Image Stitching And Multi-Resolution Display For Large-Scale Underwater Scene

Underwater exploration is beneficial to the development and utilization of underwater resources.Among them,vision technology plays an important role and cannot be replaced in deep-sea research.Due to the limitation of seabed imaging environment,autonomous underwater vehicle can only take photos close to the seabed.Such a single image can only provide small-scale(such as2 m × 2m)and high-resolution seabed scene information.In the practical application of underwater exploration,the exploration range usually reaches thousands to hundreds of thousands of square meters,so thousands or even tens of thousands of high-resolution original images need to be taken.In order to observe large-scale scene,these images usually need to be stitched together,so that the resolution of underwater panoramic mosaic will be as high as tens of billions of pixels.However,due to the limitations of commonly used computer software and hardware,it is difficult to load all the original images into the memory,so the overall stitching can’t be achieved,and the general image display software can’t display such a large image.In this thesis,image stitching technology and multi-resolution display of large-scale underwater scene are studied,and a special super-large underwater image multi-resolution display system is developed.The main work is as follows:(1)Research and implementation of large-scale underwater image block stitching technology.Firstly,the classical image registration method is used to align all images,and then the block fusion strategy is used to realize the block fusion of panoramic mosaic images.Due to the limitation of hardware conditions on common computers,it is unrealistic to adopt overall fusion.According to the relevant data obtained in the registration stage,this thesis selects only some images for fusion each time,and obtains tens of thousands of image blocks of the same size.These image blocks can be laid and organized without overlap and gap,so as to logically complete the drawing of underwater panorama,and solve the problem of computer memory limitation in the fusion process.In addition,these image blocks,as the subsequent display work source data,can be directly used to construct the multi-resolution display model.(2)Research on super large underwater photo-mosaics display based on dynamic nested double pyramid model.The main problem of the traditional large image display technology based on tile pyramid model is the phenomenon of discontinuous image transition and significant picture jump when switching between different resolutions.To solve the problem,a new dynamic nested double pyramid model is proposed in this thesis.With this model,when the size of the same map is changed,the level difference of the improved model is delayed from the original level one to level two,the change rate of tile number and the field of view coverage are reduced to 0.5 times of the original,and the visual image transition is more continuous.The experimental results verify the effectiveness of the model.(3)Development and implementation of super large underwater photo-mosaics multi-resolution display system.Based on the theory of dynamic nested double pyramid model,a super large underwater image multi-resolution display system composed of three modules: original pyramid model construction,image multi-resolution display and image hierarchical visualization is developed.Among them,model construction module is the basis of image multi-resolution display and hierarchical visualization.Based on the source data obtained by underwater image block stitching technology,a multi-layer dynamic nested double pyramid model is constructed.The image multi-resolution display module meets the viewing needs of users through the interactive graphical user interface,and uses Redis cache technology to improve the update speed of images.The image hierarchical visualization module uses multi-threading technology to quickly visualize the original pyramid model in the database to the local disk.The system has important application value for underwater image observation and resource exploration.The results show that the system runs stably and has good performance.The system expected to better serve the field of seabed exploration in China by further improvement.