It is determined whether a repeating pattern is present in an image (100). When no repeating pattern is present, the image is divided into patch images, the resultant patch images are used to create a random repeating pattern, and the random repeating pattern is output (108). In addition, when the number of repetitions of the repeating pattern in the image is 2×2 or more (102), the repetition period is determined by transforming pixel values into frequency coefficients, and the repeating pattern is extracted based on the result of determining the repetition period, and is output (104). When the number of repetitions of the repeating pattern in the image is less than 2×2, the repetition period is determined by performing division using local maximum values of autocorrelation coefficients, and the repetition pattern is extracted based on the result of determining the repetition period (106).