Image processing apparatus capable of suppressing errors related to document conveying speed and data transfer rate, method of controlling image processing apparatus, and storage medium

A method of controlling an image processing apparatus including a reading unit that reads a document sheet, and an image processing unit that performs an image processing process on image data obtained by reading the document sheet, comprising:

• controlling a conveying speed of the document sheet based on a thickness of the document sheet;
• controlling a frequency of an image transfer clock for transferring image data of the document sheet from the reading unit to the image processing unit;
• determining a first frequency based on whether or not the image processing process is executed in parallel with any other image processing process different from the image processing process;
• determining a second frequency based on the thickness of the document sheet;
• and
• using a frequency which is the lower of the first frequency and the second frequency as the frequency of the image transfer clock.

A non-transitory computer-readable storage medium storing a computer-executable program for executing a method of controlling an image processing apparatus including a reading unit that reads a document sheet, and an image processing unit that performs an image processing process on image data obtained by reading the document sheet,

• wherein the method comprises:
• controlling a conveying speed of the document sheet based on a thickness of the document sheet;
• controlling a frequency of an image transfer clock for transferring image data of the document sheet from the reading unit to the image processing unit;
• determining a first frequency based on whether or not the image processing process is executed in parallel with any other image processing process different from the image processing process;
• determining a second frequency based on the thickness of the document sheet;
• and
• using a frequency which is the lower of the first frequency and the second frequency as the frequency of the image transfer clock.