Re: Has working with raster graphics always been this complicated?
OK, I'm getting close, but I seem to be missing something. I've
included my code so far. I know it's a bit messy, but I'm still
learning to tighten up java code. This is a proof of concept for me.
It achieves something similar to what I wanted to do originally. I
currently have the program draw an oval (circle) where the mouse
clicks. That's enough to let me see what happens real-time.
Eventually, I'll have the reveal "expand" from the point where the
user clicks.
Anyway, drawing an expanding oval or box isn't the problem. This
example takes one image file (revealArea) and is supposed to overlay
it on another image file (baseImage). I expected to be able to click
in the window and wherever my mouse is, an oval will "paint a hole"
into the revealArea image, exposing part of the baseImage below.
I currently have the code of the revealArea image commented out. In
lieu of that image, I simply draw a white filled rectangle to
substitute. The rectangle overlays the base image fine (as witnessed
from the flicker). Drawing the oval does something unexpected. I set
the paint color to blue with an alpha of 30. I tried an alpha of zero,
expecting the hole to appear. When I click in the window, I get a
translucent blue circle blended with the white rectangle and not the
"hole" I expected to be formed. Is there a way to "paint" the hole?
Also, what techniques can I use to avoid the flicker of the images
drawing over one another?
Thanks!
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import java.applet.*;
import java.awt.*;
import java.awt.event.*;
import java.awt.image.*;
import java.lang.Math;
import javax.swing.*;
import javax.imageio.*;
import java.io.*;
public class Reveal extends Applet
implements MouseMotionListener {
int width, height;
int mx, my; // the mouse coordinates
Image baseImage;
Image revealArea;
Image backbuffer;
BufferedImage revealBuffer;
Graphics revealOverlay;
public void init() {
width = getSize().width;
height = getSize().height;
setBackground( Color.black );
mx = width/2;
my = height/2;
baseImage = getImage( getDocumentBase(), "baseimage.gif" );
revealArea = getImage( getDocumentBase(),"overlay.gif");
revealBuffer = new BufferedImage(100, 100,
BufferedImage.TYPE_INT_ARGB);
revealOverlay = revealBuffer.getGraphics();
revealOverlay.fillRect(10, 10, 80, 80);
//revealOverlay.drawImage(scratchArea, 0, 0, 100, 100, null);
repaint();
addMouseMotionListener( this );
}
public void mouseMoved( MouseEvent e ) {
repaint();
e.consume();
}
public void mouseDragged( MouseEvent e ) {
int x = e.getX();
int y = e.getY();
revealOverlay.setColor(new Color(0, 0, 255, 30));
revealOverlay.fillOval(x-5, y-5, 20, 20);
repaint();
e.consume();
}
public void paint( Graphics g ) {
g.drawImage(baseImage, 0, 0, null);
g.drawImage(revealBuffer, 0, 0, null);
}
}