1. An image transmission system having a transmission device and a reception device, wherein the transmission device comprising: a division unit configured to divide image data into a plurality of regions on the basis of a similarity of pixels; and a transmission unit configured to transmit the image data and region representative points of the plurality of regions, and the reception device comprising: a reception unit configured to receive the image data and the region representative points transmitted from said transmission device; and a label generation unit configured to generate region labels used for identifying the plurality of regions, using the image data and the region representative points.