Ok I've simplified the above scaling fix quite a bit. I make no claims of
being a Math expert...
if (originalMapViewport.isMatchingAspectRatio()) {
double aspectRatioScaling = originalMapViewport.getBounds().getWidth()
* scaleFactor / originalMapViewport.getBounds().getHeight();
scaleFactor = aspectRatioScaling;
}
env.translate(delta.x * scaleFactor, delta.y * scaleFactor);
This works quite well. However I've noticed that both this and the previous
implementation has an issue when the screen width is very wide. For example
if the aspectRatioScaling value becomes > 1 then the zooming in behaviour
actually becomes zooms out.
At this point I'm just talking to myself, but if anyone has ideas feel free
to join in.
On Fri Nov 14 2014 at 10:22:16 AM Leif Gruenwoldt <lei...@gmail.com> wrote:
> I found a way to calculate the scale factor that the envelop I get back is
> (vs. requested). Maybe this is a total kluge and there is a better way?
>
> I added this to the above implementation:
>
> MapViewport originalMapViewport =
> mme.getSource().getMapContent().getViewport();
> ReferencedEnvelope envNoScale =
> mme.getEnvelopeByWorld(originalMapViewport.getBounds().getWidth());
> double actualScale = envNoScale.getHeight() * scaleFactor /
> originalMapViewport.getBounds().getHeight();
> env.translate(delta.x * actualScale, delta.y * actualScale);
>
> One thing I'm not certain about is why calculating the actualScale value
> with getHeight works but getWidth doesn't?
>
> Anyhow I hope to tidy this up and submit a pull request in the near
> future. I'm going to propose that having a Google Maps style mouse wheel
> zoom as the default in JMapFrame would be a good thing!
>
>
>
>
>
> On Thu Nov 13 2014 at 11:35:00 AM Leif Gruenwoldt <lei...@gmail.com>
> wrote:
>
>> I'm trying to create a mouse wheel zoom behavior similar to Google Maps
>> for my JMapPanel. I started with the sample code that is documented here:
>>
>> http://docs.geotools.org/stable/userguide/unsupported/
>> swing/jmappane.html#actions
>>
>> I want to improve that example such that the zoom focuses and follows the
>> mouse cursor position -- like Google Maps.
>>
>> My implementation has an issue though with what seems to be a scaling
>> problem of the MapViewport. I request a specific Envelop width, but get a
>> different width. The behaviour I'm observing sounds exactly like what's
>> documented here:
>>
>> http://docs.geotools.org/stable/userguide/unsupported/
>> swing/jmappane.html#how-map-position-and-scale-are-calculated
>>
>> Specifically I have a window of size 1280x720 pixels (minus the map
>> layers side panel) and I request a new Envelope of width scaled by 0.5, but
>> then get one that has been scaled only by ~0.8. How can I programatically
>> determine the scale I'm going to get when the envelope is passed to
>> MapPane#setDisplayArea? I need this value because I use it to scale how
>> much envelope needs to be translated to "follow" the the cursor. I don't
>> quite understand if or how the MapViewPort#getScreenToWorld or
>> getWorldToScreen AffineTransform's can help? The value I was getting from
>> the AffineTransform#scaleX didn't seem to line up with the 0.8 that I was
>> seeing in my particular case.
>>
>> Please view my code below. Notice that I use a different scaleFactor for
>> translating the envelope. This is the problem, because it falls on it's
>> face as soon as I resize the window. Thoughts?
>>
>> P.S. Once I get this sorted out I hope to turn it into a pull request so
>> everyone can benefit.
>>
>> @Override
>> public void onMouseWheelMoved(MapMouseEvent mme) {
>> int clicks = mme.getWheelAmount();
>> double scaleFactor = (clicks < 0 ? 0.5 : 2); // half or double size
>>
>> DirectPosition2D mouseOriginalPixels = mme.getWorldPos();
>> ReferencedEnvelope origEnv = mapFrame.getMapPane().getDisplayArea();
>> DirectPosition2D centerOriginal = new
>> DirectPosition2D(origEnv.getMedian(0),
>> origEnv.getMedian(1));
>> DirectPosition2D delta = new DirectPosition2D(centerOriginal.x -
>> mouseOriginalPixels.x, centerOriginal.y - mouseOriginalPixels.y);
>>
>> ReferencedEnvelope env = mme.getEnvelopeByWorld(mme.
>> getSource().getDisplayArea().getSpan(0) * scaleFactor);
>> scaleFactor = clicks < 0 ? 0.804 : 3.219; // FIXME this hack only
>> works until we resize the window!
>> env.translate(delta.x * scaleFactor, delta.y * scaleFactor);
>> mapFrame.getMapPane().setDisplayArea(env);
>> }
>>
>
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