Get Pixel Color on screen Java?

问题

Hello I am trying to get the color of a particular pixel on my JFrame.

This is my code. My frame is red.

The problem I am having is when I click the Frame it should return me the RGB color for red that is (255,0,0) but when I click at different points i sometimes get the RGB color for white (255,255,255) what is the problem in my code guys?

public class guiTest extends JFrame 
{

    private static Shape ellipse;   
     private static Robot rb;

    public guiTest()
    {
    super("4-connected approach");
    setLayout(new FlowLayout());
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    setVisible(true);
    setSize(800,800);
    this.getContentPane().setBackground(Color.red);
    setLocationRelativeTo(null);
    addMouseListener(new MouseListener(){
        @Override
        public void mouseClicked(MouseEvent e) {
            System.out.println("Pixel:"+e.getX()+","+e.getY());             
            try {
                System.out.println(getPixel(e.getX(),e.getY()));
            } catch (AWTException e1) {
                // TODO Auto-generated catch block
                e1.printStackTrace();
            }

        }

        @Override
        public void mouseEntered(MouseEvent e) {
            // TODO Auto-generated method stub

        }

        @Override
        public void mouseExited(MouseEvent e) {
            // TODO Auto-generated method stub

        }

        @Override
        public void mousePressed(MouseEvent e) {
            // TODO Auto-generated method stub

        }

        @Override
        public void mouseReleased(MouseEvent e) {
            // TODO Auto-generated method stub

        }


    });

}


public static Color getPixel(int x,int y) throws AWTException{
    Robot rb=new Robot();
    return rb.getPixelColor(x, y);
}   


public static void main(String[] args){
    guiTest frame=new guiTest();    
}

回答1:

The problem is the way you are getting the coordinates - e.getX() and e.getY() -, because they are relative to the JFrame (the up-left corner of the JFrame is (0,0)).

To get the coordinates of the pixel, use:

public void mouseClicked(MouseEvent e) {
    Point p = e.getLocationOnScreen();

    System.out.println("Pixel:" + p.x + "," + p.y);
    try {
        System.out.println(getPixel(p.x, p.y));
    } catch (AWTException e1) {
        // TODO Auto-generated catch block
        e1.printStackTrace();
    }

}

[Extra] read this to improve other things: Why is my mouse lagging when I run this small mouse hook application?

来源：https://stackoverflow.com/questions/22217148/get-pixel-color-on-screen-java

标签

swing

colors

jframe

rgb

getpixel