To provide an image processing apparatus, image processing method, image processing program and recording medium, wherein a ratio to achromatize a source image is improved.

An image processing apparatus includes: a determination means for determining whether or not a source image is achromatized on the basis of features of the source image; and an achromatization means which performs achromatization for converting the source image into an achromatic image when the determination means determines that the source image is achromatized. The determination means includes: a constitutive color detecting means for detecting a plurality of constitutive colors constituting the source image; a by-colors achromatization means which separates the source image for each of the plurality of constitutive colors to generate a plurality of images by colors and achromatizes the plurality of images by colors to generate a plurality of images achromatized by colors; and a by-colors frequency detection means for detecting a frequency distribution of pixel values included in each of the plurality of images achromatized by colors. On the basis of detection results of the constitutive color detecting means and the by-colors frequency detection means, the determination means determines whether or not the source image is achromatized.