After a downtrend market at the bottom level when a bearish candle covered by next bullish candle body,then we can say here for bullish engulfing.
In this picture 1, 2 length of the body of last bullish candle. Previous bearish candle fully covered or engulfed by last bullish candle.
This kind of candle formation is called bullish engulfing.
Body engulfed by body is enough indication for bullish engulfing pattern.
Previous Candle can be doji in that case last candle should be bullish Marubozu