imaging and machine vision europe october/november 2011
www.imveurope.com
image processing libraries
Ease of use Leaving aside all these arguments for purchasing a commercial imaging library, a big attraction of the standard imaging library is that the user doesn’t necessarily need to do any programming. ‘The majority of users are not experts in vision and need an imaging library that’s intuitive enough to use without having an academic degree in vision,’ comments Arnaud Lina, manager processing team, analysis tools at Matrox Imaging. ‘The complexity and number of parameters involved in optimising a particular solution must be kept to a minimum. This is something that vision library manufacturers are working on; the pure black box with one button to press is not yet a reality.’ Software environments like Matrox’s Design Assistant allow the engineer to program a vision system using a graphical interface. The engineer builds algorithms using building blocks; the steps are configured and linked graphically without having to write any code. ‘Simplifying the image processing concepts
– masking all the image processing, signal processing, and computer vision concepts – is not easy to do,’ states Lina. ‘We’ve worked hard to put a layer in between the user and
the underlying mathematics and make the parameters intuitive. We’ve added a layer of heuristics or combinations of mathematics to translate the maths to visual concepts. Some concepts are very easy to map – a scale is a scale, a translation is a translation, a rotation is a rotation. But how smooth a filter is, or how much a filter will denote an image, is more complex.’ He adds that some parameters
‘In general, the algorithms are getting more and more complicated. There are more parameters to consider’
are too complex to control manually and the software is programmed to automatically determine a value based on the image rather than the user setting the parameter. Making imaging software easier to use is something Dr Eckstein also feels is important. ‘In general, the algorithms are getting more and more complicated,’ he says. ‘There are more parameters to consider – even the relatively straightforward task of pattern matching requires the user to specify multiple
parameters, such as rotation angle, scaling, invariance to perspective distortion, etc. This is difficult for many customers.’ Halcon provides algorithms in which parameters can be trained automatically using sample images. ‘You increase robustness and speed of image processing just by showing example images,’ Dr Eckstein says. Data code reading, OCR, and defect classification are areas benefitting from automatic parameterisation within the software. Dr Eckstein also recognises that an end
user might want to be able to tune parameters themselves and considers both manual and automatic parameterisation important. ‘Some parameters are known and can be specified manually,’ he says. ‘However, automatically training the system is more convenient for certain tasks. It also depends on the customer: end users and integrators prefer automatic training, while an OEM wants to get the best performance and robustness and so they might fine-tune their parameters.’ There are also different software
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environments available, depending on the knowledge of the engineer. Generally, companies with more standard tasks, such as OCR, barcode reading, or blob analysis, would
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