How to show only straight line in binary?

Please help me to solve this problem. I just need straight line in the midle as white.

[Andrew Newell]

You'll need to provide more detail.

[muhammad ismail]

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I want to detect scratch on metal surface. This is original image. After I convert this image to binary(BW), it show unwanted shape in that image. So I just need scratch line and want to remove that unwanted shape in binary condition. Really need your help. Thank You.

Answer 1

[Image Analyst]

Several ways. Since the sample seems to be centered, simply crop your image with imcrop.

Another way is to use the whole image but get rid of blobs touching the border with imclearborder() and get rid of small remaining specs with bwareaopen().

Another way is to do a background correction so you don't get that junk in the bottom in the first place. To do that you need to divide your image by an image of a uniform gray sheet.

[muhammad ismail]

Thank you very much. It really helpful.