Image segmentation is a computer vision task that involves dividing an image into multiple segments or regions based on certain criteria, such as color, intensity, texture, or other visual properties. The goal of image segmentation is to extract meaningful and semantically coherent regions from an image, which can then be used for further analysis, object detection, tracking, or understanding the scene's content.
Unlike image classification where the entire image is assigned a single label, image segmentation assigns labels to individual pixels or groups of pixels, effectively creating a pixel-wise mapping of the image.
There are several approaches to image segmentation, including:
Thresholding: Simplest approach involving setting pixel intensity thresholds to create binary masks. This is often used for basic tasks like separating objects from the background.
Region-based Segmentation: Dividing the image into regions with similar properties, using techniques like region growing or watershed segmentation.
Edge Detection: Identifying edges and contours in an image using techniques like the Canny edge detector and then grouping edges into segments.
Clustering: Grouping similar pixels into clusters based on color, texture, or other features using algorithms like k-means clustering.
Graph-based Methods: Treating pixels as nodes in a graph and forming segments by defining connections (edges) between neighboring pixels.
Deep Learning: Utilizing neural networks, especially convolutional neural networks (CNNs), to learn complex patterns for image segmentation. Fully Convolutional Networks (FCNs), U-Net, and Mask R-CNN are popular architectures.
Semantic Segmentation: In semantic segmentation, each pixel is labeled with a class category. This is often used for tasks like identifying objects and their boundaries within an image.
Instance Segmentation: This type of segmentation goes a step further and not only labels each pixel with a class but also distinguishes between different instances of the same class. It's useful for scenarios where multiple instances of an object need to be individually identified.
Panoptic Segmentation: This is a combination of semantic and instance segmentation, aiming to label every pixel with a class and instance ID, even in cases where instances of the same class overlap.
Image segmentation has a wide range of applications, including medical image analysis, autonomous driving (lane detection, object detection), satellite imagery analysis, object tracking, and more. It's a challenging task due to the complexity of scenes and the need for high-level understanding of image content. Deep learning techniques have significantly improved the accuracy and robustness of image segmentation methods in recent years.