question: public Bitmap decodeFileDescriptor ( FileDescriptor fd , BitmapFactory . Options options ) { if ( options . mCancel ) { return null ; } Thread thread = Thread . currentThread ( ) ; if ( ! canThreadDecoding ( thread ) ) { Log . d ( TAG , "Thread " + thread + " is not allowed to decode." ) ; return null ; } setDecodingOptions ( thread , options ) ; Bitmap b = BitmapFactory . decodeFileDescriptor ( fd , null , options ) ; removeDecodingOptions ( thread ) ; return b ; }
target:  The real place to delegate bitmap decoding to BitmapFactory.