ABSTRACT
Automatic image colorization is the task of adding colors to a grayscale image without any user intervention. This problem is ill-posed in the sense that there is not a unique colorization of a grayscale image without any prior knowledge. Indeed, many objects can have different colors. This is not only true for artificial objects, such as plastic objects
which can have random colors, but also for natural objects such as tree leaves which can have various nuances of green and brown in different seasons, without significant change of shape.
