Most previous studies on non-line-of-sight optical camera communication (NLOS-OCC) were conducted as practical experiments; few relevant mathematical models have been proposed for simulation. This paper presents a simplified model for NLOS-OCC with a simple patterned reflective surface and proposes to directly decode the raw pixel values to improve the system performance. The model combines the mathematical models of a diffuse reflection channel and rolling shutter to obtain a normalized raw pixel value matrix of the pixel plane corresponding to the camera output image and realize visualization. Based on this model, we analyze the threshold selection and anti-interference ability of the conventional decoding scheme, and propose the sorting pre-decoding scheme: first sorting the pixel values by rows before decoding can effectively reduce the impact of the reflective surface pattern and enhance the system's anti-interference ability.