## Name

glCompressedTexSubImage1D — specify a one-dimensional texture subimage in a compressed format

## C Specification

`void glCompressedTexSubImage1D(` | GLenum target,
| GLint level,
| GLint xoffset,
| GLsizei width,
| GLenum format,
| GLsizei imageSize,
| const GLvoid * data`)`;

## Parameters

`target`

  Specifies the target texture. Must be `GL_TEXTURE_1D`.

`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.

`width`

  Specifies the width 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.

`glCompressedTexSubImage1D` redefines a contiguous subregion of an existing one-dimensional texture image. The texels referenced by `data` replace the portion of the existing texture array with x indices `xoffset` and xoffset + width - 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 glTexImage1D), 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 not one 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, glCompressedTexSubImage2D, 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/.