How to use custom enviwrite code to use map_info for generating envi header file?

I want to use custom_enviwrite matlab code(attached) to use the map_info (attached) generated from sentinel2 image of jp2 format to produce the envi header file similar to attached header file. I request larger matlab community to suggest me how to achive this. I will appreciate your kind cooperation and help.

Devendra

Answer 1

[Suraj Kumar]

Hi Devendra,

Based on my understanding, you want to generate an ENVI header file using MATLAB function ‘custom_ enviwrite’. To achieve this, you can go through the following steps and the attached code snippets:

1. Extract and format the 'map_info' and 'projection_info' strings from the data to match the ENVI header requirements.

% Construct the coordinate_information struct 
map_info = 'UTM, 1.000, 1.000, 699960.000, 3300000.000, 20.000000, 20.000000, 43, North, WGS-84, units=Meters'; 
projection_info = 'PROJCS["WGS_1984_UTM_Zone_43N",GEOGCS["GCS_WGS_1984",DATUM["D_WGS_1984",SPHEROID["WGS_1984",6378137.0,298.257223563]],PRIMEM["Greenwich",0.0],UNIT["Degree",0.0174532925199433]],PROJECTION["Transverse_Mercator"],PARAMETER["False_Easting",500000.0],PARAMETER["False_Northing",0.0],PARAMETER["Central_Meridian",75.0],PARAMETER["Scale_Factor",0.9996],PARAMETER["Latitude_Of_Origin",0.0],UNIT["Meter",1.0]]'; 

2. Organize the data by creating structures for coordinate and wavelength data.

% Coordinate information structure 
coordinate_information.map_info = map_info_str; 
coordinate_information.projection_info = projection_info_str; 
% Wavelength data 
wavelength_data = [560.0, 665.0, 705.0, 740.0, 783.0, 842.0, 865.0]; 

3. Implement the ‘custom_enviwrite’ function validating the inputs to match the expected formats and convert images to suitable formats if necessary. Then write the image to a binary file and create a ENVI header file.

 function custom_enviwrite(image, fname, coordinate_information, wavelength_data) 
       img = single(image);   
       cl = class(img); 
       data_types = [4, 1, 2, 3, 12, 13]; 
       t = data_types(strcmp({'single', 'int8', 'int16', 'int32', 'uint16', 'uint32'}, cl)); 
       wfid = fopen(fname, 'w'); 
       fwrite(wfid, img, cl); 
       fclose(wfid); 
       fid = fopen([fname '.hdr'], 'w'); 
       fprintf(fid, 'ENVI\n'); 
       fprintf(fid, 'description = {Exported from MATLAB}\n'); 
       fprintf(fid, 'samples = %i\n', size(image, 2)); 
       fprintf(fid, 'lines = %i\n', size(image, 1)); 
       fprintf(fid, 'bands = %i\n', size(image, 3)); 
       fprintf(fid, 'data type = %i\n', t); 
       fprintf(fid, 'interleave = bsq\n'); 
       fprintf(fid, 'map info = {%s}\n',    coordinate_information.map_info); 
       fprintf(fid, 'projection info = {%s}\n',    coordinate_information.projection_info); 
       fprintf(fid, 'wavelength units = Nanometers\n'); 
       fprintf(fid, 'wavelength = {\n%.2f',  wavelength_data(1)); 
       for j = 2:length(wavelength_data) 
           fprintf(fid, ', %.2f', wavelength_data(j)); 
       end 
       fprintf(fid, '}\n'); 
       fclose(fid); 
   end 

4. Generate the ENVI files by executing the function to create the files.

fname = 'output_image';  
custom_enviwrite(image_data, fname, coordinate_information, wavelength_data); 

To know more about the ‘strcmp’ or ’class’ functions in MATLAB, you can refer the following documentations:

• https://www.mathworks.com/help/matlab/ref/strcmp.html
• https://www.mathworks.com/help/matlab/ref/class.html

Hope this helps!