A cost-effective demosaicked image enhancement method for a single chip CMOS (Complementary Metal Oxide Semiconductor) image sensor which has on-chip ISP (Image Signal Processor) is introduced. CMOS image sensors are becoming popular, because various circuits can be integrated with it into a single chip. In a single chip CMOS image sensor for handheld devices which requires low power consumption, ISP has to be implemented to small size while maintaining the high performance. Demosaicking and image enhancing are the largest blocks in the ISP, because they need some line memories. In this paper, we propose a new method to minimize the number of line memory. In the proposed method, contrast enhancement is done using the buffered data for demosaicking. The green channel is used instead of luminance. Experimental results indicate that the proposed approach enhances the image quality without additional line memories. The proposed method is implemented on FPGA chip in real time mode, and performed successfully.