Re: [Geotools-gt2-users] Translate, Scale, Rotate

[Frank v. d. H. <dri...@gm...>]

Hi Greg,
Not a lot of information to go on, so some generalities...

If you're scaling the object (e.g. an icon or image) relative to map, you
need to translate the origin of the object to the origin of the map, then
rotate and scale, then translate to the correct location. Otherwise your
translation gets scaled and rotated.

And just to cover the obvious, I assume that your geoRotate is in degrees.
And in mathematical degrees (0 = X axis, CCW is +ve) as opposed to
geographical degrees (0 is the Y axis, clockwise is positive).

Frank


On Wed, Oct 8, 2014 at 4:08 PM, Greg Knight <gre...@gm...>
wrote:

> Greetings,
>
> I'm using v10.6 of GeoTools.  I am trying to do something that I think
> should be relatively simple -- but perhaps I dont understand matrices well
> enough.  I am trying to translate, scale,  and rotate a point.  Translation
> seems easy enough -- like I should be able to add the x and y offsets, then
> scale and rotate around that same offset.
>
> So Ive tried a number of things similar to this:
>
> final AffineTransform translateTransform =
>
>                     AffineTransform.getTranslateInstance(geoX, geoY);
>
>             final AffineTransform rotateTransform =
>
>
> AffineTransform.getRotateInstance(Math.toRadians(geoRotate), 0.0, 0.0);
>
>             final AffineTransform scaleTransform =
>
>                     AffineTransform.getScaleInstance(geoScale, geoScale);
>
> Then something like this:
>
>                     final Point2D sourcePoint = outerRing.get(j);
>
>
>
>                     // translate, rotate, scale
>
>                     final AffineTransform transform = new
> AffineTransform(translateTransform);
>
>                     transform.concatenate(rotateTransform);
>
>                     transform.concatenate(scaleTransform);
>
>
>
>                     final Point2D targetPoint = new Point2D();
>
>                     transform.transform(sourcePoint, targetPoint);
>
> For a source point of [ -95.75, 224.45 ]
>
>
> The correct transformation should result in  [ 716731.24, 3016405.92 ]
>
> Im getting [ 716942.89, 3016333.19 ]  which is in the neighborhood, but
> not really close enough.
>
> Where am I going wrong here?
>
> Thanks in advance!
>
> Greg
>
>
>
>
>
>
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