1. An image signal processor, comprising: an image sensor interface configured to receive pixel data from an image sensor; a front-end pixel data processing circuit configured to: receive pixel data for an image frame in an image sensor pixel data format; and convert the pixel data in the image sensor pixel data format to a different color space format; a back-end pixel data processing circuit configured to perform one or more noise filtering or color processing operations on the pixel data from the front-end pixel data processing circuit; an output circuit configured to receive pixel data from the back-end pixel data processing circuit and output the pixel data for the image frame to a system memory; and a keypoint detection circuit configured to: receive pixel data from the image sensor interface in the image sensor pixel data format or receive pixel data after processing by the front-end pixel data processing circuit or the back-end pixel data processing circuit; perform a keypoint detection operation on the received pixel data to detect one or more keypoints in the image frame; and output to the system memory a description of the one or more keypoints.