CODEWITHSUNDEEP
imagealgorithmmatlabimage-processingresampling
user2521180
user2521180

Reputation: 11

Image upsampling in MATLAB producing white images using image() and imshow()

When I display my reconstructed images, they are just white. Is there something obviously wrong with my program?

The reconstructed images should have the values of the downsampled image at one pixel in the upsampled 2x2 pixel block. The interpolation method I'm using here is simply taking the value from one row above and filling the next row with it, repeating this process for the columns.

%% Image Resampling

close all; clear all; clc;

s_dir=pwd;
cd Images;

I=imread('aivazovsky78g.tif','tif');

cd(s_dir)

[N M]=size(I);

figure;
imshow(I)
axis image; hold on;

 for k=1:4
     pause(1)
     I=I(1:2:N, 1:2:M);
     [N M]=size(I);
     image(I)
 end

 %% Image Reconstruction

Irec=zeros(2*size(I));
for r=1:5
for n=1:N-1
    for m=1:M-1
        Irec(2*n-1,2*m-1)=I(n,m);
    end
end
[N M]=size(Irec);
for n=2:2:N
    for m=2:2:M
    Irec(n,:)=Irec(n-1,:);
    Irec(:,m)=Irec(:,m-1);
    end
end
I=Irec;
figure;
imshow(I)
 end

Upvotes: 1

Views: 1896

Answers (2)

Amro
Amro

Reputation: 124563

Not the most efficient way, but here is a working code:

% 256x256 grayscale image
I = imread('cameraman.tif');

% double in size
I2 = zeros(2*size(I),class(I));
for i=1:2:size(I2,1)
    for j=1:2:size(I2,2)
        I2([i i+1],[j j+1]) = I((i-1)/2 + 1, (j-1)/2 + 1);
    end
end

% compare against @Magla's solution
I3 = imresize(I,2,'box');
isequal(I2,I3)

Upvotes: 0

marsei
marsei

Reputation: 7751

You may use B = imresize(A, scale, 'box') where a scale of 2 doubles the amount of pixels in x and y. The z dimension will still have the same value.

The resizing method box will copy the initial pixel value (i, j) to its 3 new neighbors (i+1, j), (i, j+1), and (i+1, j+1) - the same method you programmed.

Upvotes: 0

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