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libmodal_exposure a histogram to an image (with metadata) and returns what the new exposure/gain should be.

Configuration of libmodal_exposure is achieved through voxl-camera-server.conf

The parameters exposed include the following

ae_desired_msvthe desired mean sample value, a.k.a. the average value of pixels that the auto exposure algorithm should try to achieve in frame
ae_k_p_nsthe desired p_ns for the exposure algorithm
ae_k_i_nsthe desired k_i for the exposure algorithm
ae_max_ithe desired max_i for the exposure algorithm
ae_filter_alphaa low-pass filter constant that filters the calculated MSV to slow down responses - the filter used is an IIR filter
ae_ignore_fractionmaximum percentage of saturated (255) pixels that will be used in calculation of MSV. If there are more saturated_pixels / total_pixels, then additional saturated pixels are not used to calculate MSV. This helps prevent image getting too dark if there are large blobs of very bright light
ae_sloperatio that specifies how much gain vs exposure should be changed when trying to achieve desired MSV. Both gain and exposure linearly affect the pixel brightness, but gain and exposure have different effects on the image quality - mostly in the sense that gain affects granularity and that exposure affects motion blur.
ae_exposure_periodcontrols the duration where the cells of the camera sensor are exposed to light
ae_gain_periodthe gain period associated to the auto exposure (think of this as an amplification factor of the pixels)

Source code and README on Gitlab