Problem with converted TIFF image

I converted a png to tiff unsigned int16. The image resulting is completely black.

This a apart of my code:

% Convert to unsigned 16-bit integer
img_uint16 = uint16(double(img) / double(intmax('uint16')) * 65535);
% Save the image as TIFF
tiffPath = fullfile(subfolderPath, [currentImage(1:end-4), '_converted.tif']);  
imwrite(img_uint16, tiffPath);

Answer 1

[Image Analyst]

Try

img_uint16 = uint16(double(img) / double(max(img(:))) * 65535);

or

img_uint16 = uint16(mat2gray(img) * intmax('uint16'));

[DGM]

Neither of these will preserve the image contrast, and the second is a disallowed mixed-class operation and will throw an error.

A = uint8([32 224]); % not a full-range image

% contrast is improperly skewed toward white for all values
B = uint16(double(A) / double(max(A(:))) * 65535) 

B = 1x2

9362 65535

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% even if you fixed the error, it would still change the contrast
C = uint16(mat2gray(A) * double(intmax('uint16')))

C = 1x2

0 65535

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% this is just an error
D = uint16(mat2gray(A) * intmax('uint16'))

Error using *
Integers can only be combined with integers of the same class, or scalar doubles.

While it's unlikely that the input class is signed integer, if it were, the first example would also cause gross data truncation, whereas the second would just cause the same contrast alteration.

Answer 2

[Walter Roberson]

Use im2uint16