'\" t
.\"     Title: glCompressedTexImage2D
.\"    Author: [FIXME: author] [see http://docbook.sf.net/el/author]
.\" Generator: DocBook XSL Stylesheets v1.79.1 <http://docbook.sf.net/>
.\"      Date: 01/03/2018
.\"    Manual: [FIXME: manual]
.\"    Source: [FIXME: source]
.\"  Language: English
.\"
.TH "GLCOMPRESSEDTEXIMAGE" "3G" "01/03/2018" "[FIXME: source]" "[FIXME: manual]"
.\" -----------------------------------------------------------------
.\" * Define some portability stuff
.\" -----------------------------------------------------------------
.\" ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
.\" http://bugs.debian.org/507673
.\" http://lists.gnu.org/archive/html/groff/2009-02/msg00013.html
.\" ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
.ie \n(.g .ds Aq \(aq
.el       .ds Aq '
.\" -----------------------------------------------------------------
.\" * set default formatting
.\" -----------------------------------------------------------------
.\" disable hyphenation
.nh
.\" disable justification (adjust text to left margin only)
.ad l
.\" -----------------------------------------------------------------
.\" * MAIN CONTENT STARTS HERE *
.\" -----------------------------------------------------------------
.SH "NAME"
glCompressedTexImage2D \- specify a two\-dimensional texture image in a compressed format
.SH "C SPECIFICATION"
.HP \w'void\ glCompressedTexImage2D('u
.BI "void glCompressedTexImage2D(GLenum\ " "target" ", GLint\ " "level" ", GLenum\ " "internalformat" ", GLsizei\ " "width" ", GLsizei\ " "height" ", GLint\ " "border" ", GLsizei\ " "imageSize" ", const\ GLvoid\ *\ " "data" ");"
.SH "PARAMETERS"
.PP
\fItarget\fR
.RS 4
Specifies the target texture\&. Must be
\fBGL_TEXTURE_2D\fR,
\fBGL_PROXY_TEXTURE_2D\fR,
\fBGL_TEXTURE_1D_ARRAY\fR,
\fBGL_PROXY_TEXTURE_1D_ARRAY\fR,
\fBGL_TEXTURE_CUBE_MAP_POSITIVE_X\fR,
\fBGL_TEXTURE_CUBE_MAP_NEGATIVE_X\fR,
\fBGL_TEXTURE_CUBE_MAP_POSITIVE_Y\fR,
\fBGL_TEXTURE_CUBE_MAP_NEGATIVE_Y\fR,
\fBGL_TEXTURE_CUBE_MAP_POSITIVE_Z\fR,
\fBGL_TEXTURE_CUBE_MAP_NEGATIVE_Z\fR, or
\fBGL_PROXY_TEXTURE_CUBE_MAP\fR\&.
.RE
.PP
\fIlevel\fR
.RS 4
Specifies the level\-of\-detail number\&. Level 0 is the base image level\&. Level
\fIn\fR
is the
\fIn\fRth mipmap reduction image\&.
.RE
.PP
\fIinternalformat\fR
.RS 4
Specifies the format of the compressed image data stored at address
\fIdata\fR\&.
.RE
.PP
\fIwidth\fR
.RS 4
Specifies the width of the texture image\&. All implementations support 2D texture and cube map texture images that are at least 16384 texels wide\&.
.RE
.PP
\fIheight\fR
.RS 4
Specifies the height of the texture image\&. All implementations support 2D texture and cube map texture images that are at least 16384 texels high\&.
.RE
.PP
\fIborder\fR
.RS 4
This value must be 0\&.
.RE
.PP
\fIimageSize\fR
.RS 4
Specifies the number of unsigned bytes of image data starting at the address specified by
\fIdata\fR\&.
.RE
.PP
\fIdata\fR
.RS 4
Specifies a pointer to the compressed image data in memory\&.
.RE
.SH "DESCRIPTION"
.PP
Texturing allows elements of an image array to be read by shaders\&.
.PP
\fBglCompressedTexImage2D\fR
loads a previously defined, and retrieved, compressed two\-dimensional texture image if
\fItarget\fR
is
\fBGL_TEXTURE_2D\fR, or one of the cube map faces such as
\fBGL_TEXTURE_CUBE_MAP_POSITIVE_X\fR\&. (see
\fBglTexImage2D\fR())\&.
.PP
If
\fItarget\fR
is
\fBGL_TEXTURE_1D_ARRAY\fR,
\fIdata\fR
is treated as an array of compressed 1D textures\&.
.PP
If
\fItarget\fR
is
\fBGL_PROXY_TEXTURE_2D\fR,
\fBGL_PROXY_TEXTURE_1D_ARRAY\fR
or
\fBGL_PROXY_TEXTURE_CUBE_MAP\fR, no data is read from
\fIdata\fR, but all of the texture image state is recalculated, checked for consistency, and checked against the implementation\*(Aqs 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
\fBglGetError\fR())\&. To query for an entire mipmap array, use an image array level greater than or equal to 1\&.
