_CUBE_MAP</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 <emphasis > n</emphasis> is the <emphasis > n</emphasis> th mipmap reduction image.
</para>
</listitem>
</varlistentry>
<varlistentry >
<term > <parameter > internalformat</parameter> </term>
<listitem >
<para >
Specifies the format of the compressed image data stored at address <parameter > data</parameter> .
</para>
</listitem>
</varlistentry>
<varlistentry >
<term > <parameter > width</parameter> </term>
<listitem >
<para >
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Specifies the width of the texture image.
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All implementations support 2D texture and cube map texture images that are at least 16384 texels wide.
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</para>
</listitem>
</varlistentry>
<varlistentry >
<term > <parameter > height</parameter> </term>
<listitem >
<para >
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Specifies the height of the texture image.
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All implementations support 2D texture and cube map texture images that are at least 16384 texels high.
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</para>
</listitem>
</varlistentry>
<varlistentry >
<term > <parameter > border</parameter> </term>
<listitem >
<para >
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This value must be 0.
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</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 id= "description" > <title > Description</title>
<para >
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Texturing allows elements of an image array to be read by shaders.
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</para>
<para >
<function > glCompressedTexImage2D</function> loads a previously defined, and retrieved, compressed two-dimensional
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texture image if <parameter > target</parameter> is <constant > GL_TEXTURE_2D</constant> , or one of the
cube map faces such as <constant > GL_TEXTURE_CUBE_MAP_POSITIVE_X</constant> .
(see <citerefentry > <refentrytitle > glTexImage2D</refentrytitle> </citerefentry> ).
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</para>
<para >
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If <parameter > target</parameter> is <constant > GL_TEXTURE_1D_ARRAY</constant> , <parameter > data</parameter>
is treated as an array of compressed 1D textures.
</para>
<para >
If <parameter > target</parameter> is <constant > GL_PROXY_TEXTURE_2D</constant> , <constant > GL_PROXY_TEXTURE_1D_ARRAY</constant>
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or <constant > GL_PROXY_TEXTURE_CUBE_MAP</constant> , no data is read from <parameter > data</parameter> , but
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all of the texture image state is recalculated, checked for consistency,
and checked against the implementation's capabilities. If the
implementation cannot handle a texture of the requested texture size, it
sets all of the image state to 0, but does not generate an error (see
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<citerefentry > <refentrytitle > glGetError</refentrytitle> </citerefentry> ). To query for an entire mipmap array,
use an image array level greater than or equal to 1.
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</para>
<para >
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<parameter > internalformat</parameter> must be a known compressed image format (such as <constant > GL_RGTC</constant> )
or an extension-specified compressed-texture format.
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When a texture is loaded with <citerefentry > <refentrytitle > glTexImage2D</refentrytitle> </citerefentry> using a generic compressed
texture format (e.g., <constant > GL_COMPRESSED_RGB</constant> ), the GL selects from one of
its extensions supporting compressed textures. In order to load the
compressed texture image using <function > glCompressedTexImage2D</function> , query the compressed texture image's
size and format using <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>
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<para >
If the compressed data are arranged into fixed-size blocks of texels, the pixel
storage modes can be used to select a sub-rectangle from a larger containing rectangle.
These pixel storage modes operate in the same way as they do for <citerefentry > <refentrytitle > glTexImage2D</refentrytitle> </citerefentry> .
In the following description, denote by <mml:math > <mml:mrow > <mml:msub > <mml:mi > b</mml:mi> <mml:mi > s</mml:mi> </mml:msub> </mml:mrow> </mml:math> ,
<mml:math > <mml:mrow > <mml:msub > <mml:mi > b</mml:mi> <mml:mi > w</mml:mi> </mml:msub> </mml:mrow> </mml:math> ,
<mml:math > <mml:mrow > <mml:msub > <mml:mi > b</mml:mi> <mml:mi > h</mml:mi> </mml:msub> </mml:mrow> </mml:math> , and
<mml:math > <mml:mrow > <mml:msub > <mml:mi > b</mml:mi> <mml:mi > d</mml:mi> </mml:msub> </mml:mrow> </mml:math> ,
the values of pixel storage modes <constant > GL_UNPACK_COMPRESSED_BLOCK_SIZE</constant> ,
<constant > GL_UNPACK_COMPRESSED_BLOCK_WIDTH</constant> , <constant > GL_UNPACK_COMPRESSED_BLOCK_HEIGHT</constant> ,
and <constant > GL_UNPACK_COMPRESSED_BLOCK_DEPTH</constant> , respectively.
