can't get my coordinates graphics2D mouseclick java

Question

I got an extended JLabel class where I draw my Map using the code below : the new AffineTransform() is the identity to left my image as it is (0,0,w,h)

 mygraphics2D = (Graphics2D) getGraphics();
 graphics2D.scale(2.0,2.0) ;
 graphics2D.rotate(....
 graphics2D.drawImage(myImageIcon.getImage(),new AffineTransform(), this);

now when I click on my JLabel using this event :

public void mouseClicked(MouseEvent e) {
x =e.getX() ;
y = e.getY();
NewX = ????
NewY = ????
}

I want to retrieve my new coordinates "the scaled,rotated ... coords" I tried

Point2D ptSrc = new Point2D.Double(x, y);
Point2D ptDst = new Point2D.Double(0, 0);
mygraphics2D.getTransform().transform(ptSrc, ptDst);

but the ptDst is different from the (scaled,rotated,..) coordinates, any help please !!!

*I want to retrieve my new coordinates "the scaled,rotated ... coords"* Why? What relevance are they, or the scaling/rotation? What is the feature this is supposed to implement? — Andrew Thompson, Aug 06 '12 at 00:47
I have a map that can be transformed (scale, rotates, translate), & I want to add objects by clicking on the `JLabel` so the new object will be located at the new coords — S3ddi9, Aug 06 '12 at 00:50
I think AndrewThompson is right. Do you *really* need to apply the transform when you click or can you just let the paint process take care of it for you? — MadProgrammer, Aug 06 '12 at 00:51
For better help sooner, post an SSCCE. Even as code snippets go, those are not very instructive. *"I have a map that can be transformed (scale, rotates, translate)"* Since the image is not transformed in any way, it makes me wonder.. What part of the map **is** transformed? — Andrew Thompson, Aug 06 '12 at 00:54
my map is `myImageIcon.getImage()` when i scale for example the coords changes of course, when i click on a specific region of the image i want to add my object there — S3ddi9, Aug 06 '12 at 00:57
a) That was as clear as mud. b) Now that two people have made comments, you need to prefix a comment with @MadProgrammer (or other name) to ensure the person is notified of the comment. — Andrew Thompson, Aug 06 '12 at 01:16
@SéddikLaraba Are you *sure* `ptDst` doesn't contain the scaled/rotated point? `final Point transformed = graphics.getTransform().transform(e.getPoint(), null);` — obataku, Aug 06 '12 at 01:28
@SéddikLaraba yes, sorry, I'm an idiot. I didn't quite realize what you were asking for :p — obataku, Aug 06 '12 at 02:00

score 4 · Accepted Answer · edited May 23 '17 at 11:55

4

It sounds like you need both a forward and inverse transform to translate between the two co-ordinate systems. In this example, the scaling equations are explicit; in this alternate approach, a second AffineTransform is used.

edited May 23 '17 at 11:55

Community

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answered Aug 06 '12 at 02:14

trashgod

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that's exactly what I wanted, retrieve mouse coords from a scaled JPanel, I don't get why none understood that, even if its blod written ???, thank you @trashgod – S3ddi9 Aug 06 '12 at 02:25
You're welcome. Credit to commenters for elucidation and to @finw for a working example; many references merely suggest that it's possible. – trashgod Aug 06 '12 at 02:33

score 1 · Answer 2 · edited Aug 06 '12 at 02:34

1

I found these:

Don't know if they will help or not.

edited Aug 06 '12 at 02:34

trashgod

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28
229
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answered Aug 06 '12 at 01:21

MadProgrammer

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score 1 · Answer 3 · answered Sep 22 '13 at 12:23

Its not so hard ;-)

When you repaint the Component save the AffineTransform after the transforming with g2.getTransform()
Then call the function invert() on it

In the mouseClicked() event us the following code:

Point2D p= trans.transform(new Point2D.Double(evt.getX(), evt.getY()), null);
System.out.println("click x="+p.getX()+" y="+p.getY());

Thats it!

can't get my coordinates graphics2D mouseclick java

3 Answers3

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