java - Mysql blob 图片转换为 awt.image，然后 awt.image 转换为 blob，无需更改大小

Question

我目前正在开发一个 Swing 程序，我将图片作为 blob 存储在 mysql 数据库中。由于此处描述的原因太长，我有时必须将之前从数据库加载的图片保存回数据库中。

下面是我当前如何在 java 中从数据库加载/保存到数据库的示例代码:

package oldutils;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.awt.image.RenderedImage;
import java.io.*;
import java.sql.*;
import javax.imageio.ImageIO;
import javax.swing.*;
import utils.SingletonConnection;

public class DisplayImage2 extends JFrame
{
private Connection        connection = null;
private ResultSet         result     = null;
private PreparedStatement statement  = null;
private Blob              blob       = null;
private ImageIcon         imageIcon  = null;
private JLabel            labelPhoto = null;
private Image             image      = null;
private String            query      = null;
private byte[]            byteArray  = null;

public DisplayImage2()
    {
        super("Image Display");
        setSize(600, 600);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        connection = SingletonConnection.getConnection();
        try
            {
                query = "SELECT * FROM photo WHERE pkPhoto=?";
                statement = connection.prepareStatement(query);
                statement.setInt(1, 61);
                result = statement.executeQuery();

                while ( result.next() )
                    {
                        byteArray = result.getBytes("photoImage");
                        image = Toolkit.getDefaultToolkit().createImage(byteArray);
                        imageIcon = new ImageIcon(image);
                    }

                labelPhoto = new JLabel();
                labelPhoto.setIcon(imageIcon);
                add(labelPhoto);
                setVisible(true);

                try
                    {
                        BufferedImage bufferedImage = new BufferedImage(image.getWidth(null), 
                                    image.getHeight(null), BufferedImage.TYPE_INT_RGB);
                        Graphics2D bImageGraphics = bufferedImage.createGraphics(); // Obtain graphics
                        bImageGraphics.drawImage(image, null, null); //Draw Image into BufferedImage
                        RenderedImage rImage = (RenderedImage) bufferedImage; // Cast to rendered image
                        ByteArrayOutputStream bas = new ByteArrayOutputStream();
                        ImageIO.write(rImage, "png", bas);
                        byteArray = bas.toByteArray();
                        blob = new javax.sql.rowset.serial.SerialBlob(byteArray);
                    }
                catch (IOException e)
                    {
                        e.printStackTrace();
                    }

                query = "INSERT INTO photo (photoName, photoImage) VALUES(?,?)";
                statement = connection.prepareStatement(query);
                statement.setString(1, "Image Test");
                statement.setBlob(2, blob);
                statement.executeUpdate();
            }
        catch (SQLException e)
            {
                e.printStackTrace();
            }
    }

public static void main(String[] args)
    {
        new DisplayImage2();
    }
  }

问题在于，在首先将图片插入表中之前，首先将图片的压缩率/大小/质量仔细“制作”为 JPEG 图片。但是使用上面代码中的方法，使用 ImageIO.write()，我被迫在重新保存图片时增大图片的原始大小(例如“PNG”)或缩小图片(例如“JPG”)并丢失质量。有没有办法将图像位从数据库获取到内存，使用它们，然后将它们作为原始 blob 返回到数据库，而不改变大小或质量？

Answer 1

Leo 在他的评论中回答了这个问题，但由于他如此谦虚地否认投票点，所以我自己写它，以便它可以帮助某人......

所需要做的就是(假设 byteArray 仍在内存中)跳过所有 ImageBuffer/Graphics/.. 创建和操作部分，重用相同的 ByteArray[] 并像以前一样简单地获取一个 blob，然后保存它。

public DisplayImage2()
{
super("Image Display");
setSize(600, 600);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
connection = SingletonConnection.getConnection();
// LOAD FROM BLOB
try
    {
        query = "SELECT * FROM photo WHERE pkPhoto=?";
        statement = connection.prepareStatement(query);
        statement.setInt(1, 61);
        result = statement.executeQuery();

        while ( result.next() )
            {
                byteArray = result.getBytes("photoImage");
                image = Toolkit.getDefaultToolkit().createImage(byteArray);
                imageIcon = new ImageIcon(image);
            }

        labelPhoto = new JLabel();
        labelPhoto.setIcon(imageIcon);
        add(labelPhoto);
        setVisible(true);
        // SAVE TO BLOB

        blob = new javax.sql.rowset.serial.SerialBlob(byteArray);

        query = "INSERT INTO photo (photoName, photoImage) VALUES(?,?)";
        statement = connection.prepareStatement(query);
        statement.setString(1, "Image Test");
        statement.setBlob(2, blob);
        statement.executeUpdate();
    }

catch (IOException e)
    {
        e.printStackTrace();
    }
catch (SQLException e)
    {
        e.printStackTrace();
    }
}