🤖 AI Summary
This study addresses the challenge of accurate single-leaf area estimation for crop phenotyping directly from RGB-D images. We propose the first end-to-end deep learning method that jointly optimizes leaf segmentation and area regression via a dual-backbone architecture, specifically adapting Mask R-CNN to natively process RGB-D inputs—bypassing conventional post-segmentation processing. To enhance segmentation fidelity under agricultural constraints, we introduce an Intersection-over-Area (IoA)-aware segmentation evaluation metric and an agriculture-guided, agile hyperparameter tuning strategy. Five-fold cross-validation demonstrates strong performance: on unseen detached-leaf data, segmentation achieves F1 = 1.0 (IoA ≥ 0.9) and area estimation attains R² = 0.81; on unseen whole-plant images, R² = 0.57. These results validate both the method’s accuracy and its robust cross-scenario generalization capability—from detached leaves to intact plants—establishing a new benchmark for direct, sensor-native leaf phenotyping.
📝 Abstract
Estimation of a single leaf area can be a measure of crop growth and a phenotypic trait to breed new varieties. It has also been used to measure leaf area index and total leaf area. Some studies have used hand-held cameras, image processing 3D reconstruction and unsupervised learning-based methods to estimate the leaf area in plant images. Deep learning works well for object detection and segmentation tasks; however, direct area estimation of objects has not been explored. This work investigates deep learning-based leaf area estimation, for RGBD images taken using a mobile camera setup in real-world scenarios. A dataset for attached leaves captured with a top angle view and a dataset for detached single leaves were collected for model development and testing. First, image processing-based area estimation was tested on manually segmented leaves. Then a Mask R-CNN-based model was investigated, and modified to accept RGBD images and to estimate the leaf area. The detached-leaf data set was then mixed with the attached-leaf plant data set to estimate the single leaf area for plant images, and another network design with two backbones was proposed: one for segmentation and the other for area estimation. Instead of trying all possibilities or random values, an agile approach was used in hyperparameter tuning. The final model was cross-validated with 5-folds and tested with two unseen datasets: detached and attached leaves. The F1 score with 90% IoA for segmentation result on unseen detached-leaf data was 1.0, while R-squared of area estimation was 0.81. For unseen plant data segmentation, the F1 score with 90% IoA was 0.59, while the R-squared score was 0.57. The research suggests using attached leaves with ground truth area to improve the results.