PROBLEM TO BE SOLVED: To provide an image display device, an image region detection method and a computer program capable of accurately detecting an image region under specific conditions within a display image.SOLUTION: A determination is made as to whether each pixel of an input image is a monochrome pixel, a monochrome line region consisted of monochrome pixels is detected out of each line of the input image, and a monochrome image region consisted of a plurality of monochrome line regions is detected. When a starting point or an ending point of detected two monochrome image regions coincides, and the number of lines between the two monochrome image regions is equal to or below a sixth threshold, the monochrome image region detection on one or a plurality of lines between the two monochrome image regions is performed again. To a monochrome image region whose size in the line direction is smaller in the two monochrome image regions, a part of the lines between the two effective image regions is added to make a new monochrome image region.
