The invention relates to an image forming method and an image forming apparatus (4). The image forming apparatus (4) includes an input luminance range recognition unit (462), an output luminance range recognition unit (463), and a luminance range expansion unit (464). The input luminance range recognition unit (462) is configured to acquire input luminance information from multi-gradation monochrome image data, to generate a luminance histogram, and to recognize, based on a minimum luminance value and a maximum luminance value of the luminance histogram, an input luminance range. The output luminance range recognition unit (463) is configured to recognize an output luminance range. The luminance range expansion unit (464) is configured to perform a mapping process for mapping input luminance information of pixels within the image range into the output luminance range, and to expand the input luminance range to a maximum luminance range. Gradation reproducibility is maintained within a portion of the image or image area.
