Adding Text or Image as Watermark to an Image in Java

The following tutorial demonstrates how to add a watermark to an image in java. We show you two examples. The first example adds a text watermark to an image. The second adds an image watermark to an image.

We distinguish PNG images from JPG images, because PNG images support transparency. In case of PNG images we set the image type to BufferedImage.TYPE_INT_ARGB. All other images we set the image type to BufferedImage.TYPE_INT_RGB.

Adding Text as Watermark to an Image

The following example adds a text watermark to an image.

package com.memorynotfound.image;

import javax.imageio.ImageIO;
import java.awt.*;
import java.awt.geom.Rectangle2D;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;

public class AddTextWatermark {

    public static void main(String... args) throws IOException {

        // overlay settings
        String text = "\u00a9 memorynotfound.com";
        File input = new File("/tmp/duke.jpg");
        File output = new File("/tmp/duke-text-watermarked.jpg");

        // adding text as overlay to an image
        addTextWatermark(text, "jpg", input, output);
    }

    private static void addTextWatermark(String text, String type, File source, File destination) throws IOException {
        BufferedImage image = ImageIO.read(source);

        // determine image type and handle correct transparency
        int imageType = "png".equalsIgnoreCase(type) ? BufferedImage.TYPE_INT_ARGB : BufferedImage.TYPE_INT_RGB;
        BufferedImage watermarked = new BufferedImage(image.getWidth(), image.getHeight(), imageType);

        // initializes necessary graphic properties
        Graphics2D w = (Graphics2D) watermarked.getGraphics();
        w.drawImage(image, 0, 0, null);
        AlphaComposite alphaChannel = AlphaComposite.getInstance(AlphaComposite.SRC_OVER, 0.4f);
        w.setComposite(alphaChannel);
        w.setColor(Color.GRAY);
        w.setFont(new Font(Font.SANS_SERIF, Font.BOLD, 26));
        FontMetrics fontMetrics = w.getFontMetrics();
        Rectangle2D rect = fontMetrics.getStringBounds(text, w);

        // calculate center of the image
        int centerX = (image.getWidth() - (int) rect.getWidth()) / 2;
        int centerY = image.getHeight() / 2;

        // add text overlay to the image
        w.drawString(text, centerX, centerY);
        ImageIO.write(watermarked, type, destination);
        w.dispose();
    }


}

Text Watermark Result

To demonstrate the result, we added the following table.

duke.png (original)	duke-text-watermarked.png	duke-text-watermarked.jpg
Size: 9KB	Size: 13KB	Size: 16KB

Adding an Image Watermark to an Image

The following example adds an image watermark to an image.

package com.memorynotfound.image;

import javax.imageio.ImageIO;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;

public class AddImageWatermark {

    public static void main(String... args) throws IOException {

        // overlay settings
        File input = new File("/tmp/duke.png");
        File overlay = new File("/tmp/watermark.png");
        File output = new File("/tmp/duke-image-watermarked.png");

        // adding text as overlay to an image
        addImageWatermark(overlay, "png", input, output);
    }

    private static void addImageWatermark(File watermark, String type, File source, File destination) throws IOException {
        BufferedImage image = ImageIO.read(source);
        BufferedImage overlay = resize(ImageIO.read(watermark), 150, 150);

        // determine image type and handle correct transparency
        int imageType = "png".equalsIgnoreCase(type) ? BufferedImage.TYPE_INT_ARGB : BufferedImage.TYPE_INT_RGB;
        BufferedImage watermarked = new BufferedImage(image.getWidth(), image.getHeight(), imageType);

        // initializes necessary graphic properties
        Graphics2D w = (Graphics2D) watermarked.getGraphics();
        w.drawImage(image, 0, 0, null);
        AlphaComposite alphaChannel = AlphaComposite.getInstance(AlphaComposite.SRC_OVER, 0.4f);
        w.setComposite(alphaChannel);

        // calculates the coordinate where the String is painted
        int centerX = image.getWidth() / 2;
        int centerY = image.getHeight() / 2;

        // add text watermark to the image
        w.drawImage(overlay, centerX, centerY, null);
        ImageIO.write(watermarked, type, destination);
        w.dispose();
    }

    private static BufferedImage resize(BufferedImage img, int height, int width) {
        Image tmp = img.getScaledInstance(width, height, Image.SCALE_SMOOTH);
        BufferedImage resized = new BufferedImage(width, height, BufferedImage.TYPE_INT_ARGB);
        Graphics2D g2d = resized.createGraphics();
        g2d.drawImage(tmp, 0, 0, null);
        g2d.dispose();
        return resized;
    }

}

Image Watermark Result

To demonstrate the result, we added the following table.

duke.png (original)	duke-image-watermarked.png	duke-image-watermarked.jpg
Size: 9KB	Size: 26KB	Size: 13KB

References

• BufferedImage JavaDoc
• Graphics2D JavaDoc
• ImageIO JavaDoc
• AlphaComposite JavaDoc
• FontMetrics JavaDoc