CODEWITHSUNDEEP
matlabimage-processingimage-resizing
Aadnan Farooq A
Aadnan Farooq A

Reputation: 646

Resizing image increases noise?

I want to know that when we resize the image from 30x30 pixels image to 150x150 pixels image using Matlab. Does resizing adds extra noise in the image? Or vice versa case

Upvotes: 0

Views: 728

Answers (1)

Rotem
Rotem

Reputation: 32084

Resize down may increase SNR (if for example, each destination pixel is sum of 2x2 source pixels). Resize up increases blur, but does not suppose to decrease the SNR.

You can make a simple test:
Load a "clean image", create noisy image by adding random Gaussian noise, and measure the SNR.

Example: 

I = im2double(imread('cameraman.tif')); %I is the "clean" image.
J = imnoise(I); %Add noise
N = J - I; %Noise image
r = snr(I, N);

Result: r = 14.84

Resize down: 

I2 = imresize(I, 0.5);
J2 = imresize(J, 0.5);
N2 = J2 - I2;
r2 = snr(I2, N2);

Result: r2 = 22.41 (SNR is improved by about factor of sqrt(2) - theoretical improvement).

Resize up: 

I3 = imresize(I2, 2);
J3 = imresize(J2, 2);
N3 = J3 - I3;
r3 = snr(I3, N3);

Result: r3 = 23.66 (SNR is a about the same)

Upvotes: 2

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