One-shot semantic segmentation involves training a model to segment objects in images using only a single annotated example of a new class. This approach is useful in scenarios where labeled data is scarce or expensive to obtain, such as medical imaging or specialized industrial applications. The core idea is to enable the model to generalize from minimal data by leveraging prior knowledge from related tasks or classes. For example, a model pre-trained on common objects like cars or trees might adapt to segment a rare bird species using just one annotated image. This is achieved through techniques like meta-learning or transfer learning, where the model learns a flexible feature representation that can quickly adapt to new classes with minimal fine-tuning.
A common technical approach involves using a two-branch architecture, where one branch processes the “support” image (the single annotated example) and the other processes the “query” image (the target to segment). Features from both branches are compared to identify similarities, guiding the segmentation of the query image. For instance, methods like CANet (Class-Agnostic Segmentation Network) extract features from the support image, compute masked average pooling to focus on the target class, and fuse these features with the query image’s features in a decoder to produce the segmentation mask. Another example is PFENet (Prior-Guided Feature Enrichment Network), which uses spatial and semantic prior knowledge from the support image to enhance query image features without requiring iterative fine-tuning. These architectures often rely on distance metrics or attention mechanisms to align features between support and query images, ensuring the model focuses on relevant regions.
Challenges include overfitting to the single example and handling variations in object appearance, scale, or context. To mitigate overfitting, techniques like episodic training simulate multiple one-shot scenarios during training, forcing the model to adapt to diverse tasks. For robustness, some methods augment the support image with synthetic transformations or leverage auxiliary data from base classes. Applications range from medical imaging (e.g., segmenting tumors from a single annotated MRI slice) to robotics (e.g., identifying a new object for manipulation). While current models still struggle with highly complex scenes or ambiguous boundaries, advancements in few-shot learning and feature fusion continue to improve performance. Developers can experiment with frameworks like PyTorch implementations of CANet or PFENet to integrate one-shot segmentation into custom pipelines.