1. An image registration method, comprising: receiving a first image from an image sensor, the first image having a first number of rows, each row having a second number of pixels; receiving a second image from the image sensor, the second image having the first number of rows, each row having the second number of pixels, wherein each row in the second image has a corresponding row in the first image and each pixel in the second image has a corresponding pixel in the first image; identifying a subset of rows in the second image; and registering the first image and the second image using only the subset of rows in the second image and the corresponding subset of rows in the first image.