IMAGE SYNTHESIZER

PROBLEM TO BE SOLVED: To provide an image synthesizer capable of continuously outputting an overlay image even when a base image signal containing a chroma key color area on which an overlay image is overlaid becomes non-signal.SOLUTION: An image synthesizer includes: a first overlay image processing circuit 2 for storing a first overlay image displaying area position and size, and changing the first overlay image position and size accordingly; a second overlay image processing circuit 3 for carrying out the same processes for a second overlay image; a base image nonexistence detection circuit for determining the existence or nonexistence of a base image; and a chroma key determination circuit 4 for determining the chroma key color portion of the base image. When the base image nonexistence detection circuit determines that the base image is not existing, the image synthesizer outputs the first and the second overlay images processed by the first overlay image processing circuit 2 and the second overlay image processing circuit 3.