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摘要: 优化截断嵌入式编码(Embedded block coding with optimized truncation, EBCOT)是JPEG 2000的核心, EBCOT所采用的基于码块的率失真优化方式为实现图像感兴趣区(Region of interest, ROI)编码提供了良好的基础. 本文分析了其中具有代表性的隐式ROI 编码算法, 并提出了一种改进方法. 通过构造加权函数, 合理地为ROI码块分配权重, 在保证ROI信息被优先编码的同时, 降低ROI码块中背景区域小波系数的影响, 提高了重建图像ROI的质量. 实验结果表明, 算法在低码率下重建图像ROI质量提高明显, 在高码率下也能够很好兼顾重建图像背景区域的质量.Abstract: Embedded block coding with optimized truncation (EBCOT) is the core of JPEG 2000. The usage of rate-distortion optimization in EBCOT provides a good foundation for the realization of region of interest (ROI) image coding. This paper analyzed the representative approach of the implicit ROI coding algorithms and proposed an improved method. By constructing a weighted function and giving reasonable weight for ROI code block, and by reducing the wavelet coefficients effect on the context region of the ROI code block while ensuring the ROI information to be encoded with high priority at the same time, the proposed method improved the quality of the reconstructed image of ROI. Experimental results showed that the reconstructed ROI image quality is significantly improved under low bit rate and that under high bit rate, the reconstructed image background quality can be improved too.
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