Error using ISWT2 " Index exceeds matrix dimensions. Error in iswt2 (line 127) , tmp{j} = reconsLOC(a(:,:,j ),h(:,:,j,​:),v(:,:,j​,:),d(:,: ,j,:));"

Hi I am trying to perform a simple inverse stationary wavelet transform using the code below but i get the following error

Index exceeds matrix dimensions.
Error in iswt2 (line 127),  tmp{j} = reconsLOC(a(:,:,j),h(:,:,j,:),v(:,:,j,:),d(:,:,j,:));

Code

[A,H,V,D] = swt2(i,2,'sym4');

y = iswt2(A,H,V,D,'sym4'); % this function gives the error%

All the size of the coefficient is same as the input so how can index exceed the matrix dimension.

the size of i(input image) is 512x512 unit 16

size 0f A = 512x512x2 single

size of H = 512x512x2 single

size of D = 512x512x2 single

size of V = 512x512x2 single

Answer 1

[Image Analyst]

a,h,d,v are different from A,H,D,V since MATLAB is case sensitive. A,H,D,V are all 3D matrices according to you.

a(:,:,j),h(:,:,j,:),v(:,:,j,:),d(:,:,j,:) are a 3-D, 4-D, 4-D, and 4-D matrix. Plus if you specify an index other than that last one, you will not extract a 3-D matrix. For example h(:,:,j,:) is a 512x512x1xN 4-D matrix, NOT a 3-D matrix. You might need to use squeeze() on the 4-D matrices.

[Akshra]

Hi thank you for suggesting the squeeze function but when I used the squeeze() function I still get the same error unless I am using the squeeze() function incorrectly.

Here is the change I made

H = squeeze(A);

D = squeeze(A);

V = squeeze(A);

y = iswt2(A,H,V,D,'sym4'); %still gives the same error%

Index exceeds matrix dimensions.

Error in iswt2 (line 127) tmp{j} = reconsLOC(a(:,:,j),h(:,:,j,:),v(:,:,j,:),d(:,:,j,:));

[Image Analyst]

reconsLOC is still being passed both 3D and 4-D arrays. You did not use squeeze on j, v, or d in

 tmp{j} = reconsLOC(a(:,:,j),h(:,:,j,:),v(:,:,j,:),d(:,:,j,:));

[Akshra]

Hi I don't think it is possible to squeeze the values j,v,d because they are inbuilt Matlab variables for iswt2 function so I don't think you can alter them.

when i tried to squeeze() h, this what i get

reconsLOC(h(:,:,j,:)) = squeeze(a);

Undefined function or variable 'a'

Did you mean: >> reconsLOC(h(:,:,j,:)) = squeeze(A);

[Image Analyst]

I don't have the wavelet toolbox. Is reconsLOC() your function or theirs?

[Akshra]

its not my function , its Matlab inbuilt function

[Image Analyst]

I don't know - call tech support.

Answer 2

[Walter Roberson]

iswt2() is broken for reconstructing data that was originally grayscale and not of data type double. RGB non-double is okay, and grayscale double is okay, but not (for example) grayscale uint8, or grayscale single.

See https://www.mathworks.com/matlabcentral/answers/340192-why-does-iswt2-r2017a-fail-for-coefficients-in-single-precision