Image processing apparatus and method of generating face image

An image processing apparatus comprising:

• a storing unit which stores in advance, as partial instance images, a plurality of partial face images obtained by photographing a face image of each of a plurality of persons on a plurality of photographing conditions, and extracting a plurality of specific parts from each photographed face image while associating each of the specific parts with a corresponding person and a corresponding photographing condition;
• at least one memory storing computer-executable instructions;
• and
• at least one processor configured to execute the computer-executable instructions to implement:
• an obtaining unit configured to obtain a photographing condition of an input face image;
• an approximating unit configured to approximate, for each of the specific parts, a specific part of the input face image by a first linear combination of the partial instance images of the specific part stored in the storing unit in association with respective persons and the photographing condition corresponding to the photographing condition of the input face image;
• a deciding unit configured to decide, for each specific part of the input face image, a second linear combination of the partial instance images of the specific part stored in the storing unit in association with respective persons and each of a plurality of predetermined photographing conditions so that a weight for a partial instance image associated with each person in the second linear combination corresponds to the weight for the partial instance image associated with that person in the first linear combination of that part;
• and
• a generating unit configured to generate an approximate image of the input face image with respect to each of the predetermined photographing conditions, by synthesizing the second linear combinations obtained for the plurality of specific parts of the input face image for each predetermined photographing condition.

A non-transitory computer-readable storage medium storing a program which causes a computer to execute steps of:

• storing in advance, as partial instance images in a storing unit, a plurality of partial face images obtained by photographing a face image of each of a plurality of persons on a plurality of photographing conditions and extracting a plurality of specific parts from each photographed face image, while associating each of the specific parts with a corresponding person and a corresponding photographing condition;
• obtaining a photographing condition of an input face image;
• approximating, for each of the specific parts, a specific part of the input face image by a first linear combination of the partial instance images of the specific part stored in the storing unit in association with respective persons and the photographing condition corresponding to the photographing condition of the input face image;
• deciding, for each specific part of the input face image, a second linear combination of the partial instance images of the specific part stored in the storing unit in association with respective persons and each of a plurality of predetermined photographing conditions so that a weight for a partial instance image associated with each person in the second linear combination corresponds to the weight for the partial instance image associated with that person in the first linear combination of that part;
• and
• generating an approximate image of the input face image with respect to each of the plurality of predetermined photographing conditions, by synthesizing the second linear combinations obtained for a plurality of specific parts of the input face image.