We present a generalized white-patch technique able to rapidly detect color cast of natural images. Instead of relying on the chromatic information of a single perfectly reflective patch in the image, as pure white-patch models do, we consider a connected region of pixels that will serve as white reference for the method. The pixels belonging to the white reference region must comply with three properties: 1) they do not have to be completely saturated; 2) they must belong to the p % of pixels with brightest intensity in the whole image (where p is a parameter of the model); 3) the area of the connected region formed by these pixels must overcome a threshold of significance A (a second parameter). Color cast is detected if the average intensity in the three separated chromatic channels RGB is distant enough from a neutral grey level, where the distance is measured through an angular metric.
Jose Luis Lisani, Ana Belén Petro, Edoardo Provenzi, Catalina Sbert, "A generalized white-patch model for fast color cast detection in natural images" in Proc. IS&T Int’l. Symp. on Electronic Imaging: Retinex at 50, 2016, https://doi.org/10.2352/ISSN.2470-1173.2016.6.RETINEX-318