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Azzera filtri

Conversion of (129x7 complex double) to an Image

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I have a variable s (129x7 complex double). I want to save it as an image. I have tried many ways but I can't save it.
for k=1:size(cm,2)
s = spectrogram(cm(:,k));
save(['Spectro_Subj' num2str(h) '_channel' num2str(i) '_window' num2str(k) '.mat'],'s')
  2 Commenti
DGM il 4 Feb 2023
Typical image formats (BMP,PNG,JPG) support unsigned integer (or logical) datatypes. Some (TIFF) can be wrangled into supporting floating-point numeric data, but you shouldn't expect anything to be able to read the file. No image format that I know of supports complex-valued numeric data. You may be able to store the components of the data in separate images (real and imag), or perhaps it may suffice to reduce it to magnitude only.
Long story short, if you have arbitrarily-scaled complex data and you want to save it as a typical image format, you'll have to decide on a means of preserving scale information, and you'll have to decide which components of the complex data you want to keep or how you want to encode them into a single real-valued integer array (perhaps magnitude/phase can be encoded as intensity/hue?).
Walter Roberson
Walter Roberson il 4 Feb 2023
Tiff supports ComplexIEEEFP. However MATLAB's interface to libTiff does not support that.

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Image Analyst
Image Analyst il 6 Feb 2023
Modificato: Image Analyst il 7 Feb 2023
for k=1:size(cm,2)
baseFileName = sprintf('Spectro_Subject %d_channel %d_window %d.png', h, i, k);
fullFileName = fullfile(pwd, baseFileName);
fprintf('For k = %d, saving "%s".\n', k, fullFileName);
exportgraphics(gca, fullFileName);
  8 Commenti
Muhammad il 7 Feb 2023
@Image Analyst thank you so much i will. In the mean time as you can see i segment the signal into 3.5s frame windows, i need to have time (0-3.5s) on x axis and Frequency on Y axis. Currently i am just getting samples and normalized frequency. please have a look into the below attachement.
DGM il 7 Feb 2023
Note the only reason why I don't use exportgraphics() isn't because saveas() is better. I just run an older version, so I can't verify my example with something I can't run.

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Più risposte (2)

Walter Roberson
Walter Roberson il 4 Feb 2023
you could use the tiff gateway and write the imaginary component as unassociated alpha. There is an example at
The difference is that you would specify 2 samples per pixel instead of 4, and you would use IEEEFP sample format.
There is a file exchange contribution for writing floating-point tiff that is worth studying.
So... you would be able to use an image file, and use floating point samples, and write two channels.
What you should not expect is for any other program to be able to produce a readable image from the data

DGM il 4 Feb 2023
Spostato: Image Analyst il 6 Feb 2023
Are you sure you don't want to just save a graphical representation (i.e. a plot)?
% some fake test signal
fs = 1000;
t = 0:1/fs:2-1/fs;
y = chirp(t,100,1,200,'quadratic');
% plot the spectrogram
% save the figure
If so, there are many different ways it can be represented.

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