An image processing apparatus comprises a print request data stream reception unit for externally receiving a print request data stream, a print job controller for controlling a print job of interpreting the print request data stream and executing image formation, and a filter for executing a data process to the print request data stream and thus generating the processed print request data stream. The image processing apparatus sends the print request data stream received by the print request data stream reception unit to the filter through a first interface, and sends the processed print request data stream generated by the filter to the print job controller through a second interface.