안드로이드 내부 저장소에 이미지 저장

https://code.i-harness.com/ko-kr/q/ed43ed

https://stackoverflow.com/questions/17674634/saving-and-reading-bitmaps-images-from-internal-memory-in-android/19339672

https://stackoverflow.com/questions/10576930/trying-to-check-if-a-file-exists-in-internal-storage