In this example of edge detection:
http://www.mathworks.com/help/images/edge-detection.html#buh9ylp-13
How would I remove the gray background in the grayscale image at the beginning?
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3your question makes no sense, what do you mean remove? you want it to be opaque or something? – GameOfThrows Jul 07 '16 at 13:00
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that background is not black or unique color – ddb Jul 07 '16 at 13:00
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@GameOfThrows as in make the coins a cutout. When I blend a similar image with another the gray surface the coins sit on is still in the image and I want to remove it. – J.Doe Jul 07 '16 at 13:15
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@ddb sorry changed to gray. – J.Doe Jul 07 '16 at 13:16
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you want to use the edge detection and then write the image as a png file with transparency - this would be the cut out of the coins' edges you want. – GameOfThrows Jul 07 '16 at 13:22
1 Answers
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Removing the background befor you apply an edge detector makes no sense as the more or less homogeneous low frequency background will result in a zero gradient anyway. It won't improve the results of your edgedetection.
If you only want to cut out the coins to put them on a different background simply apply a global threshold
Remove thos tiny speckles with some morphological operators and blur the mask so you won't have fringed coin edges
Apply some logical operations to mask the original image
Piglet
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1Applying a threshold is just using comparison operator (like `<`) and a threshold value. – Jul 07 '16 at 15:07
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Still not sure what to do, I can read in the image with imread, but what do i replace the values with so that they disappear? I can just change the grayscale saturation it looks like. – J.Doe Jul 07 '16 at 15:15
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1@J.Doe do yourself a favour and read a book on image processing fundamentals. you will have a very hard time if you don't have at least some knowledge. knowing how to use google also helps! http://de.mathworks.com/discovery/image-thresholding.html – Piglet Jul 07 '16 at 16:21