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Thread: How to get the noise only image?

  1. #1
    tjucruiser
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    How to get the noise only image?

    Under the same circumstances, I get 15 X ray images I1, I2, I3, ,I15.
    Then two methods were used to get the noise only image.

    First method:
    Noise image=(I1-I2)/sqrt(2).
    They said that subvided by sqrt(2) can maintain the variance of the Noise image identical to I1 and I2.

    Second method:
    Noise image=I1-(I1+I2+I3++I15)/15. Can this method maintain the variance of noise image identical to original images?

    If I don't consider the coefficient of sqrt(2), I think first method can also be explained as
    Noise image=I1-(I1+I2)/2.
    The above equation is similar to second method.

    Please give me some suggestion, Thank you.

  2. #2
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    Re: How to get the noise only image?

    Are the images identical differing only in random noise?
    Or are they different with fixed noise?

  3. #3
    tjucruiser
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    Re: How to get the noise only image?

    The images identical differing only in random noise.

  4. #4
    Senior Member Lars's Avatar
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    Re: How to get the noise only image?

    since noise varies between images I'd be inclined to calc a mean from all images and then diff each image to the mean.
    Monochrome: http://mochro.com

  5. #5
    tjucruiser
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    Re: How to get the noise only image?

    Lars Vinberg, thank you! I think you are right. But can you give me the mathematical deduction. If I have N images with radom noise, and I have them added on, I can eliminate the radom off from the image.

  6. #6
    Senior Member Lars's Avatar
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    Re: How to get the noise only image?

    You can average out noise, not eliminate.

    mean = (I1 + I2 +... + I15) / 15

    That's the best you can do using mean, I think.

    If you want to get into denoising raster algorithms, that's a different thing.
    Monochrome: http://mochro.com

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