Plot true color Sentinel-2A image

Through a combination of non-matlab/non-native tools (GDAL) as well as native tools (geoimread) I can ingest Sentinel-2A data either a indiviual bands or as an RGB image having employed gdal merge. I'm stuck at a point where using

imshow(I, [])

Produces a black image, with apparently no signal. The range of intensity values in the image are 271 - 4349. I know that there is a good signal in the image because when I do

bit_depth = 2^15;
I = swapbytes(I);
[I_indexed, color_map] = rgb2ind(I, bit_depth);
I_double = im2double(I_indexed, 'indexed');
ax1 = figure;
colormap(ax1, color_map);
image(I_double)

and index the image, collecting a colormap, I get a likeness of the region I'm exploring (albeit very strangely colored)

I'm currently considering whether I should try:

1. Find a low-level description of Sentinel-2A data, implement the scaling/correction
2. Use a toolbox, possibly this one.
3. Possibly adjust ouput settings in one of the earlier steps involving GDAL

Comments or suggestions are greatly appreciated.

[Matthew Cooper]

You might try pcolor or even something simple like contourf just to make sure the values are there (you would need to define x and y (lon and lat) vectors as well). You might also try geotiffread (if the data are saved as a .tif file) to ingest the data which would provide a MapCellsReference object which woudl allow you to use the in-built Matlab geospatial plotting functions, or if the data are not saved as geotiff go ahead and use geoimread and create a georeference object yourself and then try geoshow(I,R,'DisplayType','Surface') or one of the other display type options. Finally, if you post your Sentinel data file, I will have a look and figure it out for you.

[Iskander Benhadj]

dear,

to show the image using the imshow, you need to scale the image between 0 and 1

bit_depth = 2^15;
I = swapbytes(I);
[I_indexed, color_map] = rgb2ind(I, bit_depth);
I_double = im2double(I_indexed, 'indexed');
max_I = max(max(I_double));
min_I = min(min(I_double));
I_temp = (I_double - min_I)./(max_I - min_I);
imshow(I_temp);

Best,

Iskander