glGetCompressedTexImage, glGetnCompressedTexImage, glGetCompressedTextureImage - return a compressed

glGetTexLevelParameter() with argument GL_TEXTURE_COMPRESSEDglGetTexLevelParameter() with argument GL_TEXTURE_COMPRESSED_IMAGE_SIZEglGetTexLevelParameter() with argument GL_TEXTURE_INTERNAL_FORMATglGet() with argument GL_PIXEL_PACK_BUFFER_BINDING

voidglGetCompressedTexImage(GLenumtarget,GLintlevel,GLvoid*pixels);voidglGetnCompressedTexImage(GLenumtarget,GLintlevel,GLsizeibufSize,void*pixels);voidglGetCompressedTextureImage(GLuinttexture,GLintlevel,GLsizeibufSize,void*pixels);

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

[FIXME: source]                                    11/18/2024                           GLGETCOMPRESSEDTEXIM(3G)

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.

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.

       glGetCompressedTexImage, glGetnCompressedTexImage, glGetCompressedTextureImage - return a compressed
       texture image

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.

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

       ┌─────────────────────────────┬───────────────────────────────────────────────────────────────────────┐
       │                             │                OpenGLVersion                                         │
       ├─────────────────────────────┼─────┬─────┬─────┬─────┬─────┬─────┬─────┬─────┬─────┬─────┬─────┬─────┤
       │ Function                    │ 2.0 │ 2.1 │ 3.0 │ 3.1 │ 3.2 │ 3.3 │ 4.0 │ 4.1 │ 4.2 │ 4.3 │ 4.4 │ 4.5 │
       │ /                           │     │     │     │     │     │     │     │     │     │     │     │     │
       │ Feature                     │     │     │     │     │     │     │     │     │     │     │     │     │
       │ Name                        │     │     │     │     │     │     │     │     │     │     │     │     │
       ├─────────────────────────────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┤
       │ glGetCompressedTexImage     │  ✔  │  ✔  │  ✔  │  ✔  │  ✔  │  ✔  │  ✔  │  ✔  │  ✔  │  ✔  │  ✔  │  ✔  │
       ├─────────────────────────────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┤
       │ glGetCompressedTextureImage │  -  │  -  │  -  │  -  │  -  │  -  │  -  │  -  │  -  │  -  │  -  │  ✔  │
       ├─────────────────────────────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┤
       │ glGetnCompressedTexImage    │  -  │  -  │  -  │  -  │  -  │  -  │  -  │  -  │  -  │  -  │  -  │  ✔  │
       └─────────────────────────────┴─────┴─────┴─────┴─────┴─────┴─────┴─────┴─────┴─────┴─────┴─────┴─────┘