Title: Fast apple inspection in colour space

Authors: Rory C. Flemmer; Claire L. Flemmer; Michael J. Caulton

Addresses: School of Engineering and Advanced Technology, Massey University, Private Bag 11 222, Palmerston North, 4442, New Zealand ' School of Engineering and Advanced Technology, Massey University, Private Bag 11 222, Palmerston North, 4442, New Zealand ' Compac FHS Ltd., 15 Barnes Place, Hastings, 4175, New Zealand

Abstract: This work presents an apple image library of over 20,000 colour images of four varieties of randomly oriented apples (both mono-coloured and variegated varieties). The image library is offered to other researchers in apple inspection. The images were analysed using a colour difference operator, a grey level difference operator and an islanding routine to identify points of interest that could be calyxes, stems or blemishes. The method correctly identified 98% of calyxes, 93% of stems and 83% of defects. 5% of blemish-free images were mistakenly identified as having defects; the 'ghost islands' arising because the natural variation in the peel colour of variegated apples was sufficiently pronounced to look like a defect. Image processing time is fast enough for implementation in commercial packing lines.

Keywords: apple inspection; stem identification; calyx identification; blemish identification; random orientation; computer vision; visual inspection; automated inspection; apple images; colour difference; apple defects; variegated apples; image processing; commercial packing lines.

DOI: 10.1504/IJPTI.2014.068729

International Journal of Postharvest Technology and Innovation, 2014 Vol.4 No.2/3/4, pp.164 - 177

Received: 30 Dec 2013
Accepted: 03 Dec 2014

Published online: 18 Apr 2015 *

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