1. A computer-implemented method to estimate noise in an image, the method comprising: determining a plurality of patches of pixels in the image; determining, for each patch of pixels, feature pixels in the patch that are included in a particular image feature at least partially depicted in the patch; determining, for each patch of pixels, an error estimate, wherein the error estimate is based on an amount by which pixel values of the feature pixels in the patch of pixels are different from an estimated polynomial relationship between the feature pixels in the patch of pixels; and selecting one of the error estimates as a noise level estimate for the image.