Canon PIXMA MG4200 Series On-Screen Manual page 796

Click Cancel to cancel the scan.
10.
Adjust the scanned images as required.
Use the Toolbar to rotate or zoom in/out, or drag the images to adjust their positions.
Note
Select the Adjust cropping frames checkbox to specify the area to be saved.
Adjusting Cropping Frames
To scan an item again, select the image in the Preview area or the thumbnail at the top of the
screen, then click
again.
11.
Click Save.
(Delete). The selected image is deleted, allowing you to scan the item