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

`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.

internalformat must be a known compressed image format (such as `GL_RGTC`) or an extension-specified compressed-texture format. The format of the compressed texture image is selected by the GL implementation that compressed it (see glTexImage2D) and should be queried at the time the texture was compressed with 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.

## Errors

`GL_INVALID_ENUM` is generated if internalformat is of the generic compressed internal formats: `GL_COMPRESSED_RED`, `GL_COMPRESSED_RG`, `GL_COMPRESSED_RGB`, `GL_COMPRESSED_RGBA`. `GL_COMPRESSED_SRGB`, or `GL_COMPRESSED_SRGB_ALPHA`.

`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 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, glCompressedTexImage2D, glCompressedTexImage3D, glCompressedTexSubImage1D, glCompressedTexSubImage3D, glCopyTexImage1D, glCopyTexImage2D, glCopyTexSubImage1D, glCopyTexSubImage2D, glCopyTexSubImage3D, glPixelStore, glTexImage2D, glTexImage3D, glTexSubImage1D, glTexSubImage2D, glTexSubImage3D, 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/.