access icon free Multi-directional colour edge detector using LQS convolution

© The Institution of Engineering and Technology
Received 22/08/2017, Accepted 03/02/2018, Revised 10/01/2018, Published 09/02/2018

A new linear colour image filter based on linear quaternion systems (LQSs) is introduced. It detects horizontal, vertical, left- and right-diagonal edges with a single LQS convolution mask. The proposed filter is a canonic minimal filter of four LQS filters, each with different angles of rotation combined parallel wise. Different angles of rotation are a key features of the new filter such that horizontal, vertical, left, and right-diagonal LQS filter masks rotate pixels through angles , , , and , respectively. Although, the four LQS masks are combined parallel to make a single LQS mask but derived using four quaternion convolutions, one for each direction of edges, the LQS filter produces a result without the combination of results from four separate edge detectors. This methodology could be generalised to design more elaborate LQS filters to perform other geometric operations on colour image pixels. The proposed filter translates smoothly changing colours to different shades of grey and produces coloured edges in multiple directions, where there is a sudden change of colour in the original image. Another key idea of the proposed filter is that it is linear because it operates in homogeneous coordinates.

Inspec keywords: image filtering; image colour analysis; edge detection

Other keywords: right-diagonal edges; LQS filters; single-LQS convolution mask; vertical-diagonal edges; quaternion convolution; homogeneous coordinates; linear colour image filter; linear quaternion systems; left-diagonal edges; grey shades; colour image pixels; multidirectional colour edge detector; horizontal-diagonal edges; edge direction

Subjects: Image recognition; Filtering methods in signal processing; Computer vision and image processing techniques

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