class HaarCascade – Feature Descriptor

The Haar Cascade feature descriptor is an opaque handle used by Image.find_features() to run Viola-Jones object detection on an image. It holds the multi-stage classifier produced by training a Haar feature cascade (for example, the built-in "frontalface" and "eye" cascades, or a binary cascade file loaded from disk).

Cascade objects are created via the image.HaarCascade() factory function; there is no public constructor. Once created, the cascade is passed directly to Image.find_features() and the same cascade may be reused across many frames.

The underlying class is Cascade. Its repr() shows the window size and the number of stages, features, and rectangles in the cascade, e.g.:

>>> print(image.HaarCascade("frontalface"))
{"width":25, "height":25, "n_stages":25, "n_features":2913, "n_rectangles":6383}

class image.Cascade

Opaque cascade handle returned by image.HaarCascade(). The instance has no public methods or attributes – it can only be passed to Image.find_features().