What is a Bounding Box?
A bounding box is a rectangular region defined by coordinates that encloses an object, face, text area, or other feature. It may be axis-aligned or rotated, depending on the representation.
How Bounding Boxes work
Detection and annotation systems express a box through corner coordinates, an origin plus dimensions, or a center, size, and angle. The rectangle is usually carried alongside a class, confidence score, or tracking identifier and must be transformed whenever an image is resized, cropped, padded, or rotated. In computer-vision workflows it provides inexpensive localization, while masks or polygons preserve the contours needed for compositing and pixel-level measurement.
Key facts
- 1Coordinate conventions are not interchangeable: values may be pixels or normalized fractions, and right or bottom edges may be inclusive or exclusive. An undocumented convention causes off-by-one errors.
- 2Intersection over union divides the area where two boxes overlap by the area of their union, and is commonly used for detection matching, suppression, and evaluation without inspecting object pixels.
- 3For a planar point set, a minimum-area enclosing rectangle can be found from its convex hull; allowing rotation can produce a substantially tighter result than an axis-aligned box.
When Bounding Boxes matter
Use bounding boxes to report detections, guide crops, place annotations, or limit regional processing. They include background around nonrectangular subjects, so precise segmentation may require a mask.