1. A method comprising: capturing, using a capturing device of a mobile device, a captured image containing: a dipstick having colored test reagents, and a color board comprising a grid of grey patches and a plurality of sets of reference color patches, said reference color patches reflecting variations in one of: illumination conditions, capturing capabilities of potential mobile devices, and response functions of capturing devices of the potential mobile devices, wherein each of the sets of reference color patches is tailored to span a color gamut of a respective one of said colored test reagents; deriving, based on the plurality of sets of reference color patches and the grid of grey patches on the captured image, local illumination parameters associated with the colored test reagents and the plurality of sets of reference color patches; normalizing local illumination of the captured image, based on the local illumination parameters; and interpreting the colored test reagents, based on the normalized local illumination and the reference color patches, in the captured image.