I am trying to save the main viewport and JScrollPane headers (larger than the screen) to PNG image files. I created 3 classes extending the JPanel (MainTablePanel, MapsHeaderPanel and ItemsHeaderPanel) and set them in viewports. Each of them has this method:
public BufferedImage createImage() { BufferedImage bi = new BufferedImage(getSize().width, getSize().height, BufferedImage.TYPE_INT_ARGB); Graphics g = bi.createGraphics(); paint(g); g.dispose(); return bi; }
Each class also has a drawing method that draws the background and then calls super.paint () to draw some label. For instance:
public void paint(Graphics g){ g.setColor(Color.BLACK); g.fillRect(0, 0, getWidth(), getHeight()); g.setColor(new Color(255, 255, 0, 50)); // for loop that paints some vertical yellow lines for(int i=0; i<getWidth(); i+=K.mW){ g.fillRect(i-1, 0, 2, getHeight()); if(i%(K.mW*5)==0){ g.fillRect(i-2, 0, 4, getHeight()); } } // called to pain some rotated JLabels super.paint(g); }
From an external JFrame, I tried to save them in a PNG file using this code:
BufferedImage tableImg = mainTableP.createImage(); BufferedImage topImg = mapsHeaderP.createImage(); BufferedImage leftImg = itemsHeaderP.createImage(); ImageIO.write(tableImg, "png", new File(s.homeDir+"/table.png")); ImageIO.write(topImg, "png", new File(s.homeDir+"/top.png")); ImageIO.write(leftImg, "png", new File(s.homeDir+"/left.png"));
This is a screenshot of the application launch: screenshot
And this is the exported header: top
If I comment on the instruction "super.paint (g)", I get the correct image (thus, without all JLables, of course). It looks like the second paint (super.paint (g)) is colored, offset in BufferedImage, and accepting elements outside its JPanel. Can anyone explain this behavior to me? Thanks.
========== EDIT for SSCCE ====================================== ========================================= ==
This should compile. You can execute it as is, and in c: \ you will find two images (top.png and left.png) that should match both headers. Unfortunately, this is not the case. The background is not painted. Moreover (especially if you look at left.png) you can see that the labels are drawn twice and shifted (note, for example, “Left test 21”).
import java.awt.*; import java.awt.image.BufferedImage; import java.io.File; import javax.imageio.ImageIO; import javax.swing.*; public class Main { public static void main(String[] args) { JFrame frame = new JFrame(); frame.setLayout(null); frame.setSize(800, 600); JScrollPane scrollP = new JScrollPane(); scrollP.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_ALWAYS); scrollP.setHorizontalScrollBarPolicy(JScrollPane.HORIZONTAL_SCROLLBAR_ALWAYS); MyPanel top = new MyPanel(); for(int i=0; i<30; i++){ JLabel label = new JLabel("Test "+i); label.setOpaque(false); label.setBounds(50*i, 40, 50, 20); label.setForeground(Color.GREEN); top.add(label); } top.setLayout(null); top.setOpaque(false); top.setPreferredSize(new Dimension(50*30, 200)); top.validate(); MyPanel left = new MyPanel(); for(int i=0; i<30; i++){ JLabel label = new JLabel("Left test "+i); label.setBounds(0, 50*i, 100, 20); label.setForeground(Color.RED); left.add(label); } left.setLayout(null); left.setOpaque(false); left.setPreferredSize(new Dimension(200, 50*30)); MyPanel center = new MyPanel(); center.setLayout(null); center.setOpaque(false); center.setPreferredSize(new Dimension(50*30, 50*30)); scrollP.setViewportView(center); scrollP.setColumnHeaderView(top); scrollP.setRowHeaderView(left); scrollP.setBounds(0, 50, 750, 500); frame.add(scrollP); frame.setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE); frame.setVisible(true); try{ BufferedImage topImg = top.createImage(); ImageIO.write(topImg, "png", new File("C:/top.png")); BufferedImage leftImg = left.createImage(); ImageIO.write(leftImg, "png", new File("C:/left.png")); }catch(Exception e){ e.printStackTrace(); } } } class MyPanel extends JPanel{ public void paint(Graphics g){ g.setColor(Color.BLACK); g.fillRect(0, 0, getWidth(), getHeight()); g.setColor(new Color(255, 255, 0, 50)); for(int i=0; i<getWidth(); i+=50){ g.fillRect(i-1, 0, 2, getHeight()); } super.paint(g);