Methods and systems for camera characterization in terms of response function, color, and vignetting under non-uniform illumination

A method for estimating a color model of an imaging device, comprised of the response function and the color mapping, under generic illumination, the method comprising:

• i. acquiring at least one calibration image of a scene with at least two regions of constant albedo from an arbitrary pose;
• ii. segmenting the calibration image into regions of constant albedo and grouping the pixels in each region into a set , the set of points with albedo ρn;
• iii. deriving equations for the estimation using
• f−1(d(x))=u(x)ρ′(x)
• where x are the pixel coordinates that correspond to a scene point, d(x) is the acquired image and is defined as a vector of Nc elements dc(x) that correspond to values on pixel x and channel c, f−1(d) is the inverse camera response function, a function vector of elements f c−1(dc), u(x) is the albedo-normalized irradiance, a scalar function, and ρ′ is the albedo vector of size Nc in the color space of the camera and is defined by elements ρ′c for each channel c such that
• ρ=Mρ′
• with ρ being the albedo vector of size Ns in the output color space and is defined by elements ρs for each channel s, and M being a color mapping matrix of size Ns by Nc and composed of rows msT;
• and
• iv. determining the color model of the imaging device by solving the equations derived in step iii using a suitable solver or optimization scheme.