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How can I paint an image from BufferStrategy to Png file?

I've created a Java program that generates snowflakes and I'd like to save the image created as a .png file once the program finishes drawing.
I've searched on Internet, but I've found only programs using BufferedImage, while I use a BufferStrategy, so I don't know exactly where to start.
The draw method in my program uses a BufferStrategy to create the Graphics component.
For example, to draw a simple line the method is:
bs = display.getCanvas().getBufferStrategy();
if (bs == null) {
display.getCanvas().createBufferStrategy(3);
return;
}
g = bs.getDrawGraphics();
g.clearRect(0, 0, width, height);
g.setColor(Color.BLACK);
g.drawLine(0, 0, 50, 50);
What I would like is to get an exact copy of what has been drawn on the screen by the program to be saved as a .png image.
Hope you can help me.

Why not take a screenshot and then past it onto MS paint or some other(and better) image editing software like Photoshop or fire alpaca? That should solve your problem.

The common denominator between BufferedStrategy and BufferedImage is Graphics, so you want to write a paint routine so that you can simply pass a reference of Graphics to it
public void render(Graphics g) {
g.clearRect(0, 0, width, height);
g.setColor(Color.BLACK);
g.drawLine(0, 0, 50, 50);
}
Then you can pass what ever context you want.
BufferedImage img = new BufferedImage(width, height, BufferedImage.TYPE_RGB);
Graphics2D g2d = img.createGraphics();
render(g2d);
g2d.dispose();
Then you can use ImageIO.write to write the image to disk. See Writing/Saving an Image for more details

Black image when drawing Image on Canvas

I am working on a game in which I am use Canvas to display my graphics. I haven't (and don't plan on) using any Swing components...
In my render method:
I am using a BufferStrategy that I get from the canvas.
BufferStrategy bs = this.getBufferStrategy();
if(bs == null){
createBufferStrategy(3);
return;
}
Graphics g = bs.getDrawGraphics();
Later in the same method I end up drawing images(entities, trees, map, etc.), disposing of g, and showing the reference 'bs'.
...drawings onto canvas(entities, trees, map, etc.)
//END RENDER
g.dispose();
bs.show();
In between when I //END RENDER and finish drawing to g I ask if the game is paused. If so I am create a BufferedImage from what was made by g. I render that BufferedImage and then render my inventory screen on top of that:
BufferedImage img = new BufferedImage(this.width, this.height, BufferedImage.TYPE_3BYTE_BGR);
Graphics gx = img.getGraphics();
game.paint(gx);
g.drawImage(img, 0, 0, Color.CYAN, this);
interfaceLayer.render(g);
I am getting a black BufferedImage in my reference img.
Am I doing something wrong by using a BufferStrategy? Should I not be using two different Graphics objects?
Here is a picture of what it looks like before and after I pause the game to get an idea.
Instead of:
g.drawImage(img, 0, 0, Color.CYAN, this);
I changed it to:
g.drawImage(img, 20, 20, Color.CYAN, this);
Just some arbitrary x,y so you can get the idea of whats going on with they layering.
Dont mind the gray box. It is a fillRect() that I will eventually be expanding as part of the graphics in my inventory screen.
Why the black image?

Save a drawn picture on a JPanel in a file [java]

I've made a code to draw on a Jpanel
frame1.add( new JPanel() {
public void paintComponent( Graphics g ) {
super.paintComponent(g);
Graphics2D g2 = (Graphics2D)g;
g2.setColor(Color.white);
g2.fillRect(0, 0, width, height);
//Drawnig Part
});
Every thing is OK
Now My question is how to save what I've drawn on my JPanel in a file a.PNG or any other type
I have spent a lot of time to write the Drawing Part, So it will be helpful if you can suggest a solution by changing the required parts of my code, instead of rewriting the whole code.

