According to the embodiments, there is provided an image processing apparatus including: an acquisition section configured to acquire 3×3 pixel block data to have one red pixel at a center; an estimation section configured to compute blue value differences between blue values of diagonal pairs of blue pixels in the block data, and to estimate a direction of a contrast boundary based on the blue value differences; and a processing section configured to compute a computed blue value based on the blue values of the four blue pixels within the block data according to the estimated direction of the contrast boundary, to compute a computed green value based on green values of two green pixels within the block data, and to output a color image pixel to have a red value of the red pixel and the computed blue and green values.