How can I prevent WPF from trimming my image?

Question

I am writing a WPF application that displays an image that is initially centered. The user can enlarge / reduce the image and move the image, which is implemented using ScaleTransform and TranslateTransform . This works great.

The problem is that the image is much larger than the window, and the user moves the image or scales enough to make the whole image visible. The part of the image that was originally hidden is not displayed, and instead only the originally viewed part of the image is drawn.

Based on some other questions , if I put my image inside a Canvas which will cause the whole image to display, and when moving it will display correctly. The problem is that I don’t want my image to be in Canvas , since this prevents any other layout from appearing - the HorizontalAlignment and VerticalAlignment properties are ignored (so the image is no longer centered), and I need to implement an option that will make the image as possible large to fill the entire area of ​​the window that no longer works (setting the Stretch property to UniformToFill does nothing).

Currently, two transforms have the RenderTransform property RenderTransform . If I use LayoutTransform , the entire image will be drawn, but it will also not allow the user to move any part of the image from the edge of the window (this is the behavior I would like to preserve).

How can I say that WPF always displays the whole image without using Canvas or LayoutTransform ?

Answer 1

I suggest not using TranslateTransform, but rather relying on ScrollViewer instead.

 <ScrollViewer> <Grid> <Image Source="blabla"> <Image.LayoutTransform> <ScaleTransform /> </Image.LayoutTransform> </Image> </Grid> </ScrollViewer> 

ScrollViewer provides unlimited image space for expansion, the entire image will be displayed. The grid creates a centered layout while keeping the image expand. If you don’t like the scroll bars for managing translation, you can hide them and flip your own solution.

LayoutTransform is definitely a transition method, so the actual size of the image in pixels (based on scaling) is properly reflected in your window.