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Graham Convex Hull - edge line

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Graham Convex Hull - edge line

Postby RGulliver » Thu Oct 26, 2017 2:28 pm

Hi Guys,

I am extracting blobs using Graham Convex Hull which is working great for my application. When I find the blob I then Draw a black line to hide about 20mm of the edge, again works very well. What I want to do is extract the blobs twice, one with the black line around the edge and a copy without the black line. Do you have any idea how I can achieve this.

Thanks in advance

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Re: Graham Convex Hull - edge line

Postby andrew.kirillov » Fri Oct 27, 2017 6:59 am


Maybe not exactly what you are looking, but you may try BlobCounter.ExtractBlobsImage(). The thing about this method is that it does not need to be called with the same image, which was used to find blobs. Very often the source image is color. Then it is grayscaled, thresholded, etc. and blobs are found then. But after thresholding, those are just white masks. So after blobs are found, the ExtractBlobsImage() can be used with original color image, so you can extract a blob as it was before processing.

Same in your case - you can extract it once from original image, then draw something on the image and extract the blob again.

However, if you need smaller blob second time (without those borders), you will either need to crop the extracted image or maybe do another round of blob counting.
With best regards,

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Re: Graham Convex Hull - edge line

Postby RGulliver » Fri Oct 27, 2017 8:05 pm

Thanks Andrew will give it a go
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