This paper presents a performance evaluation of large-scale parallel image compositing on a T2K Open Supercomputer. Traditional image compositing algorithms were not primarily designed for exploiting the combined message passing and the shared address space parallelism provided by systems such as T2K Open Supercomputer. In this study, we investigate the <i>Binary-Swap</i> image compositing method because of its promising potential for scalability. We propose some improvements to the <i>Binary-Swap</i> method aiming to fully exploit the hybrid programming model. We obtained encouraging results from the performance evaluation conducted on <i>Todai Combined Cluster</i>, a T2K Open Supercomputer at the University of Tokyo. The proposed improvements have also shown a high potential to tackle the large-scale image compositing problem on leading-edge HPC systems where an ever increasing number of processing cores is involved.