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I = imread('us-currency.png');
mean = 0.5;
variance = 0.5;
J = imnoise(I,'gaussian', mean, variance);
imshow(J);

What are the effects of mean and variance on that image?

  • Does mean increases the brightness?

  • Does variance increases the amount of noise?

Input

enter image description here

Output

enter image description here

user366312
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1 Answers1

1

The mean and variance set which distribution the random values will taken from.

Once you add those numbers to an image you change the image properties as well.
If the image mean value is imageMeanVal, assuming the image is large, then after the addition of the random noise its mean value will be `imageMeanVal + noiseMeanVal' since the image and the noise are independent.

If you define the brightness of an image as its mean value then you're right, the mean value changes (Increase or decrease) the image brightness.

The same logic holds for the Variance / Standard Deviation.

Yet it is hard to say what's Variance of an image is.
Sometimes one could say it is the power of data in the image and the variance of the noise is the power of noise.
Hence if you increase the power of the added noise, if one looks on the power ration of the image to the noise, you decrease it and makes the data in the image harder to notice.

This is basically the SNR of the noised image.

Royi
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