1. An image processing apparatus comprising: a color extraction unit that extracts pixels by using a plurality of thresholds for at least one color used in a plurality of sticky notes, from image information including information about the plurality of sticky notes, the plurality of thresholds being prepared in advance for a color space; a region cutting-out unit that cuts out at least one region which is a group of the pixels which are extracted by the color extraction unit, for each of the plurality of thresholds; a determination unit that determines a threshold to be employed, from the plurality of thresholds on the basis of the number of regions which are cut out by the region cutting-out unit; and a sticky-note-image cutting-out unit that cuts out at least one sticky note image from the image information by using the threshold determined by the determination unit.