Storage medium, method, and device for evaluating importance of in-image region

Provided is a device for evaluating the importance of an in-image region and that can appropriately evaluate the importance in terms of meaning of an in-image region. A processing unit performs a process including color reduction with respect to an evaluation subject region of an image. An importance determination unit determines the importance of the evaluation subject region on the basis of the degree of magnitude of the error between the pre-processing signal value of the evaluation subject region and the post-processing signal value of the evaluation subject region.