How to Add Text or Image Watermarks Using Java Graphics2D

The article explains how to add text or image watermarks to pictures in Java using the Graphics2D API.

Preparation

First import the required classes:

import org.apache.commons.lang3.StringUtils;
import javax.imageio.ImageIO;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.*;
import java.net.URL;
import java.time.LocalDateTime;
import java.time.format.DateTimeFormatter;

Utility class

WatermarkUtils provides three static methods: public static Image readLocalPicture(String path) reads a local file into an Image, throwing RuntimeException if the path is null or reading fails. public static Image readNetworkPicture(String path) creates a URL, reads the image via ImageIO.read(url.openStream()), and validates the result.

public static String manageWatermark(Image image, Integer type, String watermark, int x, int y, String tarImgPath)

creates a BufferedImage with the same dimensions as the source, draws the original image, then depending on type adds either a text watermark (red semi‑transparent, font “微软雅黑” Bold 45pt, drawn at (x,y)) or an image watermark (scaled to 50×50, alpha 0.9). After drawing, the method writes the result as a PNG to tarImgPath and returns a success message.

Testing

Example for a text watermark:

Image image = readLocalPicture("D://test//test.png");
manageWatermark(image, 1, "霸道的程序猿", 150, 50,
    "D://test//testResult" + LocalDateTime.now().format(DateTimeFormatter.ofPattern("yyyyMMddHHmmss")) + ".png");

The coordinates are pixel values that can be determined with an image editor.

Example for an image watermark:

Image image = readLocalPicture("D://test//test.png");
manageWatermark(image, 2, "D://test//mark.jpg", 150, 50,
    "D://test//testResult" + LocalDateTime.now().format(DateTimeFormatter.ofPattern("yyyyMMddHHmmss")) + ".png");

Resulting screenshots show the watermark placed at the specified location.