1. An image transmission apparatus comprising: an imaging portion to output a pick up image obtained by picking up a shooting object; a display portion to display said pick up image; a masked region determining portion to determine a masked region to mask at least a part of said pick up image displayed on said display portion; a feature extraction portion to extract a feature from said pick up image; a masked region movement portion to move said masked region determined by said masked region determining portion according to a change in a position of said feature; a composite image generation portion to generate a composite image in which said masked region of said pick up image is converted to another image; and a transmission portion to transmit said composite image.