Image scanning apparatus

An image scanning apparatus, comprising:

• a processor;
• the processor capable of running software units;
• an image scanning unit configured to optically scan a document image of a document;
• a preprocessing unit, running on the processor, configured to generate an input image as a binary image from the document image;
• a projection image generating unit, running on the processor, configured to (a) try at each primary-scanning-directional target pixel position in the input image to detect a secondary-scanning-directional run that includes a predetermined number of continuous pixels or more along a secondary scanning direction, project the detected secondary-scanning-directional run at the primary-scanning-directional target pixel position and thereby generate a one-dimensional primary-scanning-directional-projection image, and (b) try at each secondary-scanning-directional target pixel position in the input image to detect a primary-scanning-directional run that includes a predetermined number of continuous pixels or more along the primary scanning direction, project the detected primary-scanning-directional run at the secondary-scanning-directional target pixel position and thereby generate a one-dimensional secondary-scanning-directional-projection image;
• a blank sheet determining unit, running on the processor, configured to determine that the document is a blank document at least on the basis of the number of runs in the primary-scanning-directional-projection image and the number of runs in the secondary-scanning-directional-projection image;
• wherein the blank sheet determining unit (a) determines that document is a blank document that includes a horizontal ruled line if the primary-scanning-directional-projection image does not include a predetermined number of runs nor more but the secondary-scanning-directional-projection image includes the predetermined number of runs or more, and (b) determines that document is a blank document that includes a vertical ruled line if the secondary-scanning-directional-projection image does not include the predetermined number of runs nor more but the primary-scanning-directional-projection image includes the predetermined number of runs or more;
• and
• the predetermined number is equal to or larger than 1, and specified on the basis of setting data.