CODEWITHSUNDEEP
javagraphics
user1265486
user1265486

Reputation:

Drawing a part of an image (Java)

Here's my problem- I'm trying to draw a circular part of a single image.

I'm doing some work on a top-down dungeon crawler sort of game, and I'm attempting to make a light radius around the player. The floor is a single image, and I need to draw only a small, circular part of it. I've been looking at this method:

drawImage(Image img,
          int dx1, 
          int dy1,
          int dx2,
          int dy2,
          int sx1,
          int sy1,
          int sx2,
          int sy2,
          Color bgcolor, 
          ImageObserver observer)

But, that looks like it would only draw a square subsection. Does anyone happen to know an easier method than drawing tons of little squares to give the illusion of a circle?

Thanks

Upvotes: 1

Views: 4401

Answers (3)

Jon Egeland
Jon Egeland

Reputation: 12613

You can do this with the setClip() method in Graphics.

It needs some other work, but:

import java.awt.Graphics;
import java.awt.geom.QuadCurve2D;
//...

  g.setClip(new QuadCurve()); // Set the bounding curve for the image.
  g.drawImage(...);

As I said, it needs more work, meaning the QuadCurve2D object might need to be defined differently, but you can check the doc for that.

Upvotes: 2

Wouter Lievens
Wouter Lievens

Reputation: 4019

The neatest effect for a light radius would be to use an overlay with a gradient in its alpha channel.

Something like this:

// do this once during setup
overlay = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGBA);
for (int x = 0; x < width; ++x)
{
    for (int y = 0; y < height; ++y)
    {
        double range = 100;
        double distance = Math.sqrt(Math.pow(x - width / 2, 2) + Math.pow(y - height / 2, 2));
        int value = Math.max(100, (int)Math.round(255 - 100 * distance / range));
        overlay.setRGB(x, y, new Color(0, 0, 0, value));
    }
}
....
// do this every frame
gfx.drawImage(overlay, 0, 0, null);

I did not compile this so it's probably full of errors!

If you want some "flicker" in it you can generate several maps, and add some noise to the alpha values. Or even tune the colors so you get warmer light.

Upvotes: 1

amc6
amc6

Reputation: 273

This isn't a great solution, but what if you drew the entire floor, then a black image with a transparent hole in its center?

Upvotes: 0

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