I recommend you amend the erase tool when editing a bitmapped image such that when one holds down the shift key, the eraser locks to either the horizontal or vertical axis.  Further, if one hovered over a particular place on the image and left-clicked once, then moved the cursor to another position, held down the shift key and left-clicked once, what would be erased would be a straight line between both positions.  This improvement would significantly reduce the time it takes to erase unwanted portions of the image.  This is a feature common to other apps such as Adobe's Illustrator.  Thank you for considering this improvement.