Image Forming Apparatus That Prints Out Multi-Gradation Monochrome Image Maintaining Gradation Reproducibility, and Image Forming Method

An image forming method comprising:

• acquiring input luminance information from multi-gradation monochrome image data in which a portion of an image range is selected;
• generating a luminance histogram;
• determining, based on a minimum luminance value and a maximum luminance value of the luminance histogram, an input luminance range in which input luminance information of the image range is distributed;
• determining an output luminance range supported by the image forming unit;
• performing a mapping process for mapping input luminance information of pixels within the image range into the output luminance range;
• and
• expanding the input luminance range to a maximum luminance range to be dealt with by the image forming unit.

A terminal apparatus serving as an information processing apparatus, the terminal apparatus comprising:

• an operation unit configured to receive data from an image generation apparatus and to receive an input operation indicating a selection of an image range in the multi-gradation monochrome image;
• an external interface connected to a display apparatus;
• a control unit, wherein the control unit operates as an input luminance range recognition unit, an output luminance range recognition unit, a luminance range expansion unit, and a negative-positive inversion unit, wherein
• the input luminance range recognition unit is configured to i) acquire input luminance information from the multi-gradation monochrome image data in which a portion of an image range is selected, ii) generate a luminance histogram, and iii) determine, based on a minimum luminance value and a maximum luminance value of the luminance histogram, an input luminance range in which input luminance information of the image range is distributed;
• an output luminance range recognition unit configured to determine an output luminance range supported by the display apparatus;
• and
• a luminance range expansion unit configured to i) perform a mapping process for mapping input luminance information of pixels within the image range into the output luminance range, and ii) expand the input luminance range to a maximum luminance range supported by the display apparatus;
• and
• a display execution instruction unit that realizes a display execution instruction function, and performs a process for displaying a multi-gradation monochrome image on the display apparatus.