Clean up resources

After you finish using the image library, clean up by freeing any memory that was allocated by this library in the img_t structure. For example:

• If img_t::flags and IMG_DIRECT are set, you need to free img_t::access.direct.data.
• If img_t::format and IMG_FMT_PALETTE are set, and img_t::npalette is greater than zero (0), you need to free img_t::palette.
• Use img_lib_detach() to detach from the image library and free all associated resources.
• If you created an input stream manually using io_open(), use io_close() to close the input stream.
• If you used screen buffers to display the image, free the buffers and any associated memory that is used by the Screen and Windowing API functions.