.PP
\fIinternalformat\fR
must be a known compressed image format (such as
\fBGL_RGTC\fR) or an extension\-specified compressed\-texture format\&. When a texture is loaded with
\fBglTexImage2D\fR()
using a generic compressed texture format (e\&.g\&.,
\fBGL_COMPRESSED_RGB\fR), the GL selects from one of its extensions supporting compressed textures\&. In order to load the compressed texture image using
\fBglCompressedTexImage2D\fR, query the compressed texture image\*(Aqs size and format using
\fBglGetTexLevelParameter\fR()\&.
.PP
If a non\-zero named buffer object is bound to the
\fBGL_PIXEL_UNPACK_BUFFER\fR
target (see
\fBglBindBuffer\fR()) while a texture image is specified,
\fIdata\fR
is treated as a byte offset into the buffer object\*(Aqs data store\&.
.PP
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
\fBglTexImage2D\fR()\&. In the following description, denote by
bs,
bw,
bh, and
bd, the values of pixel storage modes
\fBGL_UNPACK_COMPRESSED_BLOCK_SIZE\fR,
\fBGL_UNPACK_COMPRESSED_BLOCK_WIDTH\fR,
\fBGL_UNPACK_COMPRESSED_BLOCK_HEIGHT\fR, and
\fBGL_UNPACK_COMPRESSED_BLOCK_DEPTH\fR, respectively\&.
bs
is the compressed block size in bytes;
bw,
bh, and
bd
are the compressed block width, height, and depth in pixels\&.
.PP
By default the pixel storage modes
\fBGL_UNPACK_ROW_LENGTH\fR,
\fBGL_UNPACK_SKIP_ROWS\fR,
\fBGL_UNPACK_SKIP_PIXELS\fR,
\fBGL_UNPACK_IMAGE_HEIGHT\fR
and
\fBGL_UNPACK_SKIP_IMAGES\fR
are ignored for compressed images\&. To enable
\fBGL_UNPACK_SKIP_PIXELS\fR
and
\fBGL_UNPACK_ROW_LENGTH\fR,
bs
and
bw
must both be non\-zero\&. To also enable
\fBGL_UNPACK_SKIP_ROWS\fR
and
\fBGL_UNPACK_IMAGE_HEIGHT\fR,
bh
must be non\-zero\&. To also enable
\fBGL_UNPACK_SKIP_IMAGES\fR,
bd
must be non\-zero\&. All parameters must be consistent with the compressed format to produce the desired results\&.
.PP
When selecting a sub\-rectangle from a compressed image:
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
The value of
\fBGL_UNPACK_SKIP_PIXELS\fR
must be a multiple of
bw;
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
the value of
\fBGL_UNPACK_SKIP_ROWS\fR
must be a multiple of
bw\&.
.RE
.PP
\fIimageSize\fR
must be equal to:
.PP
b s \(mu width b w \(mu height b h
.SH "NOTES"
.PP
The specific compressed internal formats
\fBGL_COMPRESSED_RGB8_ETC2\fR,
\fBGL_COMPRESSED_SRGB8_ETC2\fR,
\fBGL_COMPRESSED_RGB8_PUNCHTHROUGH_ALPHA1_ETC2\fR,
\fBGL_COMPRESSED_SRGB8_PUNCHTHROUGH_ALPHA1_ETC2\fR,
\fBGL_COMPRESSED_RGBA8_ETC2_EAC\fR,
\fBGL_COMPRESSED_SRGB8_ALPHA8_ETC2_EAC\fR,
\fBGL_COMPRESSED_R11_EAC\fR,
\fBGL_COMPRESSED_SIGNED_R11_EAC\fR,
\fBGL_COMPRESSED_RG11_EAC\fR, and
\fBGL_COMPRESSED_SIGNED_RG11_EAC\fR
are available only if the GL version is 4\&.3 or higher\&.
.SH "ERRORS"
.PP
\fBGL_INVALID_ENUM\fR
is generated if
\fIinternalformat\fR
is not one of the specific compressed internal formats:
\fBGL_COMPRESSED_RED_RGTC1\fR,
\fBGL_COMPRESSED_SIGNED_RED_RGTC1\fR,
\fBGL_COMPRESSED_RG_RGTC2\fR,
\fBGL_COMPRESSED_SIGNED_RG_RGTC2\fR\&.
