1. An image processing apparatus comprising: an information embedding unit that embeds, into an image signal, decision information that is information about a specific parameter of an image; an image-signal transmission unit that sends to an external device the image signal with the decision information; an image-signal reception unit that receives from the external device the image signal with the decision information; an embedded-information extraction unit that extracts the decision information from the image signal received; a parameter setting unit that determines degree of alteration of the image based on the decision information extracted and sets an image processing parameter based on the degree of alteration determined; and an image processing unit that subjects the image signal received to image processing based on the image processing parameter set.