Get/Calculate the correct size of a Control after Render/Layouttransform was applied

Question

I'm trying to get the size (width/height) of an Image control after I applied a Transform to it (either Render- or Layouttransform, doesn't matter in this case).

My Image control is embedded in a ScrollViewer. I'm using the Layout/Rendertransform to zoom the image which does work, but the ActualWidth/ActualHeight or RenderSize properties don't show me the new height/width. I tried calling InvalidateMeasure()and UpdateLayout() on the Image control without success.

This is my current code to zoom the image to the height:

double imageHeight = imageBox.ActualHeight;
double containerHeight = (imageBox.Parent as ScrollViewer).ActualHeight;
double facHeight = containerHeight / imageHeight;

var scaleTransform = imageBox.LayoutTransform.Value; //imageBox.RenderTransform.Value;
scaleTransform.ScalePrepend(facHeight, facHeight);

MatrixTransform newTransform = new MatrixTransform(scaleTransform);
imageBox.LayoutTransform = newTransform;

On first execution of that method the image will be (more or less) correctly zoomed. In this case, I want the image vertically fully shown, regardless of it's width, so that I only have a horizontal scrollbar (or no scrollbar at all if imageHeight > imageWidth).

On second execution, it'll zoom in again because imageBox.ActualHeight didn't change.

I tried various combinations of InvalidateMeasure and UpdateLayout but that didn't help.

See [this](http://stackoverflow.com/questions/1169589/wpf-can-i-get-the-size-of-a-uielement-after-a-transform-is-applied) — Fᴀʀʜᴀɴ Aɴᴀᴍ, Nov 23 '15 at 11:49
@FarhanAnam the problem is that they're using ScaleTransform. For some reason my Image control only returns a MatrixTransform. — Steffen Winkler, Nov 23 '15 at 12:06

score 3 · Accepted Answer · answered Nov 23 '15 at 11:51

3

For the transformed size after LayoutTransform (but not RenderTransform) was applied, check the Image control's DesiredSize property:

double imageHeight = imageBox.DesiredSize.Height;

answered Nov 23 '15 at 11:51

Clemens

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Get/Calculate the correct size of a Control after Render/Layouttransform was applied

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