Disclosed is an image processing apparatus composed in a hierarchical architecture of a hardware resource, a first control program over the hardware resource, a second control program and an application program over the first control program. The first control program includes a first API for receiving a first request relating to image processing from the second control program and a second request relating to image processing from the application program, and controls, on receiving either of the first and second requests, the hardware resource to perform image processing based on the received request. The second control program includes a second API publicly released in advance for receiving a third request relating to image processing from an external source, converts the received third request to a command supported by the first API, and passes the command as the first request to the first control program.