How to define variable names for resampling?

I am using following code to resample the 10m green,red and nir bands to 20m resolution;

% Resample the 10m bands to 20m 
if ismember(files(i + j).name, {'*_B03_10m.jp2', '*_B04_10m.jp2', '*_B08_10m.jp2'})
    img = imresize(img, 0.5, 'Method', 'bilinear');
end

But this part of code is being not executed.

The names of band files are as follows

T43RGN_20210119T053141_B03_10m

T43RGN_20210119T053141_B04_10m

T43RGN_20210119T053141_B05_20m

T43RGN_20210119T053141_B06_20m

T43RGN_20210119T053141_B07_20m

T43RGN_20210119T053141_B08_10m

I request you to kindly suggest me how to execute above mentioned part of code also.

Deva

Answer 1

[Stephen23]

You should:

• replace the ISMEMBER with ENDSWITH
• get rid of those asterisks

For example:

endsWith(files(i+j).name, {'_B03_10m.jp2', '_B04_10m.jp2', '_B08_10m.jp2'})

or even simply:

endsWith(files(i+j).name, '_10m.jp2')

You might also like to use the IgnoreCase option.

NOTE: your code does not work because ISMEMBER matches text literally, so what you incorrectly think are wildcard characters that match anything are in fact literal asterisk characters that match... the asterisk character. The ISMEMBER docunentation does not mention wildcard or special characters anywhere: inventing features which do not exist is unlikely to work.

[Devendra]

Thank you very much for your kind suggestions. Code is giving some error as follows

ans =

logical

1

T43RGN_20210119T053141_B03_10m.jp2

ans =

logical

1

T43RGN_20210119T053141_B04_10m.jp2

ans =

logical

0

Unable to perform assignment because the size of the left side is 5490-by-5490 and the size of the right side is

2745-by-2745.

It is also resampling already 20m resolution bands.

Please suggest me how to avoid 20m resolution bands and resample only 10m resolution bands.

Devendra

[Stephen23]

"Please suggest me how to avoid 20m resolution bands and resample only 10m resolution bands."

You use IF, just like you showed in your original question. Together with ENDSWITH, not with ISMEMBER.

For some reason you seem to be displaying the ENDSWITH output in the command window .... without using it for anything. I did not write that you should get rid of the IF, I wrote that you should replace ISMEMBER with ENDSWITH:

if endsWith(files(i+j).name, '_10m.jp2')
    img = imresize(img, 0.5, 'Method', 'bilinear');
end

In any case, rather than resizing images based on the filenames, you should probably resize the images based on the images sizes. That would likely be a much more reliable approach.

[Devendra]

I am very sorry for my mistake. It worked well. Thanks a lot for your kind help. However, when I am writing this layer stacked data into envi file using enviwrite, it is giving following error. If you could please suggest me how to use it properly, it will be great help to me. the part of code is as follows;

% Stack the image
stacked_image(:,:,j+1) = img;
end
fn = {files(i + j).name};
disp(string(fn));
end
disp(size(stacked_image));
img_names = regexp(fn,'\d+','match','once');
img_names = cellstr(reshape(img_names,1,[]));
fname = string(img_names(i)) + '_' + '6bands' + '.dat'
disp(fname);
enviwrite(stacked_image,fname);

it is giving following information

'C:\working_bpt\bands\'

T43RGN_20210119T053141_B03_10m.jp2

T43RGN_20210119T053141_B04_10m.jp2

T43RGN_20210119T053141_B05_20m.jp2

T43RGN_20210119T053141_B06_20m.jp2

T43RGN_20210119T053141_B07_20m.jp2

T43RGN_20210119T053141_B08_10m.jp2

5490 5490 6

fname =

"43_6bands.dat"

43_6bands.dat

Incorrect number or types of inputs or outputs for function enviwrite.

Error in ds_layer_stack (line 35)

enviwrite(stacked_image,fname);

Looking forward for your kind suggestions to write it in envi format.

Devendra

[Devendra]

As you have suggested

"In any case, rather than resizing images based on the filenames, you should probably resize the images based on the images sizes. That would likely be a much more reliable approach".

May I request you to please suggest me a starting point to resample based size rather than filenames?

I would appreciate your kind support and help.

Devendra

[Walter Roberson]

@Devendra

As discussed in https://www.mathworks.com/matlabcentral/answers/2109356-how-to-use-enviwrite-in-matlab enviwrite() expects a hypercube object. A version of enviwrite() that expects a cuboid of data is at https://github.com/akayasse/ENVI-read-and-write-for-MATLAB

[Devendra]

Thanks for your help. I have written envi file using enviwrite function. However, map information (latitude and longitude) with projection are missing. Please suggest me how to incorporate map information into envi header file. I will appreciate your kind help.

Devendra