About resizing or cropping an object
Resizing When you select an object, sizing handles appear at the corners and along the edges of the selection rectangle. You can resize an object by dragging its sizing handles, or you can resize it more precisely by specifying percentages for the object's height and width.
Resize an object by a specific percentage
Maintain the proportions of an object while resizing it
Cropping If the object is a picture
Restoring You can restore pictures that have been cropped or resized. No matter how many times the picture has been changed, Microsoft Graph keeps track of its original size when it was first inserted in your chart. How to restore a picture to its original size.