How to Create a Pan and Zoom Image Viewer in WPF Using a Custom Control?

WPF image pan and zoom custom control

WPF provides a variety of methods to create a basic image viewer to achieve functions such as image panning, zooming, overlay display, and original image display. While built-in controls such as ViewBox and ImageBrush can assist with these functions, this article will guide you through custom code implementation to better understand how it works.

Customized ZoomBorder control

To handle panning and zooming, we will create a custom control called ZoomBorder. This class encapsulates the logic of image transformation.

ZoomBorder implementation

The

ZoomBorder control uses UIElement as a child element and applies transformations to achieve scaling and panning. The code defines event handlers for mouse wheel, left-button drag, and mouse movement to implement these functions.

Use

in MainWindow

In the MainWindow window, you can use ZoomBorder to display and manipulate images. The ZoomBorder attribute of Child should be set to the image you want to view.

Scaling algorithm

The scaling algorithm in the

child_MouseWheel event handler calculates the scaling factor based on the mouse wheel increment and applies it to the ScaleTransform of the image. It also adjusts the TranslateTransform to maintain the translation position relative to the mouse pointer.

Translation Algorithm

The

child_MouseLeftButtonDown and child_MouseMove event handlers handle panning. When the user left clicks and drags, the image's TranslateTransform updates to move the image accordingly.

Reset button implementation

To include a reset button, you add a button to MainWindow and handle its click event to call ZoomBorder's Reset method.

Summary

By implementing customization ZoomBorder in WPF, you can create a simple but efficient image viewer with pan and zoom functionality. This approach provides greater flexibility and control over the user experience than using predefined controls such as ViewBox.

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