Export JPanel Graphics to .png or .gif or .jpg

I'm trying to develop some sort of paint using Java.

I have a JComponent that is located inside of a JPanel.

I already can draw lines and rectangles into that JComponent.

Now, how can I export this drawings as an image (png, gif, jpg)?

I tried this:

BufferedImage b = new BufferedImage(1700,1100,BufferedImage.TYPE_INT_RGB);
this.print(getGraphics());
try{ImageIO.write(b,"png",new File("test.png"));}catch (Exception e) {}

But that only creates a .png file all black.

Help!!!

RESOLV开发者_C百科ED!!!

BufferedImage bi = new BufferedImage(this.getSize().width, this.getSize().height, BufferedImage.TYPE_INT_ARGB); 
Graphics g = bi.createGraphics();
this.paint(g);  //this == JComponent
g.dispose();
try{ImageIO.write(bi,"png",new File("test.png"));}catch (Exception e) {}

---

First of all, print() is the incorrect method. What I guess should work (haven't tested it yet) is: get the BufferedImage's Graphics (b.createGraphics()) and use that graphics object to paint() your panel/component.

(e.g. yourPanel.paint(b.createGraphics());)

---

this is a demo:

import javax.imageio.ImageIO;
import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.image.BufferedImage;
import java.io.File;
import java.util.ArrayList;
import java.util.List;

@SuppressWarnings("serial")
public class DrawGraph extends JPanel {
    private static final int PREF_W = 1000;
    private static final int PREF_H = 800;
    private static final int BORDER_GAP = 25;
    private static final int PADDING = 25;
    private static final Color GRAPH_COLOR = Color.green;
    private static final Color GRAPH_POINT_COLOR = new Color(100, 100, 100, 180);
    private static final Color GRID_COLOR = new Color(200, 200, 200, 200);
    private static final Stroke GRAPH_STROKE = new BasicStroke(3f);
    private static final int GRAPH_POINT_WIDTH = 4;
    private static final int Y_HATCH_CNT = 10;
    private List<Double> scores;

    public DrawGraph(List<Double> scores2) {
        this.scores = scores2;
    }

    @Override
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        Graphics2D g2 = (Graphics2D)g;
        g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);

        double xScale = ((double) getWidth() - (2 * BORDER_GAP)-PADDING) / (scores.size() - 1);
        double yScale = ((double) getHeight() - (2 * BORDER_GAP)-PADDING) / (getMaxScore() - getMinScore());

        List<Point> graphPoints = new ArrayList<Point>();
        for (int i = 0; i < scores.size(); i++) {
            int x1 = (int) (i * xScale + BORDER_GAP + PADDING);
            int y1 = (int) ((getMaxScore() - scores.get(i)) * yScale + BORDER_GAP);
            graphPoints.add(new Point(x1, y1));
        }

        g2.setColor(Color.WHITE);
        g2.fillRect(BORDER_GAP + PADDING, BORDER_GAP, getWidth() - (2 * BORDER_GAP) - PADDING, getHeight() - 2 * BORDER_GAP - PADDING);
        g2.setColor(Color.BLACK);

        g2.drawLine(BORDER_GAP + PADDING, getHeight() - BORDER_GAP - PADDING, BORDER_GAP + PADDING, BORDER_GAP);
        g2.drawLine(BORDER_GAP + PADDING, getHeight() - BORDER_GAP - PADDING, getWidth() - BORDER_GAP, getHeight() - BORDER_GAP - PADDING);

        for (int i = 0; i < Y_HATCH_CNT + 1; i++) {
            int x0 = BORDER_GAP + PADDING;
            int x1 = GRAPH_POINT_WIDTH + BORDER_GAP + PADDING;
            int y0 = getHeight() - ((i * (getHeight() - BORDER_GAP * 2 - PADDING)) / Y_HATCH_CNT + BORDER_GAP + PADDING);
            int y1 = y0;
            if (scores.size() > 0) {
                g2.setColor(GRID_COLOR);
                g2.drawLine(BORDER_GAP + PADDING + 1 + GRAPH_POINT_WIDTH, y0, getWidth() - BORDER_GAP, y1);
                g2.setColor(Color.BLACK);
                String yLabel = ((int) ((getMinScore() + (getMaxScore() - getMinScore()) * ((i * 1.0) / Y_HATCH_CNT)) * 100)) / 100.0 + "";
                FontMetrics metrics = g2.getFontMetrics();
                int labelWidth = metrics.stringWidth(yLabel);
                g2.drawString(yLabel, x0 - labelWidth - 5, y0 + (metrics.getHeight() / 2) - 3);
            }
            g2.drawLine(x0, y0, x1, y1);
        }

