Gradation conversion processing

A computer-readable storage medium storing a program for making a computer execute a method of gradation conversion of an image, the method comprising:

• a first determination step of determining a first gradation conversion function for converting a pixel value width of an image based on a pixel value width of a predetermined region in the image;
• a second determination step of determining a second gradation conversion function for converting an image based on a pixel value in a target region in an image;
• and
• a gradation converting step of applying the first and second gradation conversion functions to an image such that, in a gradation-converted image on an image display medium, a pixel value in the predetermined region falls within a target range and a pixel value in the target region is a target level.

An apparatus which performs gradation conversion of an image, comprising:

• a first determination unit adapted for determining a first gradation conversion function for converting a pixel value width of an image based on a pixel value width of a predetermined region in the image;
• a second determination unit adapted for determining a second gradation conversion function for converting an image based on a pixel value in a target region in an image;
• and
• a gradation conversion unit adapted for applying the first and second gradation conversion functions to an image such that, in a gradation-converted image on an image display medium, a pixel value in the predetermined region falls within a target range and a pixel value in the target region is a target level.

A system which includes a plurality of apparatuses and performs gradation conversion of an image, comprising:

• a first determination unit adapted for determining a first gradation conversion function for converting a pixel value width of an image based on a pixel value width of a predetermined region in the image;
• a second determination unit adapted for determining a second gradation conversion function for converting an image based on a pixel value in a target region in an image;
• and
• a gradation conversion unit adapted for applying the first and second gradation conversion functions to an image such that, in a gradation-converted image on an image display medium, a pixel value in the predetermined region falls within a target range and a pixel value in the target region is a target level.