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 © 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/.
