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融合多目标优化与作物信息占比的自适应三维重建图像获取策略

Adaptive 3D reconstruction image acquisition strategy integrating multi-objective optimization and crop information proportion

  • 摘要: 针对作物多视图三维重建中图像获取参数自适应性不足,重建时长与峰值信噪比难以协同优化,以及输入图像冗余、有效信息利用率低等问题,该研究提出一种融合多目标优化与作物信息占比的自适应图像获取策略。以3个小麦品种全生育期为研究对象,基于多视图采集平台,获取不同株高、幅宽条件下以及不同辅助相机高度、角度和重建图像数量组合下的多视图数据,并开展三维重建试验。首先构建蚁群优化算法(ant colony optimization, ACO)的支持向量回归模型(support vector regression, SVR),预测重建时长(reconstruction time, Time)与峰值信噪比(peak signal-to-noise ratio, PSNR);其次建立双目标优化模型,采用多目标粒子群算法(multi-objective particle swarm optimization,MOPSO)生成非劣解集,并结合逼近理想解排序算法(technique for order preference by similarity to ideal solution,TOPSIS)确定相机高度、角度及重建图像数量等拍摄参数,形成粗策略;最后引入作物信息占比与 Top-K 机制精细化筛选重建图像,形成精策略。结果表明,与均匀采样基准策略相比,粗策略使重建时长缩短42.34%、PSNR提高3.20%;精策略使重建时长缩短44.35%、PSNR提高6.49%,株高和幅宽相对误差分别降低46.44%和36.69%。与粗策略相比,精策略在不增加图像数量和明显计算开销的情况下,PSNR进一步提高3.19%,几何表型重建精度进一步提升。该研究所提策略能够兼顾三维重建效率与质量,可为以小麦为代表的复杂结构作物高通量表型解析中的图像获取提供方法参考。

     

    Abstract: To address the problems of insufficient adaptability of image acquisition parameters, difficulty in simultaneously optimizing reconstruction time and peak signal-to-noise ratio, redundant input images, and low utilization of effective information in crop multi-view three-dimensional reconstruction, this study proposed an adaptive image acquisition strategy integrating multi-objective optimization and crop information proportion. The strategy was designed for wheat three-dimensional reconstruction, aiming to optimize imaging parameters and image screening at the front-end image acquisition stage, reduce redundant inputs, improve the utilization of effective crop information, and enhance reconstruction quality while controlling computational cost. Three wheat cultivars covering the entire growth cycle were used as research objects. Multi-view data were acquired using a multi-view acquisition platform under different plant height and canopy width conditions and different combinations of auxiliary camera height, camera angle, and number of reconstruction images, followed by three-dimensional reconstruction experiments. Wheat plant height, canopy width, auxiliary camera height, auxiliary camera angle, and the number of reconstruction images were used as input variables, while reconstruction time and peak signal-to-noise ratio were used as output variables. An ant colony optimization (ACO)-based support vector regression (SVR) prediction model was constructed to predict reconstruction time (Time) and peak signal-to-noise ratio (PSNR) and to characterize the nonlinear relationship among crop morphological parameters, imaging parameters, and reconstruction performance. On this basis, a bi-objective optimization model was established with the objectives of minimizing reconstruction time and maximizing PSNR. A multi-objective particle swarm optimization (MOPSO) algorithm was used to generate a non-dominated solution set, and the technique for order preference by similarity to ideal solution (TOPSIS) was combined to determine auxiliary camera height, auxiliary camera angle, and the number of reconstruction images from the candidate solutions, thereby forming a coarse strategy to achieve an initial balance between reconstruction efficiency and quality. Considering that the coarse strategy only determined macroscopic imaging parameters and image quantity but could not further evaluate the effective crop information contained in individual images, crop information proportion was further introduced as a quantitative indicator of effective image information. Combined with a Top-K mechanism, images with higher crop information proportion were selected within different views and angular intervals, thereby forming a precision strategy. This strategy further screened effective reconstruction images while maintaining the original multi-view distribution, thereby achieving progressive optimization from imaging parameter optimization to image information screening. The results showed that, compared with the uniform sampling baseline strategy, the coarse strategy reduced reconstruction time by 42.34% on average and increased PSNR by 3.20% on average. Compared with the same baseline strategy, the precision strategy reduced reconstruction time by 44.35% on average and increased PSNR by 6.49% on average, while reducing the relative errors of plant height and canopy width by 46.44% and 36.69%, respectively. Compared with the coarse strategy, the precision strategy further increased PSNR by 3.19% without increasing the number of input images or noticeably increasing computational overhead, and further improved the reconstruction accuracy of geometric phenotypic traits. These results indicated that the coarse strategy reduced redundant image inputs through joint optimization of imaging parameters and image quantity, whereas the precision strategy further improved the utilization of effective crop information through image screening. The proposed strategy can balance three-dimensional reconstruction efficiency and quality and provide a methodological reference for image acquisition in high-throughput phenotyping of complex-structured crops represented by wheat.

     

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