1. A computer-implemented method for correcting for dark current in a photosensor comprising a plurality of pixels, the method comprising: under control of one or more physical computing devices configured with specific computer-executable instructions, accessing, by the one or more physical computing devices, a scale factor and a bias factor for the plurality of pixels of the photosensor, wherein the plurality of pixels includes all the pixels of the photosensor, the scale factor and the bias factor depending at least partly on a temperature of the photosensor and a gain of the photosensor, and the scale factor and the gain factor both contributing to any dark current in the photosensor, the scale factor having the same value for each pixel in the plurality of pixels, and the bias factor having the same value for each pixel in the plurality of pixels; for each pixel in the plurality of pixels of the photosensor: accessing, by the one or more physical computing devices, a pixel value that represents a response of the pixel to receipt of light; accessing, by the one or more physical computing devices, an offset value for the pixel, the offset value not dependent on the temperature or the gain of the photosensor; determining, by the one or more physical computing devices, a corrected pixel value that depends at least partly on the pixel value, the scale factor, the bias factor, and the offset value, wherein the scale factor and the bias factor are global factors that are the same for each pixel in the plurality of pixels, and wherein the pixel value and the offset value are local factors capable of having values that are different for different pixels in the plurality of pixels; and providing, by the one or more physical computing devices, the corrected pixel value.