A method for demosaicking a digital image is provided. Pixels of the digital image are processed in an order from the upper-left to lower-right of the digital image. If a current-processed pixel is a second color or a third color, a first sub-window centered at the current-processed pixel is generated. A first mask is used to select a first plurality of prior-processed pixels. A set of direction weightings of the current-processed pixel is calculated according to stored direction weightings of the first plurality of prior-processed pixels. An interpolating direction of the current-processed pixel is determined according to the set of direction weightings of the current-processed pixel. A value of a first color for the current-processed pixel is calculated based on the set of direction weightings of the current-processed pixel and values of the first color of pixels of the first color in the first sub-window.