Background: The application of exogenous plant growth regulator, for example forchlorfenuron (CPPU), on kiwifruits has become an important factor that influences kiwifruit economic efficiency and the health development of the kiwifruit industry. Owing to the slight difference in calyx shape between the kiwifruits treated with CPPU (CPPU-treated kiwifruits) and the kiwifruits without CPPU treatment (CPPU-untreated kiwifruits), this study aims to provide a cheap, quick, convenient, and non-destructive method for identifying CPPU-treated kiwifruits based on the images of kiwifruits captured at visible lights.
Results: The identification method includes three steps. Firstly, the kiwifruit was extracted from the background by using Otsu algorithm, hole filling operation and 'bwareaopen' function. Secondly, the calyx was extracted by using corrosion, image enhancement, hole filling and closing operations. Finally, the length/width ratio of the minimum enclosing rectangle of calyx region was calculated. The kiwifruit was regarded as a CPPU-treated kiwifruit if the length/width ratio of the rectangle was higher than 1.6. Otherwise, the kiwifruit was regarded as a CPPU-untreated one. The method had the total identification accuracy rate of 90.0% when the kiwifruit images were captured either by utilizing a smartphone at normal lighting condition or by using an image acquisition system.
Conclusion: The programs run on computer and smartphone were developed, and they could realize kiwifruit identification in 0.6 s and 2 s, respectively. The study makes identifying CPPU-treated kiwifruits in online processing be realizable, and offers a convenient method for kiwifruit consumers. © 2019 Society of Chemical Industry.
Keywords: CPPU; calyx; identification; image processing; kiwifruits; machine vision.
© 2019 Society of Chemical Industry.