Proposed in various embodiments of the present disclosure are a device and a method for image processing, whereby image conversion by dilation is carried out in a multimedia system. To this end, an electronic device for image processing may identify between a first unused area in a first picture and a second unused area in a second picture, the first unused area and the second unused area having the same time information. The electronic device may acquire fill values for replacing the first unused area and the second unused area, on the basis of a value acquired from the first unused area and a value acquired from the second unused area. The electronic device may acquire a first converted picture and a second converted picture by replacing the first unused area and the second unused area by using the acquired fill values.