        for (int i = 0; i < scores.size(); i++) {
            if (scores.size() > 1) {
                int x0 = i * (getWidth() - BORDER_GAP * 2 - PADDING) / (scores.size() - 1) + BORDER_GAP + PADDING;
                int x1 = x0;
                int y0 = getHeight() - BORDER_GAP - PADDING;
                int y1 = y0 - GRAPH_POINT_WIDTH;
                if ((i % ((int) ((scores.size() / 20.0)) + 1)) == 0) {
                    g2.setColor(GRID_COLOR);
                    g2.drawLine(x0, getHeight() - BORDER_GAP - PADDING - 1 - GRAPH_POINT_WIDTH, x1, BORDER_GAP);
                    g2.setColor(Color.BLACK);
                    String xLabel = i + "";
                    FontMetrics metrics = g2.getFontMetrics();
                    int labelWidth = metrics.stringWidth(xLabel);
                    g2.drawString(xLabel, x0 - labelWidth / 2, y0 + metrics.getHeight() + 3);
                }
                g2.drawLine(x0, y0, x1, y1);
            }
        }

        Stroke oldStroke = g2.getStroke();
        g2.setColor(GRAPH_COLOR);
        g2.setStroke(GRAPH_STROKE);
        for (int i = 0; i < graphPoints.size() - 1; i++) {
            int x1 = graphPoints.get(i).x;
            int y1 = graphPoints.get(i).y;
            int x2 = graphPoints.get(i + 1).x;
            int y2 = graphPoints.get(i + 1).y;
            g2.drawLine(x1, y1, x2, y2);
        }

        g2.setStroke(oldStroke);
        g2.setColor(GRAPH_POINT_COLOR);
        for (int i = 0; i < graphPoints.size(); i++) {
            int x = graphPoints.get(i).x - GRAPH_POINT_WIDTH / 2;
            int y = graphPoints.get(i).y - GRAPH_POINT_WIDTH / 2;;
            int ovalW = GRAPH_POINT_WIDTH;
            int ovalH = GRAPH_POINT_WIDTH;
            g2.fillOval(x, y, ovalW, ovalH);
        }
    }

    @Override
    public Dimension getPreferredSize() {
        return new Dimension(PREF_W, PREF_H);
    }

    private double getMinScore() {
        double minScore = Double.MAX_VALUE;
        for (Double score : scores) {
            minScore = Math.min(minScore, score);
        }
        return minScore;
    }

    private double getMaxScore() {
        double maxScore = Double.MIN_VALUE;
        for (Double score : scores) {
            maxScore = Math.max(maxScore, score);
        }
        return maxScore;
    }

    public static void createAndShowGui(ArrayList<Double> scores, String s) {
        DrawGraph mainPanel = new DrawGraph(scores);

        JFrame frame = new JFrame(s);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.getContentPane().add(mainPanel);
        frame.getContentPane().add(new JButton(new AbstractAction("Save Image") {
            @Override
            public void actionPerformed(ActionEvent e) {
                mainPanel.saveImage(new File("graph.png"));
            }
        }),BorderLayout.SOUTH);
        frame.pack();
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
    }

    public void saveImage(File file){
        BufferedImage bi = new BufferedImage(this.getSize().width, this.getSize().height, BufferedImage.TYPE_INT_ARGB);
        Graphics g = bi.createGraphics();
        this.paint(g);
        g.dispose();
        try{
            ImageIO.write(bi,"png",file);
        }catch (Exception e) {
            e.printStackTrace();
        }
    }

    public static void main(String args[]) {
        final ArrayList<Double> inputValues = new ArrayList<Double>();
        inputValues.add(1d);
        inputValues.add(2d);
        // Read input values from text document and store in ArrayList
        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                DrawGraph.createAndShowGui(inputValues, "MyGraphTitle");
            }
        });
    }
}

you can change it by youself.