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How to find anchor / pivot point in Java?

Ok, I'm trying to rotate the rectangle that is on top of the image. I have a Scrollable class that displays an image. I can draw Rectangles on top of the image. My problem is to rotate the rectangles while rotating the image. The rectangle is lost and placed in the wrong location.

I already tried to sue Graphics2D, AffineTransform, createTransformedShape (), but no luck.

Now I am trying to rotate the Rectangle manually. I am trying to get a Rectangle Point (x, y) using the following formula:

double rectX = (Math.cos(Math.toRadians(90)) * (x - anchorX) - Math.sin(Math.toRadians(90)) * (y - anchorY)) + anchorY;

double rectY = (Math.sin(Math.toRadians(90)) * (x - anchorX) - Math.cos(Math.toRadians(90)) * (y - anchorY)) + anchorY;

How to find anchorX and anchorY values ​​using Java? I tried immersing the image height by 2, but does not work for all rotation angles. Should I get the width and height of a JPanel or something else? Is there a formula that Java uses to find anchor points?

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2 answers

I'm not sure about the goal, but I see two possible alternative approaches:

  • Use the inverse transform as shown here .

  • Mark the vertical image and the rectangle in BufferedImageand rotate the composite image as shown.

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