A method for combining a background image in an image file generating device with a real-time external picture that a camera part inputs, comprising: reading an original background image from a memory, wherein the original background image consists of a background region for the appearance of the background image and a preview region for the appearance of the real-time external picture; generating an update background image by assigning pixels of the original background image to either a selected preview region or a selected background region, characterized in that: the pixel data value of each pixel of the original background image is modified by setting the least significant bit of the respective pixel data value as a region classification value such that pixels belonging to the selected preview region and pixels belonging to the selected background region have pixel data values with different least significant bit settings; displaying the background region using the update background image and displaying the preview region using the real-time external picture, wherein the background region and the preview region are identified by the region classification value; and generating and storing a digital image corresponding to the displayed update background image and the displayed real-time external picture when a capture instruction is inputted. reading an original background image from a memory, wherein the original background image consists of a background region for the appearance of the background image and a preview region for the appearance of the real-time external picture; generating an update background image by assigning pixels of the original background image to either a selected preview region or a selected background region, characterized in that: the pixel data value of each pixel of the original background image is modified by setting the least significant bit of the respective pixel data value as a region classification value such that pixels belonging to the selected preview region and pixels belonging to the selected background region have pixel data values with different least significant bit settings; displaying the background region using the update background image and displaying the preview region using the real-time external picture, wherein the background region and the preview region are identified by the region classification value; and generating and storing a digital image corresponding to the displayed update background image and the displayed real-time external picture when a capture instruction is inputted. the pixel data value of each pixel of the original background image is modified by setting the least significant bit of the respective pixel data value as a region classification value such that pixels belonging to the selected preview region and pixels belonging to the selected background region have pixel data values with different least significant bit settings; displaying the background region using the update background image and displaying the preview region using the real-time external picture, wherein the background region and the preview region are identified by the region classification value; and generating and storing a digital image corresponding to the displayed update background image and the displayed real-time external picture when a capture instruction is inputted.