如何将LONGBLOB图像从SQL转换为缓冲图像以显示在标签中

Question

我正在尝试从sql db中的longblob图像中显示字节数组，然后将其放入BufferedImage并将其缩放到标签的大小，我知道可以肯定的部分是我的SQL语句和实现后的重新缩放还有别的地方。 我不知道它是否实际上是在写入变量“图像”或被制成图标，然后是bufferedImage。 我肯定有一种方法可以使它从一开始就成为缓冲图像，但是我对Java的这一部分不太了解。 以下任何有用的见解是我的代码。

private void picPreviewerActionPerformed(java.awt.event.ActionEvent evt) {                                             
    // TODO add your handling code here:

        String vinNumber = vinInput.getText();


try{
Class.forName("com.mysql.jdbc.Driver");
Connection con = DriverManager.getConnection("jdbc:mysql://localhost:3306/newbieswithauctions","root","root");
PreparedStatement ps = con.prepareStatement("SELECT itemImage FROM images WHERE itemVin='"+ vinNumber + "'");

ResultSet rs = ps.executeQuery();    
    byte[] image = null;
    while(rs.next()){
         image = rs.getBytes("itemImage");
    }
Image img = Toolkit.getDefaultToolkit().createImage(image);
ImageIcon icon = new ImageIcon(img);
Image pic = icon.getImage();
BufferedImage bufferedPic =(BufferedImage) pic;
try{

     BufferedImage scaled = getScaledInstance(
     bufferedPic, picView.getWidth(), picView.getHeight(), RenderingHints.VALUE_INTERPOLATION_BILINEAR, true);
     picView.setIcon(new ImageIcon(scaled));
    }catch(Exception ex){

    }




}
catch(Exception ex)
{

}

}                                            

我已经修改了代码，并且我有这个按钮，它将打开一个带有图片的新表格，但是没有任何显示，这是按钮中的代码

  private void picPreviewerActionPerformed(java.awt.event.ActionEvent evt) {                                             
    // TODO add your handling code here:

    String vinNumber = vinInput.getText();


    try{
        Class.forName("com.mysql.jdbc.Driver");
        Connection con = DriverManager.getConnection("jdbc:mysql://localhost:3306/newbieswithauctions","root","root");
        PreparedStatement ps = con.prepareStatement("SELECT itemImage FROM images WHERE itemVin='"+ vinNumber + "'");

        ResultSet rs = ps.executeQuery();    
            byte[] image = null;
            while(rs.next()){
                 image = rs.getBytes("itemImage");
            }
        InputStream in = new ByteArrayInputStream(image);
        bufferedPic = ImageIO.read(in);
        ImageIO.write(bufferedPic, "png", new File("C:\\Users\\geluna\\Desktop\\Software Engineering\\NWAGUI-sqlpicsworks\\NWAGUI-sqlpicsworks\\images\\newImage.png"));


    }
    catch(Exception ex)
    {

    }
    new PicSearchWin().setVisible(true);
}  

并在形式上我在main方法中有这个，因此它在打开图片后立即填充图片，但是什么也没有发生，但是当我以该形式制作按钮并将代码放到那里时，按下按钮便可以使用。 看起来好糟糕 我希望它在窗体打开时执行。 有任何想法吗？

private void closeBtnActionPerformed(java.awt.event.ActionEvent evt) {                                         

    // TODO add your handling code here:
    this.dispose();
}                                        

private void btnActionPerformed(java.awt.event.ActionEvent evt) {                                    
    // TODO add your handling code here:
       try{
     BufferedImage NewBufferedPic = ImageIO.read(new File("C:\\Users\\geluna\\Desktop\\Software Engineering\\NWAGUI-sqlpicsworks\\NWAGUI-sqlpicsworks\\images\\newImage.png"));
     BufferedImage scaled = getScaledInstance(
     NewBufferedPic, pic.getWidth(), pic.getHeight(), RenderingHints.VALUE_INTERPOLATION_BILINEAR, true);
     pic.setIcon(new ImageIcon(scaled));
    }catch(Exception ex){
         JOptionPane.showMessageDialog(null,"GAY", "Error ", JOptionPane.ERROR_MESSAGE);
    }
}                                   





/**
 * @param args the command line arguments
 */
public static void main(String args[]) {
    /* Set the Nimbus look and feel */
    //<editor-fold defaultstate="collapsed" desc=" Look and feel setting code (optional) ">
    /* If Nimbus (introduced in Java SE 6) is not available, stay with the default look and feel.
     * For details see http://download.oracle.com/javase/tutorial/uiswing/lookandfeel/plaf.html 
     */
    try {
        for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
            if ("Nimbus".equals(info.getName())) {
                javax.swing.UIManager.setLookAndFeel(info.getClassName());
                break;
            }
        }
    } catch (ClassNotFoundException ex) {
        java.util.logging.Logger.getLogger(PicSearchWin.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
    } catch (InstantiationException ex) {
        java.util.logging.Logger.getLogger(PicSearchWin.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
    } catch (IllegalAccessException ex) {
        java.util.logging.Logger.getLogger(PicSearchWin.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
    } catch (javax.swing.UnsupportedLookAndFeelException ex) {
        java.util.logging.Logger.getLogger(PicSearchWin.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
    }
    //</editor-fold>

    /* Create and display the form */
    java.awt.EventQueue.invokeLater(new Runnable() {
        public void run() {
            new PicSearchWin().setVisible(true);

        }
    });
}

// Variables declaration - do not modify                     
private javax.swing.JButton btn;
private javax.swing.JButton closeBtn;
public static javax.swing.JLabel pic;
// End of variables declaration                   

}

Answer 1

为什么需要BufferedImage？
如果您存储了BLOB，请尝试以下操作：

Blob blob = rs.getBlob("itemImage"); 
byte[] bytes = blob.getBytes(1, (int) blob.length());
Image myImage = Toolkit.getDefaultToolkit().createImage(bytes);
Image scaled = createYourScaledInstance();
picView.setIcon(new ImageIcon(scaled));