java - java中MySqlDB中的图像添加水印

Question

在我的项目中，我尝试使用列(Blob)向 Mysql Db 表中的现有图像添加水印。

我使用下面的方法向任何图像文件添加水印，效果很好。

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);
        }
    } 

我如何使用此方法从数据库检索图像-->添加水印-->更新数据库？我正在使用Spring MVC。

我的照片模型类是:

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

在服务层调用获取照片:

Photo photo = photoService.getPhotoById(50);

更新照片:

photoService.updatePhoto(photo);

任何人请解释我如何将此 addTextWatermark() 方法集成到我的项目中。

Answer 1

五步流程正是您所需要的。

第 1 步:

使用选择查询从 MySQL DB 读取图像(blob)作为 byte[]

第 2 步:

像这样将 byte[] 转换为 BufferedImage

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

第 3 步:

更改 addWaterMark 方法以生成带水印的缓冲图像

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;
}

第 4 步:将 BufferedImage 转换为 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);
    }
}

第 5 步:

使用更新查询将此字节[]写回到MySQL Db。

希望这有帮助。