How do I read multiband envi generated image file into matlab?

I am reading the multiband envi generated image file into matlab by using following matlab code;

img_path = 'C:\Image_Data\'

d = uigetdir(pwd, 'Select a folder');

imgfiles = dir(fullfile(d, '*.img'));

for m = 1:length(imgfiles)

img_file = imgfiles(m);

disp(img_file.name);

img = imread(img_file.name);

red = img(:,:,4); % red band

rededge1 = img(:,:,5); % rededge1 band

rededge2 = img(:,:,6); % rededge2 band

rededge3 = img(:,:,7); % rededge3 band

nir = img(:,:,8); % near infrared band

This is giving the following error

>> ds_indices_caf

img_path =

'C:\Image_Data\'

20240309_SAMPLE_DATA.img

Error using imread>get_full_filename

File "20240309_SAMPLE_DATA.img" does not exist.

Error in imread (line 372)

fullname = get_full_filename(filename);

Error in ds_indices_caf (line 17)

img = imread(img_file.name);

>>

I am attaching the envi image file and request to kindly help me out to read the data from the image file.

Deva

[Devendra]

I have kept matlab code and input data in same directory. Now following errors are coming;

>> ds_indices_caf

img_path = 'C:\Data\'

20240309_SAMPLE_DATA.img

Error using imread>get_format_info (line 554)

Unable to determine the file format.

Error in imread (line 395)

fmt_s = get_format_info(fullname);

Error in ds_indices_caf (line 17)

img = imread(img_file.name);

I would appreciate any help to fix it.

Deva

Answer 1

[Zuber Khan]

Hi,

As per my understanding, you are facing this issue because MATLAB's "imread" function might not support reading ".img" file format. This is also evident from the error message "Unable to determine the file format."

The "Hyperspectral Imaging Library for Image Processing Toolbox" Add-On allows us to work with ENVI files in MATLAB. Please refer to the following link to install an add-on in MATLAB:

https://www.mathworks.com/help/matlab/matlab_env/get-add-ons.html

The "hypercube" function provided by the add-on can be used to read the IMG and the HDR files. It creates a "hypercube" object which can be further analyzed using other hyperspectral-specific functions. The following documentation link provides more information on the same:

https://www.mathworks.com/help/images/ref/hypercube.html

However, the above function also requires the center wavelength values of each spectral band to be present in the metadata HDR file to read the IMG image data. In case the wavelength information is not available, the below commands can be used to read the files:

info = enviinfo('sample.hdr');
data = multibandread('sample.img', [info.Height info.Width info.Bands], info.DataType, ...
    info.HeaderOffset,info.Interleave,info.ByteOrder);

The returned "data" variable is a 2D matrix containing data corresponding to the input image data file. For more information on the functions used in the code above, please refer to the following documentation links:

• "enviinfo" - https://www.mathworks.com/help/images/ref/enviinfo.html
• "multibandread" - https://www.mathworks.com/help/matlab/ref/multibandread.html

I hope it helps resolve the issue.

Regards,

Zuber