Draw a circle on a PNG file in Java

Asked Jan 22 '16 at 21:11

Active Jan 22 '16 at 21:38

Viewed 333 times

I am trying to read a PNG, draw a circle and write the image to the same or a different file. But the new image is identical to the input image. What am I missing? Thank you.

File file = new File("Screenshot.png");
BufferedImage image = ImageIO.read(file);

Graphics2D g2d = image.createGraphics();
g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
g2d.setColor(Color.RED);
g2d.fillOval(center.x - radius, center.y - radius, radius * 2, radius * 2);
g2d.dispose();

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

EDIT: I did find that linked question myself, but still do not understand how to modify the image I read from file using ImageIO. The example from the answer showing there is creating a BufferedImage from the JPanel.

edited Jan 22 '16 at 21:38

asked Jan 22 '16 at 21:11

derrdji

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Is image being modified? I just see it reading, then writing out but no modifying. – Eric G Jan 22 '16 at 21:15
you are drawing your circle on a separate image. So when you save the first image back it's unmodified. Is this a mistake? – ControlAltDel Jan 22 '16 at 21:15
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Is `screenshotImage` supposed to be `image` on line 4? – Eric G Jan 22 '16 at 21:15
@Eric G, yes it was a mistake. fixed. – derrdji Jan 22 '16 at 21:17
Draw the image to the `Graphics2D` before you draw your circle, and then save the `Graphics2D` (not the original *image*). – Elliott Frisch Jan 22 '16 at 21:20
2

Have you tried printing the values of `center` and `radius` to make sure they're valid and within the size of the image? – VGR Jan 22 '16 at 21:21
Is the `g2d.dispose()` causing the changes to be removed before it gets written? – Eric G Jan 22 '16 at 21:22
@ElliottFrisch, how do I save the `Graphics2D` to a new image? – derrdji Jan 22 '16 at 21:40
@VGR, thank you! I was calling it in a test with a very large screenshot image, and a very small radius. – derrdji Jan 22 '16 at 21:47

Draw a circle on a PNG file in Java

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