在Java中的MySqlDB中向图像添加水印

Question

In my project , I'm trying to add watermark to existing image in Mysql Db Table with column( Blob ).

I used below method to add watermark to any image file, and it works fine.

public static void addTextWatermark(String text, File sourceImageFile, File destImageFile) {
        try {
            BufferedImage sourceImage = ImageIO.read(sourceImageFile);
            Graphics2D g2d = (Graphics2D) sourceImage.getGraphics();

            // initializes necessary graphic properties
            AlphaComposite alphaChannel = AlphaComposite.getInstance(AlphaComposite.SRC_OVER, 0.3f);
            g2d.setComposite(alphaChannel);
            g2d.setColor(Color.WHITE);
            g2d.setFont(new Font("Arial", Font.BOLD, 64));
            FontMetrics fontMetrics = g2d.getFontMetrics();
            Rectangle2D rect = fontMetrics.getStringBounds(text, g2d);

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

            // paints the textual watermark
            g2d.drawString(text, centerX, centerY);

            ImageIO.write(sourceImage, "png", destImageFile);
            g2d.dispose();

            System.out.println("The tex watermark is added to the image.");

        } catch (IOException ex) {
            System.err.println(ex);
        }
    } 

How I used this method to retrive image from DB--> Add watermark--> Update to DB?I'm using Spring MVC.

My Photo Model class is :

public class Photo {
    @Id @GeneratedValue
    private int id;
    private int user_id;
    private String name;
    @Lob
    private Blob content;

invoke to get photo in Service Layer :

Photo photo = photoService.getPhotoById(50);

To update photo :

photoService.updatePhoto(photo);

Anyone please explain me to integrate this addTextWatermark() method in my project.

Answer 1

Five step process is what you need.

Step 1:

Read image (blob) from MySQL DB as byte[] using select query

Step 2:

Convert byte[] to BufferedImage like this

private BufferedImage createImageFromBytes(byte[] imageData) {
    ByteArrayInputStream bais = new ByteArrayInputStream(imageData);
    try {
        return ImageIO.read(bais);
    } catch (IOException e) {
        throw new RuntimeException(e);
    }
}

Step 3:

Change your addWaterMark method to produce Buffered Image with watermark

public static BufferedImage addTextWatermark(String text, BufferedImage sourceImage) {
 Graphics2D g2d = (Graphics2D) sourceImage.getGraphics();

 // initializes necessary graphic properties
 AlphaComposite alphaChannel = AlphaComposite.getInstance(AlphaComposite.SRC_OVER, 0.3f);
 g2d.setComposite(alphaChannel);
 g2d.setColor(Color.WHITE);
 g2d.setFont(new Font("Arial", Font.BOLD, 64));
 FontMetrics fontMetrics = g2d.getFontMetrics();
 Rectangle2D rect = fontMetrics.getStringBounds(text, g2d);

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

 // paints the textual watermark
 g2d.drawString(text, centerX, centerY);

 return sourceImage;
}

Step 4: Convert BufferedImage to byte[]

private byte[] createBytesFromImage(BufferedImage image) {
    try {
        ByteArrayOutputStream baos = new ByteArrayOutputStream();

        ImageIO.write(image,"png",baos);

        byte[] imageBytes = baos.toByteArray();
        baos.close();
        return imageBytes;

    } catch (IOException e) {
        throw new RuntimeException(e);
    }
}

Step 5:

Write this byte[] back to MySQL Db using update query.

Hope this helps.