扩展BufferedImage

为什么以下代码显示黑色图像而不是图片？ 如何正确扩展BufferedImage？

class SizeOfImage { public static void main(String[] args) throws Exception { URL url = new URL("http://cloudbite.co.uk/wp-content/uploads/2011/03/google-chrome-logo-v1.jpg"); final BufferedImage bi = ImageIO.read(url); final String size = bi.getWidth() + "x" + bi.getHeight(); final CustomImg cstImg = new CustomImg(bi.getWidth(), bi.getHeight(), bi.getType()); SwingUtilities.invokeLater(new Runnable() { public void run() { JLabel l = new JLabel(size, new ImageIcon(cstImg), SwingConstants.RIGHT); JOptionPane.showMessageDialog(null, l); } }); } public static class CustomImg extends BufferedImage { public CustomImg(int width, int height, int type){ super(width, height, type); } } } 

Answer 1

 import java.awt.image.BufferedImage; import java.awt.Graphics; import javax.swing.*; import javax.imageio.ImageIO; import java.net.URL; class SizeOfImage { public static void main(String[] args) throws Exception { URL url = new URL( "http://cloudbite.co.uk/wp-content/" + "uploads/2011/03/google-chrome-logo-v1.jpg"); BufferedImage bi = ImageIO.read(url); final String size = bi.getWidth() + "x" + bi.getHeight(); final CustomImg cstImg = new CustomImg( bi.getWidth(), bi.getHeight(), bi. getType()); // paint something to the new image! Graphics g = cstImg.createGraphics(); g.drawImage(bi,0,0,null); g.dispose(); SwingUtilities.invokeLater(new Runnable() { public void run() { JLabel l = new JLabel( size, new ImageIcon(cstImg), SwingConstants.RIGHT ); JOptionPane.showMessageDialog(null, l); } }); } public static class CustomImg extends BufferedImage { public CustomImg(int width, int height, int type){ super(width, height, type); } } } 

Answer 2

可能是因为下载的图像bi从未被绘制到cstImg 。

这一行：

 CustomImg cstImg = new CustomImg(bi.getWidth(), bi.getHeight(), bi.getType()); 

根据bi的宽度，高度和类型创建新图像…而不是bi的内容。 为此你可能想要做类似的事情

 cstImg.getGraphics().drawImage(bi, 0, 0, null);