By applying approximate computing performance metrics are improved. Memristors can be used to perform logical calculations along with data storage. Approximate computing in memory, particularly using memristive stateful logic, has not been explored yet. In this paper, we combine these two concepts (approximate computing and in-memory computation) and propose a novel algorithm for IMPLY-based adders to implement an approximate full-adder. The proposed approximate full-adder was assessed in an image processing application, and different error quality metrics were assessed. Our study shows that the proposed method can achieve up to 40% improvement, whereas maintaining the introduced error in an acceptable range.