Abstract: An image composing method and apparatus is provided which can compose a mixed image with no increased hardware scale and no reduced processing speed. A subtracting means (13) is used to calculate a difference in pixel value between a first image and a second image, each having three color information components and one additional information component. Each of the first and second image pixel values may have all the pixel values of zero. The result of subtraction is multiplied by a mixing factor in a multiplying means (15). For the mixing factor, any one of the additional information components or fixed values of the first and second image pixel values are selected. The components are of a same value. In a adding means 17, any of two image pixel values is added to the result of multiplication to produce a mixed image.