Due to performance and low complexity, JPEG-LS become the standard of lossless and near-lossless image compression. However, it can’t accurately control code rate when it is applied in near-lossless compression. This paper is thus devoted to rate control for near-lossless image compression with JPEG-LS. A model of coding bit-rate under a high bit-rate with respect to mean absolute difference (MAD) and coding quantization parameters for prediction coding is first proposed. Then a rate control method for near-lossless compression is designed based on the model for JPEG-LS. In the process of a specific image coding, to control the bit-rate, quantitative parameters are adjusted piecewise based on the model. Experiments show that the proposed method can make final code rate close to a preset rate. It’s different from other methods that quantitative parameter fluctuating within a wide range can be avoided because of the accurate model of bit-rate. As a result, the proposed control method can achieve approximate optimal rate-distortion performance.
Disparity compensation (DC) and transform coding are incorporated into a hybrid coding to reduce the code-rate of multiview images. However, occlusion and inaccurate disparity estimations (DE) impair the performance of DC, especially in spaceborne images. This paper proposes an adaptive disparity-compensation scheme for the compression of spaceborne multiview images, including stereo image pairs and three-line-scanner images. DC with adaptive loop filter is used to remove redundancy between reference images and target images and a wavelet-based coding method is used to encode reference images and residue images. In occlusion regions, the DC efficiency may be poor because no interview correlation exists. A rate-distortion optimization method is thus designed to select the best prediction mode for local regions. Experimental results show that the proposed scheme can provide significant coding gain compared with some other similar coding schemes, and the time complexity is also competitive.
Lung respiratory movement can cause errors in the operation of image navigation surgery and they are the main errors in the navigation system. To solve this problem, the image-based motion correction strategy should be proposed to quickly correct the respiratory motion in the image sequence. So, the commercial ultrasound machine can display contrast and tissue images simultaneously. In the paper, a convenient, simple and easy-to-use breathing model whose precision was close to the sub-voxel was proposed. The first, in the clinical case the low gray-level variation in the tissue images, motion parameters were first calculated according to the actual lung movement information of each point the tissue images are registered by using template matching with sum of absolute differences metric. Finally, the similar images are selected by a double-selection method which requires global and local threshold setting. The generic breathing model was constructed based on all the sample data. The results of experiments show the algorithm can reduce the original errors caused by breath movement heavily.
Calculation of ultrasonic field based on medical transducers is often done by applying acoustics and using the Tupholestetpanishen method of calculation. The calculation is based on spatial impulse response; the spatial impulse response has only been determined analytical for a few geometries and using apodization over the transducer surface generally make its impossible to find the response analytically. A popular approach to find the general field is thus to split the aperture into small rectangles, and then sum the weighted response from each of these. The problem with triangular is their poor fit apertures which do not have straight edges, such as circular and oval shapes. In order to solve the problem, a novel algorithm based on triangular be proposed in the paper, the simulation of ultrasonic field based on the algorithm can be improved obviously.