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# docs.GL

OpenGL 4
OpenGL 3
OpenGL 2
OpenGL ES 3
OpenGL ES 2

# glCompressedTexImage2D

## Name

glCompressedTexImage2D — specify a two-dimensional texture image in a compressed format

## C Specification

`void glCompressedTexImage2D(` | GLenum target,
| GLint level,
| GLenum internalformat,
| GLsizei width,
| GLsizei height,
| GLint border,
| GLsizei imageSize,
| const GLvoid * data`)`;

## Parameters

`target`

  Specifies the target texture. Must be `GL_TEXTURE_2D`, `GL_TEXTURE_CUBE_MAP_POSITIVE_X`, `GL_TEXTURE_CUBE_MAP_NEGATIVE_X`, `GL_TEXTURE_CUBE_MAP_POSITIVE_Y`, `GL_TEXTURE_CUBE_MAP_NEGATIVE_Y`, `GL_TEXTURE_CUBE_MAP_POSITIVE_Z`, or `GL_TEXTURE_CUBE_MAP_NEGATIVE_Z`.

`level`

  Specifies the level-of-detail number. Level 0 is the base image level. Level n is the nth mipmap reduction image.

`internalformat`

  Specifies the format of the compressed image data stored at address `data`.

`width`

  Specifies the width of the texture image. All implementations support 2D and cube-mapped texture images that are at least 2048 texels wide.

`height`

  Specifies the height of the texture image. All implementations support 2D and cube-mapped texture images that are at least 2048 texels high.

`border`

  This value must be 0.

`imageSize`

  Specifies the number of unsigned bytes of image data starting at the address specified by `data`.

`data`

  Specifies a pointer to the compressed image data in memory.

## Description

Texturing allows elements of an image array to be read by shaders.

`glCompressedTexImage2D` loads a previously defined, and retrieved, compressed two-dimensional texture image if `target` is `GL_TEXTURE_2D`, or one of the cube map faces such as `GL_TEXTURE_CUBE_MAP_POSITIVE_X`. (see glTexImage2D).

`internalformat` must be a compressed image format from Table 1 below, or an extension-specified compressed-texture format.

`imageSize` must be appropriate for the `width`, `height` and `depth` of the `internalformat` specified. The size for an ETC/EAC image is given in Table 1 below.

If a non-zero named buffer object is bound to the `GL_PIXEL_UNPACK_BUFFER` target (see glBindBuffer) while a texture image is specified, `data` is treated as a byte offset into the buffer object's data store.

Table 1. Compressed Internal Formats

Compressed Internal Format | Base Internal Format | Image Size
--- | --- | ---
`GL_COMPRESSED_R11_EAC` | `GL_RED` | ceil(`width`/4) * ceil(`height`/4) * 8
`GL_COMPRESSED_SIGNED_R11_EAC` | `GL_RED` | ceil(`width`/4) * ceil(`height`/4) * 8
`GL_COMPRESSED_RG11_EAC` | `GL_RG` | ceil(`width`/4) * ceil(`height`/4) * 16
`GL_COMPRESSED_SIGNED_RG11_EAC` | `GL_RG` | ceil(`width`/4) * ceil(`height`/4) * 16
`GL_COMPRESSED_RGB8_ETC2` | `GL_RGB` | ceil(`width`/4) * ceil(`height`/4) * 8
`GL_COMPRESSED_SRGB8_ETC2` | `GL_RGB` | ceil(`width`/4) * ceil(`height`/4) * 8
`GL_COMPRESSED_RGB8_PUNCHTHROUGH_ALPHA1_ETC2` | `GL_RGBA` | ceil(`width`/4) * ceil(`height`/4) * 8
`GL_COMPRESSED_SRGB8_PUNCHTHROUGH_ALPHA1_ETC2` | `GL_RGBA` | ceil(`width`/4) * ceil(`height`/4) * 8
`GL_COMPRESSED_RGBA8_ETC2_EAC` | `GL_RGBA` | ceil(`width`/4) * ceil(`height`/4) * 16
`GL_COMPRESSED_SRGB8_ALPHA8_ETC2_EAC` | `GL_RGBA` | ceil(`width`/4) * ceil(`height`/4) * 16

## Errors

`GL_INVALID_ENUM` is generated if `internalformat` is not one of the specific compressed internal formats: `GL_COMPRESSED_R11_EAC`, `GL_COMPRESSED_SIGNED_R11_EAC`, `GL_COMPRESSED_RG11_EAC`, `GL_COMPRESSED_SIGNED_RG11_EAC`, `GL_COMPRESSED_RGB8_ETC2`, `GL_COMPRESSED_SRGB8_ETC2`, `GL_COMPRESSED_RGB8_PUNCHTHROUGH_ALPHA1_ETC2`, `GL_COMPRESSED_SRGB8_PUNCHTHROUGH_ALPHA1_ETC2`, `GL_COMPRESSED_RGBA8_ETC2_EAC`, or `GL_COMPRESSED_SRGB8_ALPHA8_ETC2_EAC`.

`GL_INVALID_VALUE` is generated if `imageSize` is not consistent with the format, dimensions, and contents of the specified compressed image data.

`GL_INVALID_VALUE` is generated if `border` is not 0.

`GL_INVALID_OPERATION` is generated if parameter combinations are not supported by the specific compressed internal format as specified in the specific texture compression extension.

`GL_INVALID_OPERATION` is generated if a non-zero buffer object name is bound to the `GL_PIXEL_UNPACK_BUFFER` target and the buffer object's data store is currently mapped.

`GL_INVALID_OPERATION` is generated if a non-zero buffer object name is bound to the `GL_PIXEL_UNPACK_BUFFER` target and the data would be unpacked from the buffer object such that the memory reads required would exceed the data store size.

Undefined results, including abnormal program termination, are generated if `data` is not encoded in a manner consistent with the extension specification defining the internal compression format.

## Associated Gets

glGet with argument `GL_PIXEL_UNPACK_BUFFER_BINDING`

## Tutorials

Sébastien Dominé - Using Texture Compression in OpenGL

## API Version Support

| OpenGL ES API Version
--- | ---
Function Name | 2.0 | 3.0 | 3.1
`glCompressedTexImage2D` | ✔ | ✔ | ✔

## See Also

glActiveTexture, glCompressedTexImage3D, glCompressedTexSubImage2D, glCompressedTexSubImage3D, glCopyTexSubImage2D, glCopyTexSubImage3D, glPixelStorei, glTexImage2D, glTexImage3D, glTexSubImage2D, glTexSubImage3D, glTexParameter

## Copyright

Copyright © 1991-2006 Silicon Graphics, Inc. Copyright © 2010-2014 Khronos Group. This document is licensed under the SGI Free Software B License. For details, see https://web.archive.org/web/20171022161616/http://oss.sgi.com/projects/FreeB/.

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