JPEG2000-based shape adaptive algorithm for the efficient coding of multiple regions-of-interest
The JPEG2000 standard supports two methods to code regions-of-interest (ROIs) in an image-the maxshift method and the scaling-based method. Compared to the maxshift method, the scaling-based method is preferable in many applications because it allows the nonROI (background) region to be partially coded prior to coding all of the ROIs. This is accomplished by supporting arbitrary bitplane shift factors and by filling the most significant bit-planes of the nonROI region with zeros after the ROI bitplanes have been shifted up in value. In both of these methods, the embedded block coding with optimum truncation (EBCOT) algorithm is then applied to code the wavelet coefficients. However, when multiple regions-of-interest need to be coded, the performance of the scaling-based method degrades significantly since the EBCOT coder is no longer able to efficiently code the nonROI region, which is now less contiguous as compared to the single-ROI case. Also, the large header information that is required in JPEG2000 for each ROI degrades the coding performance. This paper presents an improved scaling-based method for the efficient coding of multiple, arbitrarily-shaped ROIs using a modified EBCOT algorithm. The proposed method utilizes the shape information of the different ROIs to generate a stripe mask, which is then used to optimize the coding performance. Coding results and comparisons with the JPEG2000 scaling-based method are presented to illustrate the improved performance of the proposed scheme.