1. An image processing apparatus comprising: event detecting means for detecting an event in accordance with a user's operation; boundary detecting means comprising separating means for separating a pixel value of a target image into a plurality of components and outputting component images, edge detecting means for detecting an edge of one component image outputted by said separating means and outputting an edge image, binarizing means for binarizing the edge image outputted by said edge detecting means and outputting the binarized image, and thin-line means for making the binarized image outputted by said binarizing means a thin-line image and outputting the thin-line image; extracting means for extracting a pixel corresponding to an object including a target pixel from the thin-line image, when the event detecting means detects the event at the position designated by the user's operation in a space direction of the target image, by setting, as the target pixel, a pixel of the thin-line image corresponding to the one component image at the position designated by the event, by storing a pixel value of the target pixel at the stored position corresponding to the position on the target pixel, by searching for a portion up to a thin-line area of the thin-line image in the space direction at the set target pixel as the origin, and by storing the pixel value searched at the stored position corresponding to the searched pixel position; a plurality of primary storing means for storing the pixel value corresponding to the object which is transferred by said extracting means; display means for displaying a plurality of screens corresponding to the plurality of primary storing means based on the pixel values of the pixels corresponding to the object stored in said extracting means; and object storing means for, when the event detecting means detects the event for selecting at least of a part of the object displayed on said display means by the user's operation, transferring the pixel value of the pixel stored in said primary storing means corresponding to the selected part and storing the pixel value at the stored position corresponding to the position of the pixel.