glGetCompressedTexImage

glGetCompressedTexImage: man4/glGetCompressedTexImage.xml

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.