Nonzero pixels in black image?!

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Steven
Steven on 25 Dec 2013
Commented: Walter Roberson on 25 Dec 2013
In an image process, I have got an image which after being inverted (to calculate the perimeter), it becomes absolutely black on screen. But when I see the pixel values, the last row and column are not zero!
why?
I mean when you sum the pixels, it is not zero!, while the image is completely black!
Thanks!
Steven

Accepted Answer

Walter Roberson
Walter Roberson on 25 Dec 2013
Edited: Walter Roberson on 25 Dec 2013
Your display is not set up to display a color that dark notably differently than true black. This is proper behaviour. Remember, a pixel value of 1 (out of 255) is not very bright.
  3 Comments
Image Analyst
Image Analyst on 25 Dec 2013
Use imwrite to save your binary image and then post it.
Walter Roberson
Walter Roberson on 25 Dec 2013
What is class() of the data ? If it is not "logical" then there are non-zero values that are dark.

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