To restrict the waste of ink by automatically reducing an image to a size by which the image can be printed with a quantity of remaining ink when the quantity is not sufficient to print printing data and transferring the data to an ink discharge type printing apparatus.

A driver 101 of a host computer 100 converts from a printing image data 90 to a printing data that can be handled by a printer 130, calculates a quantity of ink necessary for the printing, compares the quantity with a remaining quantity information received from the printer 130, judges whether or not the printing is possible, and forms printing data of a reduced size from the printing image data 90. A detecting part 104 for detecting a quantity of remaining ink returns each quantity of ink of an ink tank 105 to a CPU 106. The CPU 106 calculates the quantity of remaining ink based on each ink quantity value detected by the detecting part 104 according to a program stored in a ROM 109, and transfers it to the host computer 100 in response to a request from the driver 101.