Experimental Study of Subjective Evaluation on Optimal Compression Ratio of JPEG and JPEG2000

Subjective evaluation of compressed image quality on computer displays was studied,in order to realize quality evaluation of compressed images on the Internet.The relative studies include: to set-up displays,to put forward assessment scales for static compressed images based on the standard of subjective assessment of quality for color TV pictures,and to collect color images and establish a database for subjective evaluation.As an example for testing above studies,by using a psychophysical method of pairwise comparison,subjective evaluation experiments on optimal compression ratio of JPEG and JPEG2000 were conducted on displays for the images,which were from JPEG and lossy JPEG2000 with seven compression ratios.Ten subjects took part in the experiments,and 280 color images for 20 scenes with different contents were used.The experimental results showed that optimal compression ratio range of JPEG is from 20∶1 to 25∶1,and optimal compression ratio range of JPEG2000 is from 25∶1 to 30∶1.The experiments indicated that the display set-up by human eyes can achieve consistency for subjective evaluation of image quality on displays.