问题
I'm struggling a bit trying to understand how to effectively use java image objects.
I have a very simple program which draws an image and then saves that image to the disk.
public class myBrain {
public static void main(String[] args) {
JFrame lv_frame = new JFrame();
lv_frame.setTitle("Drawing");
lv_frame.setSize(300, 300);
lv_frame.setDefaultCloseOperation(JInternalFrame.DISPOSE_ON_CLOSE);
lv_frame.add(new image());
lv_frame.setVisible(true);
}
}
class image extends JPanel {
public void paintComponent(Graphics graphic) {
super.paintComponent(graphic);
// draw image to gui
Graphics2D graphic2D = (Graphics2D) graphic;
graphic2D.fillArc(0, 0, 250, 250, 0, 90);
// save image to disk
BufferedImage image = new BufferedImage(250, 250, BufferedImage.TYPE_4BYTE_ABGR_PRE);
graphic2D = image.createGraphics();
graphic2D.fillArc(0, 0, 250, 250, 0, 90);
try {
File output = new File("file.png");
ImageIO.write(image, "png", output);
} catch(IOException log) {
System.out.println(log);
}
}
}
In the code there are two functions (I have written them in a single function for ease of understanding purposes). One to handle the gui and one to handle the saving.
The first one has it's Graphics2D object which it draws the arc to which is fine.
The second one needs a BufferedImage so that I can save it however when I try to create the graphic for the BufferedImage (image.createGraphics();) it overrides what I have drawn previously on the graphic2D which means I have to then draw it again (fillArc(0, 0, 250, 250, 0, 90);).
Is there a way around this so that I don't need to draw the image a second time to save it?
回答1:
You should start painting on your BufferedImage, retain it (as a class member for example), then in paintComponent method draw that BufferedImage (graphics2D.drawImage(...)).
The saving method should save the same BufferedImage.
来源：https://stackoverflow.com/questions/35702877/display-to-gui-and-save-to-disk-with-a-single-object-variable