基于高动态范围成像的温室番茄植株图像色彩矫正方法
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国家自然科学基金项目(61703048)、北京市农林科学院青年科研基金项目(QNJJ201722)和江苏大学农业装备学部项目(4111680002)


Image Color Correction Method for Greenhouse Tomato Plant Based on HDR Imaging
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    摘要:

    针对温室番茄智能化管理视觉信息稳定获取的需要,研究了基于高动态范围成像技术的番茄植株图像色彩矫正方法,以克服复杂自然光照条件对作业对象色彩稳定呈现的客观限制。鉴于温室内光照时空波动和复杂背景辐射强度突变导致图像色彩失真,提出了融合多曝光强度图像的摄像机辐射响应模型标定方法;分别提取曝光时间为0.01、0.05、0.08、0.10ms的4幅图像离散像素点的Y通道亮度信息,求解特定视场下像素点亮度与曝光度的函数关系,在此基础上以低曝光度图像亮度为参考,估计摄像机全局视场的辐射强度;采用S曲线函数压缩高动态范围图像数据,将视场辐射强度映射为图像亮度,实现对低曝光图像的色彩矫正重构;最后,通过现场试验对色彩矫正方法进行验证,试验结果表明,不同场景和时段的番茄植株图像的灰度信息量、离散程度和清晰度均得到改善,图像灰度信息熵、标准方差和平均梯度平均提高16.87%、9.81%和19.49%。本研究可为农业复杂光照条件下作业对象图像色彩信息的获取研究提供参考。

    Abstract:

    In order to accurately acquire the tomato plants’ image information under the complex illumination in greenhouse, the method of correcting image color based on high dynamic range (HDR) imaging was researched, which was urgently needed for robotic production in greenhouse. Focused at the color distortion caused from sunlight’s continuous variation and background object’s radiation saltation, the color image’s brightness data was extracted from CIE XYZ color mode. And the camera’s response function was recovered, according to the brightness images with various exposure time of 0.01ms, 0.05ms,0.08ms and 0.10ms. As the HDR image data, the radiation intensity of the view field was estimated based on the response function, referring to the underexposed image’s brightness. The HDR brightness data was compressed into brightness image with grey value range of (0, 255), by the S-shaped mapping function, and then the brightness data was integrated into the underexposed image to reconstruct the image color data. Finally, the color correction method was verified by field test in greenhouse. As the result showed, the method was applicative for improving color quality of images, captured from different scenes under the various sunlight at different time. Specifically, the image’s entropy, standard deviation, and average gradient were averagely raised by 16.87%, 9.81% and 19.49%, respectively, after the original images captured with the serial exposure time were fused, and the color of image captured at different time could keep stable. The research result was supposed as the reference for acquiring object image information under the complex agricultural environment.

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冯青春,王秀,李军辉,李小明,成伟,陈建.基于高动态范围成像的温室番茄植株图像色彩矫正方法[J].农业机械学报,2020,51(11):235-242. FENG Qingchun, WANG Xiu, LI Junhui, LI Xiaoming, CHENG Wei, CHEN Jian. Image Color Correction Method for Greenhouse Tomato Plant Based on HDR Imaging[J]. Transactions of the Chinese Society for Agricultural Machinery,2020,51(11):235-242.

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  • 收稿日期:2020-02-17
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  • 在线发布日期: 2020-11-10
  • 出版日期: 2020-11-25