An image processing method for converting a first image, which is expressed in a colorimetric system made up of a plurality of color components and is constituted of a plurality of pixels each holding color information corresponding to a single color component, to a second image constituted with a plurality of pixels all holding color information corresponding to at least one common color component, comprising: a color difference information generation step in which color difference information is generated by using color information in the first image; a color gradient analysis step in which a color gradient indicating an extent of color change is determined based upon the color difference information having been generated; and an image conversion step in which the first image is converted to the second image based upon the color gradient having been determined, wherein: in the color gradient analysis step, a color index to be used to evaluate color in correspondence to each pixel is generated based upon the color difference information and the color gradient is determined based upon the color index having been generated; characterized in that the image conversion step includes a color difference information correction step based upon the color difference information and color gradient in which a decision is made as to whether or not to execute the correction processing based upon the color gradient on the color difference information having been generated by using the color information in the first image. a color difference information generation step in which color difference information is generated by using color information in the first image; a color gradient analysis step in which a color gradient indicating an extent of color change is determined based upon the color difference information having been generated; and an image conversion step in which the first image is converted to the second image based upon the color gradient having been determined, wherein: in the color gradient analysis step, a color index to be used to evaluate color in correspondence to each pixel is generated based upon the color difference information and the color gradient is determined based upon the color index having been generated; characterized in that the image conversion step includes a color difference information correction step based upon the color difference information and color gradient in which a decision is made as to whether or not to execute the correction processing based upon the color gradient on the color difference information having been generated by using the color information in the first image. in the color gradient analysis step, a color index to be used to evaluate color in correspondence to each pixel is generated based upon the color difference information and the color gradient is determined based upon the color index having been generated; characterized in that the image conversion step includes a color difference information correction step based upon the color difference information and color gradient in which a decision is made as to whether or not to execute the correction processing based upon the color gradient on the color difference information having been generated by using the color information in the first image.