1. A projector for projecting an image, comprising: a memory device containing a plurality of memory blocks for storing a plurality of image data corresponding to different image sources respectively; an integrating module coupled to the memory device for selectively reading the plurality of image data from the memory device, and for integrating at least two image data read from the memory device into an image data stored in the memory device corresponding to the image; a projecting module for projecting the image; and a transceiving module for receiving a first image data and for determining a first image source corresponding to the first image data; wherein the integrating module selects a first memory block corresponding to the first image source from the memory blocks to store the first image data in the first memory block, wherein the integrating module comprises an analyzing unit for detecting if the first memory block exists in the memory device, wherein if the detection result of the analyzing unit indicates that the first image source does not correspond to any memory block in the memory device, the analyzing unit transmits a response message to the first image source via the transceiving module to try to establish a connection between the projector and the first image source.