Hi everyone.I have been presented with a challenge. Our mechanical team have built a machine that randomnly erodes the surface of some test specimen. This is an image of a test specimen captured at the beginning of a test: As you can see four white lines are present in the image, the lines are caused by reflections from the lamps. And this is an image of a similar test specimen at the end of a test. We already have found a satisfying way of measuring the area of the erosion and it seems to be robust for all possible test specimen colors Now they have decided that they want the machine to (online) measure the length of the white reflection lines, as the erosion for some materials only causes the surface to become matted. And does not necessarily give the dark eroded area seen above. an example of such a use case can be seen below: I have tried multiple approaches without the greatest success.ideally I would like to isolate the highlighted lines, so that the system could identify nearly the same lines as the ones that is hand painted below methods tried: 1)IMAQ Find Edge, to get the infinite lines that best describes the highlighted reflection lines.Then using a binning method, the line is segmented, to where there is enough light in the image.this method is however very sensitive to the horizontal variation of the lighting, and will typically either not find the endpoints, or the matted mid section correctly.2)tuning IMAQ Detect Linesgives me this: Which is not exactly what I want as I hoped that the lines left of the eroded area would also be included, and that the lines found above and below the highlights would have been excluded, but getting closer.3)High pass filter the image to enhance the edges, and suppress the effects from the varying light quality.The built in methods had a tendency to enhance the erosion edge more or equal to the highlights, so I tried building my own kernel to only enhance horizontal features, but even with a 5x5 kernel the best result I got was:Which did not exactly let me separate the highlights from the eroded area.4)Finally I tried a cross correlation with an image of a horizontal line with a small width. again I enhanced the eroded area more than the line feature I was interested in.If you have any idea, that I can use to either enhance the highlighted lines, so that the length can be measured I would really appreciate it.I have tried adjusting gamma, contrast, and brightness to make the "white" lines stand more out, but due to the light variation, this also makes the center of the image very bright before the lines are enhanced in the ends. Thank you /ZcuBa

You can very easily find the very top and the bottom line using an Advanced Edge Find function. From there extract the pixel values form the line profile and you should be able to detect any nonuniform pixel values. There is a screen shot of the result. Good luck, Dan

Machine Vision

Measure highlights in image

Solved!

I actually like your method much more than using the Edge Finder.

Just in case you find yourself using the Edge Finder, I would try to adjust the threshold for the Derivative according to the Standard Deviation in the Region of Interest if the lines are the brightest spots in the image. This tends to reduce the issues caused by contrast differences, in most cases I should add. also you can adjust the kernel size and width in order to eliminate false possitives caused by small defects and shadows.

Hope it all works out,

Good luck,

Dan,

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