To crop an image after adding into design area, just click on image and select crop tool

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The new popup show up

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The image will be cropped with the exact position you put into the viewer.

There are some tweaks to make your image align better such as:

Center: move selection to center of image
Horizontal center: move selection align to horizontal center
Vertical Center: move selection top align to middle
Square: make selection square
After selected area, just press Save button