\fBGL_COMPRESSED_RGBA_BPTC_UNORM\fR,
\fBGL_COMPRESSED_SRGB_ALPHA_BPTC_UNORM\fR,
\fBGL_COMPRESSED_RGB_BPTC_SIGNED_FLOAT\fR,
\fBGL_COMPRESSED_RGB_BPTC_UNSIGNED_FLOAT\fR,
\fBGL_COMPRESSED_RGB8_ETC2\fR,
\fBGL_COMPRESSED_SRGB8_ETC2\fR,
\fBGL_COMPRESSED_RGB8_PUNCHTHROUGH_ALPHA1_ETC2\fR,
\fBGL_COMPRESSED_SRGB8_PUNCHTHROUGH_ALPHA1_ETC2\fR,
\fBGL_COMPRESSED_RGBA8_ETC2_EAC\fR,
\fBGL_COMPRESSED_SRGB8_ALPHA8_ETC2_EAC\fR,
\fBGL_COMPRESSED_R11_EAC\fR,
\fBGL_COMPRESSED_SIGNED_R11_EAC\fR,
\fBGL_COMPRESSED_RG11_EAC\fR, or
\fBGL_COMPRESSED_SIGNED_RG11_EAC\fR\&.
.PP
\fBGL_INVALID_VALUE\fR
is generated if
\fIimageSize\fR
is not consistent with the format, dimensions, and contents of the specified compressed image data\&.
.PP
\fBGL_INVALID_VALUE\fR
is generated if
\fIborder\fR
is not 0\&.
.PP
\fBGL_INVALID_OPERATION\fR
is generated if parameter combinations are not supported by the specific compressed internal format as specified in the specific texture compression extension\&.
.PP
\fBGL_INVALID_OPERATION\fR
is generated if a non\-zero buffer object name is bound to the
\fBGL_PIXEL_UNPACK_BUFFER\fR
target and the buffer object\*(Aqs data store is currently mapped\&.
.PP
\fBGL_INVALID_OPERATION\fR
is generated if a non\-zero buffer object name is bound to the
\fBGL_PIXEL_UNPACK_BUFFER\fR
target and the data would be unpacked from the buffer object such that the memory reads required would exceed the data store size\&.
.PP
Undefined results, including abnormal program termination, are generated if
\fIdata\fR
is not encoded in a manner consistent with the extension specification defining the internal compression format\&.
.SH "ASSOCIATED GETS"
.PP
\fBglGetCompressedTexImage\fR()
.PP
\fBglGet\fR()
with argument
\fBGL_TEXTURE_COMPRESSED\fR
.PP
\fBglGet\fR()
with argument
\fBGL_PIXEL_UNPACK_BUFFER_BINDING\fR
.PP
\fBglGetTexLevelParameter\fR()
with arguments
\fBGL_TEXTURE_INTERNAL_FORMAT\fR
and
\fBGL_TEXTURE_COMPRESSED_IMAGE_SIZE\fR
.SH "VERSION SUPPORT"
.TS
allbox tab(:);
lB cB s s s s s s s s s s s
lB cB cB cB cB cB cB cB cB cB cB cB cB.
T{

T}:T{
\fBOpenGL Version\fR
T}
T{
\fBFunction / Feature Name\fR
T}:T{
\fB2\&.0\fR
T}:T{
\fB2\&.1\fR
T}:T{
\fB3\&.0\fR
T}:T{
\fB3\&.1\fR
T}:T{
\fB3\&.2\fR
T}:T{
\fB3\&.3\fR
T}:T{
\fB4\&.0\fR
T}:T{
\fB4\&.1\fR
T}:T{
\fB4\&.2\fR
T}:T{
\fB4\&.3\fR
T}:T{
\fB4\&.4\fR
T}:T{
\fB4\&.5\fR
T}
.T&
l c c c c c c c c c c c c.
T{
\fBglCompressedTexImage2D\fR
T}:T{
✔
T}:T{
✔
T}:T{
✔
T}:T{
✔
T}:T{
✔
T}:T{
✔
T}:T{
✔
T}:T{
✔
T}:T{
✔
T}:T{
✔
T}:T{
✔
T}:T{
✔
T}
.TE
.sp 1
.SH "SEE ALSO"
.PP
\fBglActiveTexture\fR(),
\fBglCompressedTexImage1D\fR(),
\fBglCompressedTexImage3D\fR(),
\fBglCompressedTexSubImage1D\fR(),
\fBglCompressedTexSubImage2D\fR(),
\fBglCompressedTexSubImage3D\fR(),
\fBglCopyTexImage1D\fR(),
\fBglCopyTexSubImage1D\fR(),
\fBglCopyTexSubImage2D\fR(),
\fBglCopyTexSubImage3D\fR(),
\fBglPixelStore\fR(),
\fBglTexImage2D\fR(),
\fBglTexImage3D\fR(),
\fBglTexSubImage1D\fR(),
\fBglTexSubImage2D\fR(),
\fBglTexSubImage3D\fR(),
\fBglTexParameter\fR()
.SH "COPYRIGHT"
.PP
Copyright
\(co
1991\-2006 Silicon Graphics, Inc\&. Copyright
\(co
2011\-2014 Khronos Group\&. This document is licensed under the SGI Free Software B License\&. For details, see
\m[blue]\fBhttp://oss\&.sgi\&.com/projects/FreeB/\fR\m[]\&.
.SH "COPYRIGHT"
.br
Copyright \(co 1991-2006 Silicon Graphics, Inc.
.br
Copyright \(co 2011-2014 Khronos Group
.br