科研之友
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摘要
The phenotypic traits of corn ear are important quantitative data in maize breeding and variety identification. In tradition, breeding workers are employed to deal with lots of corn ears by means of manual measurement and visual count, however this process is seriously labor-consuming and time-costing, and the measured traits are prone to be subjective and incomplete. In recent years, some semi-automatic systems based on machine vision and image analysis have been developed and applied to the maize variety test, however fully automated test system is still a challenge task owing to the strict high-throughput and high-precision requirements in large-scale maize breeding. To balance efficiency and accuracy of variety test for corn ears, in this paper, a high-throughput phenotypic measurement method and system based on panoramic surface image is proposed. Firstly, a novel mechanic system is proposed, which automatically conveys corn ears above a chain-roller structure, while the rolling corn ears are continuously imaged by a fixed industrial camera that is perpendicular to the moving plane of corn ear. In only several seconds, dozens of side images in which corn ears are in different positions can be collected to generate the image dataset of single corn ear. By analyzing the movement state of corn ear, a transformation model which describes the relationship among ear roll, camera imaging and surface position is then built to bridge the image sequence and the panoramic surface image of corn ear. Corn ears in the image sequence are respectively segmented and the center axes are dynamically determined by figuring out the shape and bounding box. This model always extracts the most appropriate sub regions of corn ear from image sequence, and then stitches them to the calculated positions on the panoramic surface image. As a result, the panoramic image of corn ear demonstrates the three-dimensional surface information in a two-dimensional image, and thus provides more intuitive and complete way for phenotyping calculation of corn ear. The valid surface region of corn ear in the panoramic image is further determined by the boundary detection technique that is performed by evaluating the perimeters of corn ear in the image sequence. Robust kernel segmentation based on hierarchical threshold method is also utilized to extract all candidate kernels which satisfy area and shape constraint, and some more restrictive filters based on machine learning methods, such as SVM (support vector machine), can also be taken to evaluate the validation of kernels. The segmented kernels in the panoramic image are used to calculate the total kernels, number of ear rows and kernels per row. The experimental results show that the proposed method and system can achieve optimized efficiency and accuracy balance. High-throughput convey mechanism improves the efficiency of image acquisition to 15 ears per minute. Compared with the methods based on single and multiple images, the variety test method based on panoramic surface image can make full use of the entire surface information of corn ear and reveal its individual phenotypic traits. The computation accuracies of ear length, ear diameter, number of ear rows, kernels per row and total kernels are up to 99%, 91.84%, 97.15%, 98.89% and 95.37% respectively.
- 出版日期2018
