## 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_PROXY_TEXTURE_2D`, `GL_TEXTURE_1D_ARRAY`, `GL_PROXY_TEXTURE_1D_ARRAY`, `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`, `GL_TEXTURE_CUBE_MAP_NEGATIVE_Z`, or `GL_PROXY_TEXTURE_CUBE_MAP`.

`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 texture and cube map texture images that are at least 16384 texels wide.

`height`

  Specifies the height of the texture image. All implementations support 2D texture and cube map texture images that are at least 16384 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).

If `target` is `GL_TEXTURE_1D_ARRAY`, `data` is treated as an array of compressed 1D textures.

If `target` is `GL_PROXY_TEXTURE_2D`, `GL_PROXY_TEXTURE_1D_ARRAY` or `GL_PROXY_TEXTURE_CUBE_MAP`, no data is read from `data`, but 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 glGetError). To query for an entire mipmap array, use an image array level greater than or equal to 1.

`internalformat` must be a known compressed image format (such as `GL_RGTC`) or an extension-specified compressed-texture format. When a texture is loaded with glTexImage2D using a generic compressed texture format (e.g., `GL_COMPRESSED_RGB`), the GL selects from one of its extensions supporting compressed textures. In order to load the compressed texture image using `glCompressedTexImage2D`, query the compressed texture image's size and format using glGetTexLevelParameter.

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.

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 glTexImage2D. In the following description, denote by b s, b w, b h, and b d, the values of pixel storage modes `GL_UNPACK_COMPRESSED_BLOCK_SIZE`, `GL_UNPACK_COMPRESSED_BLOCK_WIDTH`, `GL_UNPACK_COMPRESSED_BLOCK_HEIGHT`, and `GL_UNPACK_COMPRESSED_BLOCK_DEPTH`, respectively. b s is the compressed block size in bytes; b w, b h, and b d are the compressed block width, height, and depth in pixels.

By default the pixel storage modes `GL_UNPACK_ROW_LENGTH`, `GL_UNPACK_SKIP_ROWS`, `GL_UNPACK_SKIP_PIXELS`, `GL_UNPACK_IMAGE_HEIGHT` and `GL_UNPACK_SKIP_IMAGES` are ignored for compressed images. To enable `GL_UNPACK_SKIP_PIXELS` and `GL_UNPACK_ROW_LENGTH`, b s and b w must both be non-zero. To also enable `GL_UNPACK_SKIP_ROWS` and `GL_UNPACK_IMAGE_HEIGHT`, b h must be non-zero. To also enable `GL_UNPACK_SKIP_IMAGES`, b d must be non-zero. All parameters must be consistent with the compressed format to produce the desired results.

When selecting a sub-rectangle from a compressed image:

- the value of `GL_UNPACK_SKIP_PIXELS` must be a multiple of b w;
- the value of `GL_UNPACK_SKIP_ROWS` must be a multiple of b w.

`imageSize` must be equal to:

b s × width b w × height b h

## Notes

The specific compressed internal formats `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`, `GL_COMPRESSED_SRGB8_ALPHA8_ETC2_EAC`, `GL_COMPRESSED_R11_EAC`, `GL_COMPRESSED_SIGNED_R11_EAC`, `GL_COMPRESSED_RG11_EAC`, and `GL_COMPRESSED_SIGNED_RG11_EAC` are available only if the GL version is 4.3 or higher.

## Errors

`GL_INVALID_ENUM` is generated if `internalformat` is not one of the specific compressed internal formats: `GL_COMPRESSED_RED_RGTC1`, `GL_COMPRESSED_SIGNED_RED_RGTC1`, `GL_COMPRESSED_RG_RGTC2`, `GL_COMPRESSED_SIGNED_RG_RGTC2`. `GL_COMPRESSED_RGBA_BPTC_UNORM`, `GL_COMPRESSED_SRGB_ALPHA_BPTC_UNORM`, `GL_COMPRESSED_RGB_BPTC_SIGNED_FLOAT`, `GL_COMPRESSED_RGB_BPTC_UNSIGNED_FLOAT`, `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`, `GL_COMPRESSED_SRGB8_ALPHA8_ETC2_EAC`, `GL_COMPRESSED_R11_EAC`, `GL_COMPRESSED_SIGNED_R11_EAC`, `GL_COMPRESSED_RG11_EAC`, or `GL_COMPRESSED_SIGNED_RG11_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

glGetCompressedTexImage

glGet with argument `GL_TEXTURE_COMPRESSED`

glGet with argument `GL_PIXEL_UNPACK_BUFFER_BINDING`

glGetTexLevelParameter with arguments `GL_TEXTURE_INTERNAL_FORMAT` and `GL_TEXTURE_COMPRESSED_IMAGE_SIZE`

## See Also

glActiveTexture, glCompressedTexImage1D, glCompressedTexImage3D, glCompressedTexSubImage1D, glCompressedTexSubImage2D, glCompressedTexSubImage3D, glCopyTexImage1D, glCopyTexSubImage1D, glCopyTexSubImage2D, glCopyTexSubImage3D, glPixelStore, glTexImage2D, glTexImage3D, glTexSubImage1D, glTexSubImage2D, glTexSubImage3D, glTexParameter

## Copyright

Copyright © 1991-2006 Silicon Graphics, Inc. © 2011 Khronos Group. This document is licensed under the SGI Free Software B License. For details, see http://oss.sgi.com/projects/FreeB/.