Patent ID: 8331696

Claim:
An update region detection device that calculates a difference absolute value for each pixel between a current frame and a previous frame, the previous frame being a frame preceding the current frame, and detects, as an update region whose plot data change from the previous frame to the current frame, a region including a shape defined by pixels where the difference absolute value is equal to or greater than a first threshold and including a pixel where the difference absolute value is equal to or greater than a second threshold, the second threshold being a value greater than the first threshold, the update region detection device comprising: a pixel comparison unit that compares a difference absolute value between values of pixels at the same position in each of the current frame and the previous frame, with the first threshold and the second threshold; and an update region extraction unit that extracts, as an update includes a shape defined by pixels equal to or greater than the first threshold and which includes pixels equal to or greater than the second threshold, wherein the pixel comparison unit sequentially compares pixels of the previous frame and the current frame for each row, records, for each column, a row coordinate of an upper end and a row coordinate of a lower end, at each of which the difference greater than the first threshold has been detected and records whether there is a pixel where the difference greater than the second threshold has been detected is present between the upper end and the lower end, and the update region extraction unit performs a process for referring to a record obtained by the pixel comparison unit; at a point when a predetermined number of continuous rows where the difference greater than the first threshold has not been detected are present, extracting update columns which are a group of columns where the difference greater than the first threshold has been detected and which include a pixel where the difference greater than the second threshold has been detected, and determining, for each of the extracted update columns, a rectangle defined by a row coordinate of an uppermost end and a row coordinate of a lowermost end, at each of which the difference greater than the first threshold has been detected, and by a columns coordinate of a left end and a column coordinate of a right end in the update columns, as the update region.