colorpan.java

learning java的源代码。书中每个实例都有相关的代码example。

//file: ColorPan.java
import java.awt.*;
import java.awt.event.*;
import java.awt.image.*;
import javax.swing.*;

public class ColorPan extends JComponent {
  BufferedImage image;

  public void initialize(  ) {
    int width = getSize(  ).width;
    int height = getSize(  ).height;
    int[] data = new int [width * height];
    int i = 0;
    for (int y = 0; y < height; y++) {
      int red = (y * 255) / (height - 1);
      for (int x = 0; x < width; x++) {
        int green = (x * 255) / (width - 1);
        int blue = 128;
        data[i++] = (red << 16) | (green << 8 ) | blue;
      }
    }

    image = new BufferedImage(width, height,
        BufferedImage.TYPE_INT_RGB);
    image.setRGB(0, 0, width, height, data, 0, width);
  }

  public void paint(Graphics g) {
    if (image == null) initialize(  );
    g.drawImage(image, 0, 0, this);
  }

  public static void main(String[] args) {
    JFrame f = new JFrame("ColorPan");
    f.getContentPane().add(new ColorPan(  ));
    f.setSize(300, 300);
    f.setLocation(100, 100);
    f.addWindowListener(new WindowAdapter(  ) {
      public void windowClosing(WindowEvent e) {
        System.exit(0);
      }
    });
    f.setVisible(true);
  }
}