According to one embodiment, a first correlation calculator calculates a correlation between first pixel blocks, and detects as first reference pixels actual pixels contained respectively in the first pixel blocks with the highest correlation. A second correlation calculator calculates a correlation between second pixel blocks, and detects as second reference pixels actual pixels contained respectively in the second pixel blocks with the highest correlation. The first pixel blocks include pixels arranged in a plurality of rows and columns The second pixel blocks include pixels arranged in at least one row less than the rows of the first pixel blocks and a plurality of columns. An interpolation calculator calculates, when the first reference pixels are located perpendicular to the actual pixel lines, the pixel value of the interpolation pixel based on the second reference pixels.