1991-2006
Silicon Graphics, Inc.
glCompressedTexSubImage2D
3G

# glCompressedTexSubImage2D

specify a two-dimensional texture subimage in a compressed format

## C Specification

                    void glCompressedTexSubImage2D
                    GLenum target
                    GLint level
                    GLint xoffset
                    GLint yoffset
                    GLsizei width
                    GLsizei height
                    GLenum format
                    GLsizei imageSize
                    const GLvoid * data

## Parameters

`target`

  Specifies the target texture of the active texture unit. 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.

`xoffset`

  Specifies a texel offset in the x direction within the texture array.

`yoffset`

  Specifies a texel offset in the y direction within the texture array.

`width`

  Specifies the width of the texture subimage.

`height`

  Specifies the height of the texture subimage.

`format`

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

`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 maps a portion of a specified texture image onto each graphical primitive for which texturing is active. Texturing is active when the current fragment shader or vertex shader makes use of built-in texture lookup functions.

`glCompressedTexSubImage2D` redefines a contiguous subregion of an existing two-dimensional texture image. The texels referenced by `data` replace the portion of the existing texture array with x indices `xoffset` and xoffset + width - 1 , and the y indices `yoffset` and yoffset + height - 1 , inclusive. This region may not include any texels outside the range of the texture array as it was originally specified. It is not an error to specify a subtexture with width of 0, but such a specification has no effect.

`format` must be the same extension-specified compressed-texture format previously specified by glCompressedTexImage2D.

## Notes

`glCompressedTexSubImage2D` specifies a two-dimensional or cube-map texture for the current texture unit, specified with glActiveTexture.

## Errors

`GL_INVALID_ENUM` is generated if `target` is not `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`.

`GL_INVALID_ENUM` is generated if `format` is not a supported format returned in `GL_COMPRESSED_TEXTURE_FORMATS`.

`GL_INVALID_VALUE` is generated if `level` is less than 0.

`GL_INVALID_VALUE` may be generated if `level` is greater than log 2 &it; max , where max is the returned value of `GL_MAX_TEXTURE_SIZE` when `target` is `GL_TEXTURE_2D` or `GL_MAX_CUBE_MAP_TEXTURE_SIZE` when `target` is not `GL_TEXTURE_2D`.

`GL_INVALID_VALUE` is generated if xoffset < 0 , xoffset + width > w , yoffset < 0 , or yoffset + height > h , where w is the width and h is the height of the texture image being modified.

`GL_INVALID_VALUE` is generated if `width` or `height` is less than 0.

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

`GL_INVALID_OPERATION` is generated if the texture array has not been defined by a previous glCompressedTexImage2D operation whose `internalformat` matches the `format` of `glCompressedTexSubImage2D`.

`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.

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 arguments `GL_NUM_COMPRESSED_TEXTURE_FORMATS` and `GL_COMPRESSED_TEXTURE_FORMATS`

glGet with argument `GL_MAX_TEXTURE_SIZE` or `GL_MAX_CUBE_MAP_TEXTURE_SIZE`

## See Also

glActiveTexture, glCompressedTexImage2D, glCopyTexImage2D, glCopyTexSubImage2D, glTexImage2D, glTexSubImage2D, glTexParameter

## Copyright

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