How to Correctly Zoom and Translate an Image from the Mouse Location?

Zooming and Translating an Image from the Mouse Location

When attempting to zoom and translate an image from the mouse location, it's crucial to consider the order in which transformations are applied to achieve the desired result. Here are some suggestions and techniques to rectify the issue:

• Transformation Division: Separate distinct graphics effects and transformations into separate methods. This simplifies the process and reduces potential errors.
• Prioritizing Matrix Operations: Utilize Matrix.RotateAt and Matrix.Multiply instead of accumulating Matrix transformations, as it's more efficient and less prone to unforeseen outcomes.
• Optimized Canvas Selection: Employ a PictureBox, which is a non-System flat Label, as the canvas. It supports double-buffering and is designed for drawing.

Within the code, four zoom modes are implemented:

Zoom Modes

• ImageLocation: Image scaling is performed without altering its location on the canvas.
• CenterCanvas: The image remains centered on the canvas while being scaled.
• CenterMouse: The image scales and translates to align with the current mouse pointer location on the canvas.
• MouseOffset: The image is scaled and translated to maintain a relative position based on the initial mouse location on the image.

The included code sample generates rotation transformations and demonstrates the implementation of all four zoom modes. Zoom mode selection is handled by an enumerator named ZoomMode.

Visual Overview of Functionalities

Sample Code

The following code is provided:

• canvas: A custom PictureBoxEx control (that can be modified and extended) added to the Form.
• trkRotationAngle: TrackBar used for adjusting image rotation angle.
• radZoom_CheckedChanged: Event handler for zoom mode selection radio buttons.

In the canvas_Paint method, the drawing image is scaled and rotated using a series of Matrix transformations. The GetDrawingImageRect and GetDrawingImageCenterPoint methods are used to calculate the correct rectangle and center point for drawing the scaled image. By applying transformations in a specific order, the image can be zoomed and translated while maintaining its position on the canvas or relative to the mouse location.

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