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Basic steps for creating and saving an image as a file

On Java Studio » Java Knowledge

3,873 words with 2 Comments; publish: Sun, 23 Sep 2007 20:45:00 GMT; (15062.50, « »)

I have a good deal of experience with the Applet and Graphics2D class, having made a complete zoom/scroll map with it, but now I need to make some transparent png's with Java, and I've spent a lot of time looking both on Google and in these forums and I can't find any straightforward explanation of how to do it. All I want to do is:

-Create an empty, transparent image

-Draw some lines on it at angles which will make portions of it need to have alpha-level transparency

-Save it as a png

I would do this myself in Photshop, but I need it done precisely and several hundred times. Like I said, I know how to draw to a Graphics2D object, and I know about the paint method in the Applet class. However, I can't seem to figure out how to actually save an image file (especially a PNG), without doing some really convoluted and seemingly unecessary stuff with the Frame class and a bunch of other things. Can anyone help me, or direct me to the place that probably has already answered this?

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  • 2 Comments

    • Creating an image with an alpha channel is easy: use BufferedImage's

      constructor:BufferedImage(int width, int height, int type)

      and pass it a type like TYPE_INT_ARGB. To write an image, use the class

      ImageIO from javax.imagio. Demo:

      import java.awt.*;

      import java.awt.geom.*;

      import java.awt.image.*;

      import java.io.*;

      import javax.imageio.*;

      public class Satanic {

      public static void main(String[] args) throws IOException {

      int s = 300;

      BufferedImage image = new BufferedImage(s, s, BufferedImage.TYPE_INT_ARGB); //A!

      Graphics2D g = image.createGraphics();

      g.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);

      g.setPaint(Color.RED);

      g.translate(s/2, s/2);

      g.draw(createShape(s*4/10));

      g.dispose();

      ImageIO.write(image, "png", new File("temp.png"));

      }

      static Shape createShape(int r) {

      GeneralPath path = new GeneralPath();

      path.moveTo(0,-r);

      lineTo(path, r, -3*Math.PI/10);

      lineTo(path, r, 9*Math.PI/10);

      lineTo(path, r, Math.PI/10);

      lineTo(path, r, 13*Math.PI/10);

      path.closePath();

      path.append(new Ellipse2D.Float(-r, -r, 2*r, 2*r), false);

      return path;

      }

      static void lineTo(GeneralPath path, float r, double angle) {

      path.lineTo((float)(r*Math.cos(angle)), (float)(-r*Math.sin(angle)));

      }

      }

      For more tips, see this thread:

      http://forum.java.sun.com/thread.jspa?threadID=522483

      #1; Fri, 13 Jul 2007 02:44:00 GMT
    • Thank you so much, that was exactly what I needed.
      #2; Fri, 13 Jul 2007 02:44:00 GMT