Techniques for creating characterization matrices for reflectance, illuminance, or sensor response

A computer-implemented method for extrapolating an illuminance profile, the method comprising:

• acquiring, by a processor, an image of a scene that is illuminated by light produced by an illuminant,
• wherein the image is captured by a multi-channel image sensor that includes multiple sensor channels corresponding to multiple response profiles, and
• wherein the image includes multiple objects having known reflectances corresponding to multiple reflectance profiles;
• establishing, by the processor, a fingerprint by element-wise multiplying each response profile of the multiple response profiles and each reflectance profile of the multiple reflectance profiles;
• calculating, by the processor, illuminance for each wavelength in a predetermined spectrum by taking the dot product of the fingerprint and a wavelength-specific vector of coefficients;
• and
• generating, by the processor, an illuminance profile based on the illuminance.

A computer-implemented method for extrapolating a sensor response profile, the method comprising:

• acquiring, by a processor, a first series of images captured by a multi-channel image sensor in conjunction with a series of flashes produced by a multi-channel light source,
• wherein the multi-channel image sensor includes multiple sensor channels,
• wherein the multi-channel light source includes multiple color channels, and
• wherein each image in the first series of images is captured by the multiple sensor channels in conjunction with a flash produced by a color channel of the multiple color channels;
• acquiring, by the processor, a reference image captured by the multi-channel image sensor in conjunction with no flash;
• creating, by the processor, a second series of images by subtracting, on a per-pixel basis, first pixel values associated with the reference image from second pixel values associated with the first series of images;
• for each sensor channel of the multiple sensor channels,
• identifying, by the processor, a corresponding batch of pixel values in the second series of images;
• and
• generating, by the processor, a response profile for each sensor channel of the multiple sensor channels based on the corresponding batch of pixel values.