Tahitian pearls are globally known for their luster, rainbow-like color palette, and various shapes. As pearl trading is French Polynesia’s second-largest revenue source after tourism, the manual classification remains labor-intensive, with shape evaluation consuming 60–70% of the expert workload. Furthermore, subtle shape variations make evaluation subjective, often requiring multiple experts to ensure consistency, increasing costs and time. This study introduces a scalable, automated pipeline for pearl shape classification. The system integrates a mirror-based multi-view imaging setup to capture comprehensive views, YOLOv8n for precise object detection, and SAM for segmentation. Discriminative handcrafted features are selected through NSGA-II and combined to enhance classification performance. XGBoost performs a two-step hierarchical classification using selected discriminative handcrafted features. First, pearls are categorized into broad classes (asymmetric, circled, symmetric), then the classification of symmetric pearls is refined into sub-classes like button, oval, etc. Trained on a dataset of 3,929 pearls labeled by five experts, the system achieves weighted F1 scores of 95% and 75% for steps one and two, respectively. Multi-view data was proven crucial for capturing subtle shape variations, particularly for the fine-grained step two classification. Compared to deep-learning-based models, the pipeline demonstrates superior cross-validation stability and accuracy. This framework provides a scalable and objective solution for pearl classification, significantly reducing expert workload while improving consistency. Beyond pearls, the methodology could be used for other applications, such as jewelry or gemstone assessment.

错误:搜索内容不能为空,请输入英文关键词
错误:关键词超出字数限制,请精简
高级检索

Towards an Automatic Shape Classification of Tahitian Pearls

  • Bryan Dallest,
  • Sébastien Chabrier,
  • Alban Gabillon

摘要

Tahitian pearls are globally known for their luster, rainbow-like color palette, and various shapes. As pearl trading is French Polynesia’s second-largest revenue source after tourism, the manual classification remains labor-intensive, with shape evaluation consuming 60–70% of the expert workload. Furthermore, subtle shape variations make evaluation subjective, often requiring multiple experts to ensure consistency, increasing costs and time. This study introduces a scalable, automated pipeline for pearl shape classification. The system integrates a mirror-based multi-view imaging setup to capture comprehensive views, YOLOv8n for precise object detection, and SAM for segmentation. Discriminative handcrafted features are selected through NSGA-II and combined to enhance classification performance. XGBoost performs a two-step hierarchical classification using selected discriminative handcrafted features. First, pearls are categorized into broad classes (asymmetric, circled, symmetric), then the classification of symmetric pearls is refined into sub-classes like button, oval, etc. Trained on a dataset of 3,929 pearls labeled by five experts, the system achieves weighted F1 scores of 95% and 75% for steps one and two, respectively. Multi-view data was proven crucial for capturing subtle shape variations, particularly for the fine-grained step two classification. Compared to deep-learning-based models, the pipeline demonstrates superior cross-validation stability and accuracy. This framework provides a scalable and objective solution for pearl classification, significantly reducing expert workload while improving consistency. Beyond pearls, the methodology could be used for other applications, such as jewelry or gemstone assessment.