Image processing device, image processing method, and storage medium

An image processing method comprising:

• receiving, by a processor, a visible image of a face;
• receiving, by the processor, a near-infrared image of the face;
• adjusting, by the processor, brightness of the visible image based on a frequency distribution of pixel values of the visible image and a frequency distribution of pixel values of the near-infrared image, by adjusting the pixel values of the visible image in such a way that at least a part of a shape of the frequency distribution of the visible image approaches a shape of the frequency distribution of the near-infrared image in a range of the pixel values excluding a first range including a darkest pixel value and a second range including a brightest pixel value of the near-infrared image;
• specifying, by the processor, a relative position at which the visible image is related to the near-infrared image;
• inverting, by the processor, adjusted brightness of the visible image;
• detecting, by the processor, a region of a pupil from a synthetic image obtained by adding up the visible image of which the brightness has been inverted and adjusted and the near-infrared image based on the relative position;
• detecting, by the processor, an iris region based on the detected the region of the pupil;
• changing, by the processor, a pixel value of the region of the pupil included in the iris region;
• performing, by the processor, iris authentication using the iris region including the region of pupil having the pixel value that has been changed;
• and
• outputting, by the processor, a result of the iris authentication.

A non-transitory computer-readable storage medium storing a program that when executed by a computer causes the computer to execute processing of:

• receiving a visible image of a face;
• receiving a near-infrared image of the face;
• adjusting brightness of the visible image based on a frequency distribution of pixel values of the visible image and a frequency distribution of pixel values of the near-infrared image, by adjusting the pixel values of the visible image in such a way that at least a part of a shape of the frequency distribution of the visible image approaches a shape of the frequency distribution of the near-infrared image in a range of the pixel values excluding a first range including a darkest pixel value and a second range including a brightest pixel value of the near-infrared image;
• specifying a relative position at which the visible image is related to the near-infrared image;
• inverting adjusted brightness of the visible image;
• detecting a region of a pupil from a synthetic image obtained by adding up the visible image of which the brightness has been inverted and adjusted and the near-infrared image based on the relative position;
• detecting an iris region based on the detected the region of the pupil;
• changing a pixel value of the region of the pupil included in the iris region;
• performing iris authentication using the iris region including the region of pupil having the pixel value that has been changed;
• and
• outputting a result of the iris authentication.