Patent ID: 8224084

Claim:
An image processing method for converting a monochrome image into a color image, wherein, when the monochrome image is converted into the color image, a target color to be converted from each pixel of the monochrome image is decided based on first to fourth criteria according to a pixel value of said each pixel, the pixel value representing lightness of said each pixel of the monochrome image; wherein the method comprises: applying the first criterion to said each pixel to decide lightness of the target color for said each pixel; and applying one of the second to fourth criteria to said each pixel in accordance with the pixel value to decide a chromaticity of the target color, wherein, in the first criterion, black is assigned to the pixel value having a minimum value within a possible range that the pixel value can take, white is assigned to the pixel value having a maximum value within the range of the pixel value, or a color having lightness according to the lightness represented by the pixel value is assigned to the pixel value; wherein, in the second criterion, a color in a blue color region is assigned to the pixel value having a value near but excluding the minimum value, wherein, in the third criterion, a color in a yellow color region is assigned to the pixel value having a value near but excluding the maximum value; and wherein, in the fourth criterion, a color in a range of hue starting from the blue color region to the yellow color region by way of a red color region or a color in a range of hue starting from the blue color region to the yellow color region by way of a green color region is assigned to the pixel value having a value in a range between the value near the minimum value and the value near the maximum value but excluding the value near the minimum value and the value near the maximum value.