Image Processing Reference
In-Depth Information
FIGURE 9 512 512 pixel Image Lenna from CMU image database with 8 bpp. ROI is a patch
at the center of the image, whose size is 1/16 of the image. Decoded images at 0.34 bpp us-
ing φ = 8 for MaxShift method (a) in JPEG2000 coder and (b) in H i -SET coder, and
BPmask = 1111000110110000 for (c) GBbBShift and (d) ρGBbBShift methods in H i -SET
coder.(a) MaxShift method in JPEG2000 coder, 0.34 bpp. (b) MaxShift method in H i -SET
coder, 0.34 bpp. (c) GBbBShift method in H i -SET coder, 0.34 bpp. (d) ρGBbBShift method in
H i -SET coder, 0.34 bpp.
4.2 Application in Other Image Compression Fields
The usage of ROI coded images depends on an specific application, but in some fields such as
manipulation and transmission of images is important to enhance the image quality of some
areas and to reduce it in others [ 14 , 15 ] . In telemedicine or in remote sensing (RS) it is desirable
to maintain the best quality of the ROI area, preserving relevant information of BG, namely,
the most perceptual frequencies.
Thus, in medical applications an image is by itself an ROI ϕ area of the human body, a mam-
mography is an area of chest, for instance. That is why, it is important to know where is this
ROI ϕ located, in order to ease the interpretation of a given ROI coded image. In addition, ac-
cording Federal laws in some countries, ROI areas must be lossless areas [ 16 ] . ρGBbBShift is
able to accomplish these two features.
Figure 10 shows an example of medical application. A rectangular ROI of the Image mdb202
from PEIPA image database [ 17 ] , coordinates [120 440 376 696], is coded at 0.12 bpp by
JPEG2000 and H i -SET, employing MaxShift and ρGBbBShift methods, respectively. The over-
all image quality measured by PSNR in Figure 10(a) (MaxShift method applied to JPEG2000)
is 37.21 dB, while in Figure 10(c) (ρGBbBShift method applied to H i -SET) is 36.76 dB. Again,
PSNR does not reflect perceptual differences between images ( Figure 10(b) and (d) ). When
perceptual metrics assess the image quality of the ρGBbBShift coded image, for example,
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