Since the ROI mask expends as it is created, there is a possibility for two ROIs that are disjoint in the spatial domain to have some have some coefficients in common in the wavelet domain.
First, the coefficient bitplanes of all ROIs must be scaled with the same values, which does not have the flexibility to allow for an arbitrary scaling value to define the relative importance of the ROIs and BG wavelet coefficients.
The general scaling based method can offer the multiple ROIs coding with different degrees of interest, but it has three major drawbacks.
At high bit rates, both ROIs and BG can be coded with high quality and the difference among them is not very noticeable.
For multiple ROI coding, GLBShift cannot only support different degrees of interest at different decoding rates, but also dose not limit the ROIs shapes.
Figure 8 shows original and reconstructed MRI images with three ROIs using different ROI coding methods.
Experimental results for medical image show that the presented method can efficiently code multiple ROIs based on different degrees of interest without any shape information of the ROIs.
It also supports for lossless coding of ROIs only or the entire image.