A Study on JPEG Compression in Color Retinal Image using BT.601 and BT.709 Standards: Image Quality Assessment vs. File Size

摘要

In Indonesia, the prevalence of blindness is about 3%. To overcome the limited communication bandwidth issue in the remote area, utilization of smartphone as teleophthalmology system could be the solution to improve the healthcare services. The image compression is necessary to handle large-size and high-resolution image in the data transmission. The image file size is necessary to be reduced to address several key components in telemedicine, i.e. capable to transmit the image from the remote area and communicate with the coordinating center. Nowadays, several mobile applications have been developed to process the medical image. Furthermore, image compression is required to speed-up the processing task in mobile applications due to the computing power in mobile devices. In this study, the trade-off due to image compression, i.e., between image quality and the image size is investigated. Several asymmetric JPEG quality factors will be applied in R, G, and B channels of the color retinal image. Even though BT. 601 and BT. 709 have the same Q combination, the PSNR, and SSIM in BT. 709 are higher than in BT. 601 due to the weighing factor in G channel for BT. 709 is higher (0.7154) than BT. 601 (0.587). Moreover, the smallest Q combination (50-50-50) in BT. 709 has better performance than the highest Q combination (100-100-100) in BT. 601, in terms of PSNR and file size (93.36 dB and 172 kB vs. 59.93 dB and 2441 kB). Besides, this study has provided further evidence that the G channel in the color retinal image has more information than other channels.