XSET - Emerging Trends in Image Processing, Computer Vision, and Pattern Recognition - page 87

image quality estimators such as: MSSIM [ 11 ] , PSNR [ 12 ] , SSIM [ 13 ] , VIF [ 14 ] , UQI [ 15 ] , and
WSNR [ 16 ] .
FIGURE 3 Process for comparing JPEG2000 and X SET. Given some viewing conditions a
X SET compression is performed obtaining a particular bit-rate. Thus, a JPEG2000 compres-
sion is performed with such a bit-rate.
This experiment is performed across the CMU [ 17 ] and IVC [ 18 ] Image Databases. Image
quality estimations are assessed by the six metrics mentioned before.
Figures 4 and 5 show the perceptual quality, estimated by Figure 4(a) MSSIM, Figure 4(c)
SSIM, Figure 5(a) UQI, Figure 5(b) VIF and Figure 5(c) WSNR, in addition to the objective
quality Figure 4(b) PSNR, of the recovered color images both for JPEG2000 (Blue function;
dark gray in print versions) and XSET (Green function; light gray in print versions) as a func-
tion of their compression rate. For this experiment, we employthe CMU Image Database and
the Kakadu implementation for JPEG2000 compression [ 19 ] . On the average, a color image
compressed at 1.0 bpp (1:24 ratio, stored in 32 kB) by JPEG2000 coder has MSSIM = 0.9424,
SSIM = 0.8149, UQI = 0.5141, VIF = 0.2823 and WSNR = 29.2 of perceptual image quality, and
PSNR = 30.11 of objective image quality, while by XSET has MSSIM = 0.9780, SSIM = 0.8758,
UQI = 0.6249, VIF = 0.4387, WSNR = 35.41 and PSNR = 31.84. In Figure 6 , we can see these dif-
ferences when images (a-b) Lenna , (c-d) Girl2 , and (e-f) Tiffany are compressed at 0.92, 0.54,
and 0.93 bpp, respectively, by JPEG2000 and XSET. For example, for these three images, the
average difference of MSSIM is 0.0321 in favor of XSET. Therefore, for this image database,
XSET has clearly improvement of visual quality than JPEG2000.
FIGURE 4 Comparison between XSET (green functions; light gray in print versions) and
JPEG2000 (blue functions; dark gray in print versions) image coders. Compression rate
versus image quality assessed by (a) MSSIM, (b) PSNR and (c) in the CMU image database.
FIGURE 5 Comparison between XSET (green functions; light gray in print versions) and
JPEG2000 (blue functions; dark gray in print versions) image coders. Compression rate
versus image quality assessed by (a) UQI, (b) VIF, and (c) WSNR in the CMU image data-
base.