<mml:math > <mml:mrow > <mml:msub > <mml:mi > b</mml:mi> <mml:mi > s</mml:mi> </mml:msub> </mml:mrow> </mml:math> is
the compressed block size in bytes; <mml:math > <mml:mrow > <mml:msub > <mml:mi > b</mml:mi> <mml:mi > w</mml:mi> </mml:msub> </mml:mrow> </mml:math> ,
<mml:math > <mml:mrow > <mml:msub > <mml:mi > b</mml:mi> <mml:mi > h</mml:mi> </mml:msub> </mml:mrow> </mml:math> ,
and <mml:math > <mml:mrow > <mml:msub > <mml:mi > b</mml:mi> <mml:mi > d</mml:mi> </mml:msub> </mml:mrow> </mml:math> are the compressed block width, height, and depth in pixels.
</para>
<para >
By default the pixel storage modes <constant > GL_UNPACK_ROW_LENGTH</constant> ,
<constant > GL_UNPACK_SKIP_ROWS</constant> , <constant > GL_UNPACK_SKIP_PIXELS</constant> ,
<constant > GL_UNPACK_IMAGE_HEIGHT</constant> and <constant > GL_UNPACK_SKIP_IMAGES</constant>
are ignored for compressed images. To enable <constant > GL_UNPACK_SKIP_PIXELS</constant>
and <constant > GL_UNPACK_ROW_LENGTH</constant> , <mml:math > <mml:mrow > <mml:msub > <mml:mi > b</mml:mi> <mml:mi > s</mml:mi> </mml:msub> </mml:mrow> </mml:math>
and <mml:math > <mml:mrow > <mml:msub > <mml:mi > b</mml:mi> <mml:mi > w</mml:mi> </mml:msub> </mml:mrow> </mml:math> must both be non-zero.
To also enable <constant > GL_UNPACK_SKIP_ROWS</constant> and <constant > GL_UNPACK_IMAGE_HEIGHT</constant> ,
<mml:math > <mml:mrow > <mml:msub > <mml:mi > b</mml:mi> <mml:mi > h</mml:mi> </mml:msub> </mml:mrow> </mml:math> must be non-zero.
To also enable <constant > GL_UNPACK_SKIP_IMAGES</constant> , <mml:math > <mml:mrow > <mml:msub > <mml:mi > b</mml:mi> <mml:mi > d</mml:mi> </mml:msub> </mml:mrow> </mml:math>
must be non-zero. All parameters must be consistent with the compressed format to produce the desired results.
</para>
<para >
When selecting a sub-rectangle from a compressed image:
<itemizedlist >
<listitem > the value of <constant > GL_UNPACK_SKIP_PIXELS</constant> must be a multiple of <mml:math > <mml:mrow > <mml:msub > <mml:mi > b</mml:mi> <mml:mi > w</mml:mi> </mml:msub> </mml:mrow> </mml:math> ;</listitem>
<listitem > the value of <constant > GL_UNPACK_SKIP_ROWS</constant> must be a multiple of <mml:math > <mml:mrow > <mml:msub > <mml:mi > b</mml:mi> <mml:mi > w</mml:mi> </mml:msub> </mml:mrow> </mml:math> .</listitem>
</itemizedlist>
</para>
<para >
<parameter > imageSize</parameter> must be equal to:
</para>
<para >
<mml:math display = 'block' >
<mml:mrow >
<mml:msub >
<mml:mi > b</mml:mi>
<mml:mi > s</mml:mi>
</mml:msub>
<mml:mo lspace= '2px' rspace= '2px' > × </mml:mo>
<mml:mfenced open = '⌈' close = '⌉' >
<mml:mfrac >
<mml:mi > width</mml:mi>
<mml:msub >
<mml:mi > b</mml:mi>
<mml:mi > w</mml:mi>
</mml:msub>
</mml:mfrac>
</mml:mfenced>
<mml:mo lspace= '2px' rspace= '2px' > × </mml:mo>
<mml:mfenced open = '⌈' close = '⌉' >
<mml:mfrac >
<mml:mi > height</mml:mi>
<mml:msub >
<mml:mi > b</mml:mi>
<mml:mi > h</mml:mi>
</mml:msub>
</mml:mfrac>
</mml:mfenced>
</mml:mrow>
</mml:math>
</para>
</refsect1>
<refsect1 id= "notes" > <title > Notes</title>
<para >
The specific compressed internal formats <constant > GL_COMPRESSED_RGB8_ETC2</constant> ,
<constant > GL_COMPRESSED_SRGB8_ETC2</constant> ,
<constant > GL_COMPRESSED_RGB8_PUNCHTHROUGH_ALPHA1_ETC2</constant> ,
<constant > GL_COMPRESSED_SRGB8_PUNCHTHROUGH_ALPHA1_ETC2</constant> ,
<constant > GL_COMPRESSED_RGBA8_ETC2_EAC</constant> ,
<constant > GL_COMPRESSED_SRGB8_ALPHA8_ETC2_EAC</constant> ,
<constant > GL_COMPRESSED_R11_EAC</constant> ,
<constant > GL_COMPRESSED_SIGNED_R11_EAC</constant> ,
<constant > GL_COMPRESSED_RG11_EAC</constant> , and
<constant > GL_COMPRESSED_SIGNED_RG11_EAC</constant> are available only if the GL version
is 4.3 or higher.
