1. A method comprising: receiving, from an image-capture device coupled to an autonomous vehicle, an image of a field of view of the autonomous vehicle, wherein the image comprises a plurality of image portions; calculating, for each given image portion, a respective score indicating a level of confidence that the given image portion represents an illuminated component of a traffic light, wherein calculating the respective score for the given image portion comprises identifying at least one area within the given image portion and determining color values and luminance values of pixels in the at least one area; identifying, from among the plurality of image portions, one or more candidate portions as image portions having a score exceeding a threshold level of confidence; determining that a particular candidate portion represents an illuminated component of a traffic light; and based on the particular candidate portion representing an illuminated component of a traffic light, providing instructions executable by a computing device to control the autonomous vehicle.