watermark

- image에 watermark 넣기

https://github.com/purab/SpringBoot-upload-image-resize-watermark-tutorial


https://handcoding.tistory.com/148


https://blog.conholdate.com/ko/total/add-watermark-to-images-using-java/

https://blog.groupdocs.com/ko/watermark/add-watermark-to-images-in-java/


- pdf에 watermark 넣기
https://www.baeldung.com/java-watermarks-with-itext

Using Watermarks with iText in Java | Baeldung