1. An image processing apparatus, comprising: a controller configured to set a detection parameter; a face detection circuit including a dedicated hardware configured to detect first face information in an input image based on the detection parameter, wherein the first face information indicates a face detection range; and a programmable signal processing circuit configured to detect second face information based on the first face information, wherein the controller is configured to update the detection parameter based on the second face information in accordance with a rewritable program including a face detection program for detecting the second face information in the input image.