AffineTransform and flipping the y-axis

Question

i ran into a strange problem when trying to flip the y-axis of a coordinate system that im creating:

   private AffineTransform getTransform() {
        if (transform == null) {
            transform = new AffineTransform();
            double scaleX = (double) this.getWidth() / (coordinateSystem.getMaxX() - coordinateSystem.getMinY());
            double scaleY = (double) this.getHeight() / (coordinateSystem.getMaxY() - coordinateSystem.getMinY());
            transform.setToScale(scaleX, scaleY);
            double deltaX = (coordinateSystem.getMaxX() - coordinateSystem.getMinX()) / 2;
            double deltaY = (coordinateSystem.getMaxY() - coordinateSystem.getMinY()) / 2;
            transform.translate(deltaX, deltaY);
        }
        return transform;
    }

The AffineTransform is set to scaling and translation. and everything works fine except that my y-values are inverted (max value is a the bottom of the coordinate system, min value is at the top). I tried switching this by inverting the scale factor for the y axis. but this was not working.

Do i have to let the Transform rotate by PI, to achieve the flipped y axis? Shouldn't multiplying the scale factor for the y axis by minus 1 be the same?

Answer 1

You have a typo on

double scaleX = (double) this.getWidth() / (coordinateSystem.getMaxX() - coordinateSystem.getMinY());

(Last Y should be an X .) Perhaps that's it.

Answer 2

PI旋转实际上根本不是一个正确的解决方案，因为它会翻转X轴和Y.