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GLGETCOMPRESSEDTEXIM(3G)                         OpenGL 3.3                         GLGETCOMPRESSEDTEXIM(3G)



NAME
       glGetCompressedTexImage - return a compressed texture image

C SPECIFICATION
       void glGetCompressedTexImage(GLenum target, GLint lod, GLvoid * img);

PARAMETERS
       target
           Specifies which texture is to be obtained.  GL_TEXTURE_1D, GL_TEXTURE_2D, GL_TEXTURE_3D,
           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, and
           GL_TEXTURE_CUBE_MAP_NEGATIVE_Z are accepted.

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

       img
           Returns the compressed texture image.

DESCRIPTION
       glGetCompressedTexImage returns the compressed texture image associated with target and lod into img.
       img should be an array of GL_TEXTURE_COMPRESSED_IMAGE_SIZE bytes.  target specifies whether the
       desired texture image was one specified by glTexImage1D() (GL_TEXTURE_1D), glTexImage2D()
       (GL_TEXTURE_2D or any of GL_TEXTURE_CUBE_MAP_*), or glTexImage3D() (GL_TEXTURE_3D).  lod specifies
       the level-of-detail number of the desired image.

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

       To minimize errors, first verify that the texture is compressed by calling glGetTexLevelParameter()
       with argument GL_TEXTURE_COMPRESSED. If the texture is compressed, then determine the amount of
       memory required to store the compressed texture by calling glGetTexLevelParameter() with argument
       GL_TEXTURE_COMPRESSED_IMAGE_SIZE. Finally, retrieve the internal format of the texture by calling
       glGetTexLevelParameter() with argument GL_TEXTURE_INTERNAL_FORMAT. To store the texture for later
       use, associate the internal format and size with the retrieved texture image. These data can be used
       by the respective texture or subtexture loading routine used for loading target textures.

ERRORS
       GL_INVALID_VALUE is generated if lod is less than zero or greater than the maximum number of LODs
       permitted by the implementation.


       GL_INVALID_OPERATION is generated if glGetCompressedTexImage is used to retrieve a texture that is in
       an uncompressed internal format.


       GL_INVALID_OPERATION is generated if a non-zero buffer object name is bound to the
       GL_PIXEL_PACK_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_PACK_BUFFER target and the data would be packed to the buffer object such that the memory
       writes required would exceed the data store size.

ASSOCIATED GETS
       glGetTexLevelParameter() with argument GL_TEXTURE_COMPRESSED


       glGetTexLevelParameter() with argument GL_TEXTURE_COMPRESSED_IMAGE_SIZE


       glGetTexLevelParameter() with argument GL_TEXTURE_INTERNAL_FORMAT


       glGet() with argument GL_PIXEL_PACK_BUFFER_BINDING

SEE ALSO
       glActiveTexture(), glCompressedTexImage1D(), glCompressedTexImage2D(), glCompressedTexImage3D(),
       glCompressedTexSubImage1D(), glCompressedTexSubImage2D(), glCompressedTexSubImage3D(),
       glReadPixels(), glTexImage1D(), glTexImage2D(), glTexImage3D(), glTexParameter(), glTexSubImage1D(),
       glTexSubImage2D(), glTexSubImage3D()


COPYRIGHT
       Copyright (C) 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/.



OpenGL 3.3                                       03/08/2011                         GLGETCOMPRESSEDTEXIM(3G)