Image forming apparatus and method for determining

A method for determining whether an image recorded by a printing apparatus contains a defect, the printing apparatus comprising:

• a plurality of heads configured to record an image;
• a plurality of head controlling circuits connected to the plurality of heads in one-to-one correspondence, the plurality of head controlling circuits being connected with one another serially, each of the plurality of head controlling circuits being configured to control a corresponding one of the plurality of heads to record a part of the image based on master data;
• and
• a master transmitter configured to transmit the master data to a most upstream one of the plurality of head controlling circuits,
• the method comprising:
• passing the master data received by the most upstream one of the plurality of head controlling circuits serially downstream onto a most downstream one of the plurality of head controlling circuits,
• causing each of the plurality of head controlling circuits to generate differential data indicating a difference between the master data and read data, the read data being generated by reading the recorded image, and
• determining whether the recorded image contains the defect based on the differential data.