</para>
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</refsect1>
<refsect1 id= "errors" > <title > Errors</title>
<para >
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<constant > GL_INVALID_ENUM</constant> is generated if <parameter > internalformat</parameter> is not one of the specific
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compressed internal formats:
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<constant > GL_COMPRESSED_RED_RGTC1</constant> ,
<constant > GL_COMPRESSED_SIGNED_RED_RGTC1</constant> ,
<constant > GL_COMPRESSED_RG_RGTC2</constant> ,
<constant > GL_COMPRESSED_SIGNED_RG_RGTC2</constant> .
<constant > GL_COMPRESSED_RGBA_BPTC_UNORM</constant> ,
<constant > GL_COMPRESSED_SRGB_ALPHA_BPTC_UNORM</constant> ,
<constant > GL_COMPRESSED_RGB_BPTC_SIGNED_FLOAT</constant> ,
<constant > GL_COMPRESSED_RGB_BPTC_UNSIGNED_FLOAT</constant> ,
<constant > GL_COMPRESSED_RGB8_ETC2</constant> ,
<constant > GL_COMPRESSED_SRGB8_ETC2</constant> ,
<constant > GL_COMPRESSED_RGB8_PUNCHTHROUGH_ALPHA1_ETC2</constant> ,
<constant > GL_COMPRESSED_SRGB8_PUNCHTHROUGH_ALPHA1_ETC2</constant> ,
<constant > GL_COMPRESSED_RGBA8_ETC2_EAC</constant> ,
<constant > GL_COMPRESSED_SRGB8_ALPHA8_ETC2_EAC</constant> ,
<constant > GL_COMPRESSED_R11_EAC</constant> ,
<constant > GL_COMPRESSED_SIGNED_R11_EAC</constant> ,
<constant > GL_COMPRESSED_RG11_EAC</constant> , or
<constant > GL_COMPRESSED_SIGNED_RG11_EAC</constant> .
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</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>
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<para >
<constant > GL_INVALID_VALUE</constant> is generated if <parameter > border</parameter> is not 0.
</para>
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<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 >
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 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 id= "seealso" > <title > See Also</title>
<para >
<citerefentry > <refentrytitle > glActiveTexture</refentrytitle> </citerefentry> ,
<citerefentry > <refentrytitle > glCompressedTexImage1D</refentrytitle> </citerefentry> ,
<citerefentry > <refentrytitle > glCompressedTexImage3D</refentrytitle> </citerefentry> ,
<citerefentry > <refentrytitle > glCompressedTexSubImage1D</refentrytitle> </citerefentry> ,
<citerefentry > <refentrytitle > glCompressedTexSubImage2D</refentrytitle> </citerefentry> ,
<citerefentry > <refentrytitle > glCompressedTexSubImage3D</refentrytitle> </citerefentry> ,
<citerefentry > <refentrytitle > glCopyTexImage1D</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 id= "Copyright" > <title > Copyright</title>
<para >
Copyright <trademark class= "copyright" > </trademark> 1991-2006
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Silicon Graphics, Inc. <trademark class= "copyright" > </trademark> 2011
Khronos Group. This document is licensed under the SGI
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Free Software B License. For details, see
<ulink url= "http://oss.sgi.com/projects/FreeB/" > http://oss.sgi.com/projects/FreeB/</ulink> .
</para>
</refsect1>
</refentry>
