GLGETCOMPRESSEDTEXIM(3G)

NAME
glGetCompressedTexImage, glGetnCompressedTexImage, glGetCompressedTextureImage - return a compressed texture image

C SPECIFICATION

void glGetCompressedTexImage(GLenum target, GLint level, void * pixels);

void glGetnCompressedTexImage(GLenum target, GLint level, GLsizei bufSize, void *pixels);

void glGetCompressedTextureImage(GLuint texture, GLint level, GLsizei bufSize, void *pixels);

PARAMETERS

target
    Specifies the target to which the texture is bound for glGetCompressedTexImage and glGetnCompressedTexImage functions. GL_TEXTURE_1D, GL_TEXTURE_1D_ARRAY, GL_TEXTURE_2D, GL_TEXTURE_2D_ARRAY, GL_TEXTURE_3D, GL_TEXTURE_CUBE_MAP_ARRAY, 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, GL_TEXTURE_RECTANGLE are accepted.

texture
    Specifies the texture object name for glGetCompressedTextureImage function.

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

bufSize
    Specifies the size of the buffer pixels for glGetCompressedTextureImage and glGetnCompressedTexImage functions.

pixels
    Returns the compressed texture image.

DESCRIPTION

glGetCompressedTexImage and glGetnCompressedTexImage return the compressed texture image associated with target and lod into pixels. glGetCompressedTextureImage serves the same purpose, but instead of taking a texture target, it takes the ID of the texture object. pixels should be an array of bufSize bytes for glGetnCompresedTexImage and glGetCompressedTextureImage functions, and of GL_TEXTURE_COMPRESSED_IMAGE_SIZE bytes in case of glGetCompressedTexImage. If the actual data takes less space than bufSize, the remaining bytes will not be touched. target specifies the texture target, to which the texture the data the function should extract the data from is bound to. 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, pixels 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, you can 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_OPERATION is generated by glGetCompressedTextureImage if texture is not the name of an existing texture object.

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

GL_INVALID_OPERATION is generated if glGetCompressedTexImage, glGetnCompressedTexImage, and glGetCompressedTextureImage 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, the buffer storage was not initialized with glBufferStorage using GL_MAP_PERSISTENT_BIT flag, 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

VERSION SUPPORT
 | OpenGL Version
Function / Feature Name | 2.0 | 2.1 | 3.0 | 3.1 | 3.2 | 3.3 | 4.0 | 4.1 | 4.2 | 4.3 | 4.4 | 4.5
glGetCompressedTexImage | ✔ | ✔ | ✔ | ✔ | ✔ | ✔ | ✔ | ✔ | ✔ | ✔ | ✔ | ✔
glGetCompressedTextureImage | - | - | - | - | - | - | - | - | - | - | - | ✔
glGetnCompressedTexImage | - | - | - | - | - | - | - | - | - | - | - | ✔

SEE ALSO

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

COPYRIGHT

Copyright © 1991-2006 Silicon Graphics, Inc. Copyright © 2010-2014 Khronos Group. This document is licensed under the SGI Free Software B License. For details, see https://opencontent.org/openpub/.

COPYRIGHT
Copyright © 1991-2006 Silicon Graphics, Inc.
Copyright © 2010-2014 Khronos Group