A method is disclosed for determining wettability in a subsurface reservoir. Embodiments of the method utilize image analysis techniques for determining wettability indicator values. Wettability indicator values may be determined based on a hydrocarbon wet fraction and a water wet fraction of pore linings, which may both be determined by image analysis of pore walls lined with hydrocarbons using images of sections obtained from core samples. Further details and advantages of various embodiments of the method are described in more detail herein.