Adjustment in the amount of projected image distortion correction

A projector that projects an image on a projection surface, comprising:

• an image distortion correction part that produces a distortion correction image by transforming an original image based on a set amount of distortion correction so as to correct distortion of the projected image that occurs if the image is projected obliquely on the projection surface;
• a desired position specification part that specifies desired positions at which four vertexes forming an outline form of the projected image are to be located so as to adjust the outline form of the projected image to a desired outline form;
• a distortion correction amount adjuster that adjust an amount of distortion correction, set in the image distortion correction part, based on the desired positions specified by the desired position specification part;
• and
• an outline production part that produces an outline corresponding to the desired outline form of the projected image to be formed by specifying the desired positions;
• in adjusting the amount of distortion correction set in the image distortion correction part, the distortion correction amount adjuster:
• if the desired position specification part specifies the desired positions, calculates values of the amount of distortion correction for the desired outline form to be formed based on the desired positions;
• judges whether all the calculated values of the amount of distortion correction are within a predetermined range where the original image is transformable into the distortion correction image;
• if all the calculated values of the amount of distortion correction are within the predetermined range, sets the calculated values of the amount of distortion correction in the image distortion correction part;
• and
• if a value out of the calculated values of the amount of distortion correction is beyond the predetermined range, makes the outline production part produce outlines corresponding to at least part of the desired outline form and makes an outline form corresponding to the amount of distortion correction beyond the predetermined range different from an outline form corresponding to the amount of distortion correction within the predetermined range so that each is identified, instead of setting the calculated values of the amount of distortion correction in the image distortion correction part.