Legacy ImageMagick Discussions Archive

am working on automated system for defect detection in ceramic tiles and their classification. I am using matlab. Help is needed, how should I start? I need to detect blobs,pinholes,cracks,pattern etc.

I am a second year EE student, so this should be kept in mind while explaining.

That's a very wide question. I would tackle it like this.

1. Define the terms. For example: what visually defines a pinhole? What distinguishes a pinhole from any other defect or feature? Ideally, each definition will capture all occurrences of the defect, without incorrectly declaring a defect where this isn't one. In other words, no false negatives or false positives.

2. Decide on the outputs. Perhaps this is a mask for every tile, white where there is a defect, and otherwise black. Or perhaps types of defects should be shown in different colours. Or perhaps the output is a simple accept/reject for each tile, according to some criteria.

3. Implement steps (1) and (2). When you do this, and test on a range of inputs, you'll probably discover you need to refine your definitions.

An initial definition of a pinhole might be: "a small roughly circular patch where the lightness is significantly darker than surrounding pixels," with suitable definitions of "small" and "significantly".

That definition could be implemented as a blur and threshold, followed by a search for black pixels surrounded by 8 white neighbours. ImageMagick operations for this might be "-blur", "-threshold" and "-morphology HMT".

I can't help with Matlab. I expect there are Matlab forums somewhere.