glGetCompressedTexImage

glGetCompressedTexImage: man3/glGetCompressedTexImage.xml

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.