1. An image signal processor comprising: a central processing unit (CPU) configured to receive image data and positional information of phase detection pixels from an imaging device, extract first phase detection pixel data and second phase detection pixel data from the image data using the positional information of the phase detection pixels, compute first phase graphs from the first phase detection pixel data based upon moving a first window, compute second phase graphs from the second phase detection pixel data based upon moving a second window, compute disparities of the phase detection pixels using the first phase graphs and the second phase graphs, and generate a depth map based upon the disparities.