The disclosure provides a process whereby an image processing device may isolate an outline of an object from an image, and a method adapted for the image processing device. When the image processing device 1 defines a pixel point as a boundary point of an object, the image processing device 1 continues to search for an adjacent boundary point. When the image processing device 1 defines a pixel point as a non-boundary point of the image, the image processing device 1 continues to search for a boundary point from predetermined pixel points until all boundary points have been found unless it is determined that the image does not include an object.