I suggest that you buffer your drawing operations with a BufferedImage, like so:
// This should not be done in the draw method, but rather when
// the frame is created. You should also make a new buffer image when
// the frame is resized. `frameWidth` and `frameHeight` are the
// frame's dimensions.
BufferedImage bufferImage = new BufferedImage(frameWidth, frameHeight,
BufferedImage.TYPE_INT_ARGB);
Graphics2D bufferGraphics = bufferImage.createGraphics();
// In your draw method, do the following steps:
// 1. Clear the buffer:
bufferGraphics.clearRect(0, 0, width, height);
// 2. Draw things to bufferGraphics...
// 3. Copy the buffer:
g2.drawImage(bufferImage, null, 0, 0);
// When you want to save your image presented in the frame, call the following:
ImageIO.write(bufferImage, "png", new File("frameImage.png"));
The Java Tutorial on Creating and Drawing to an Image, along with the ImageIO API reference might be helpful should you require more information.

Have a look at Writing/Saving an Image for more details, but essentially you can do something like...
BufferedImage img = new BufferedImage(width, height, BufferedImage.TYPE_INT_ARGB);
Graphics2D g2d = img.createGraphics();
// Draw what ever you want to to the graphics context
g2d.dispose();
ImageIO.write(img, "png", new File("My Awesome Drawing.png"));
If you can't separate the drawing logic from your panel, you could simply use the Graphics context from the BufferedImage to paint the the component with.
Have a look at Exporting a JPanel to an image and Print the whole program layout for examples

Overlapping images with setIcon

I have made a JLabel where I display my images like this:
BufferedImage myimage;
imageLabel.setIcon(new ImageIcon(myimage));
Is it possible to draw an image and draw upon it a smaller image (an icon) with the setIcon command? How can I do it?
For example:
BufferedImage myimage1;
BufferedImage myLittleIcon;
imageLabel.setIcon(new ImageIcon(myimage1));
imageLabel.setIcon(new ImageIcon(myLittleIcon));
The above just draws the small icon.

Calling setIcon would overwrite the icon. However, you could try something like this:
// Assumed that these are non-null
BufferedImage bigIcon, smallIcon;
// Create a new image.
BufferedImage finalIcon = new BufferedImage(
bigIcon.getWidth(), bigIcon.getHeight(),
BufferedImage.TYPE_INT_ARGB)); // start transparent
// Get the graphics object. This is like the canvas you draw on.
Graphics g = finalIcon.getGraphics();
// Now we draw the images.
g.drawImage(bigIcon, 0, 0, null); // start at (0, 0)
g.drawImage(smallIcon, 10, 10, null); // start at (10, 10)
// Once we're done drawing on the Graphics object, we should
// call dispose() on it to free up memory.
g.dispose();
// Finally, convert to ImageIcon and apply.
imageLabel.setIcon(new ImageIcon(finalIcon));
This creates a new image, paints the big icon, and then paints the small icon.
You can also paint other things, like outlining a rectangle or filling an oval.
For more advanced graphics functions, try casting to a Graphics2D object.

Creating and rendering an image dynamically with transparent background for use with drawImage

Could someone provide an example of how to dynamically create an image in Java, draw lines et cetera on it, and then draw the image so that areas not painted will remain transparent in the drawing process?

One could use a BufferedImage with an image type that supports transparency such as BufferedImage.TYPE_INT_ARGB:
BufferedImage img = new BufferedImage(100, 100, BufferedImage.TYPE_INT_ARGB);
One can draw on the BufferedImage by calling BufferedImage.createGraphics to obtain a Graphics2D object, then perform some drawing:
BufferedImage img = new BufferedImage(100, 100, BufferedImage.TYPE_INT_ARGB);
Graphics2D g = img.createGraphics();
g.drawLine(0, 0, 10, 10); // draw a line.
g.dispose();
Then, since BufferedImage is a subclass of Image that can be used to draw onto another Image using one of the Graphics.drawImage that accepts an Image.