Unable to display variable as image

I have the folowing variable

submat =

  7×13 single matrix

   16.1094   16.3903   12.4469   33.8613    6.7100   20.3669   27.7830   23.1273   10.9647   15.3839   43.2814   25.0800    4.9771
   26.0134   21.7846   24.5541   10.7064   24.3345    8.5626   38.1821   13.5120   12.4108   12.7480   14.2511   11.5835   10.3106
   21.8898   26.0016   24.3997   36.9177   14.0322   12.7298   11.1593   16.2164    8.3326    3.4838   23.6294   16.0808    8.5209
   21.7488   11.4966   17.9432   14.3220   13.1865   25.7872   53.9011    3.9896    3.8928    5.3149    9.3588    3.3960   12.8622
   23.8734   52.9111   25.0016   13.5389    9.8117   17.7362    3.2283   32.2506   25.0688   14.9008   15.3365    5.6434   12.1325
   34.5103   37.3330   13.4962   22.7538    6.1432   26.1014   14.8352    3.0524   10.7713    7.0607   13.4558   12.8980   11.2999
    8.4102   26.0903   13.1611   23.0215   21.3333   31.7792   19.9027   30.4275   15.3688   27.6668   17.8407   17.7286   19.2649

I want to display it as an image. The "figure" window opens, but it does not contain anything.

I have tried with imshow, image, imagesc, the result is always the same. What could be the problem?

Answer 1

[VBBV]

D = [16.1094   16.3903   12.4469   33.8613    6.7100   20.3669   27.7830   23.1273   10.9647   15.3839   43.2814   25.0800    4.9771
   26.0134   21.7846   24.5541   10.7064   24.3345    8.5626   38.1821   13.5120   12.4108   12.7480   14.2511   11.5835   10.3106
   21.8898   26.0016   24.3997   36.9177   14.0322   12.7298   11.1593   16.2164    8.3326    3.4838   23.6294   16.0808    8.5209
   21.7488   11.4966   17.9432   14.3220   13.1865   25.7872   53.9011    3.9896    3.8928    5.3149    9.3588    3.3960   12.8622
   23.8734   52.9111   25.0016   13.5389    9.8117   17.7362    3.2283   32.2506   25.0688   14.9008   15.3365    5.6434   12.1325
   34.5103   37.3330   13.4962   22.7538    6.1432   26.1014   14.8352    3.0524   10.7713    7.0607   13.4558   12.8980   11.2999
    8.4102   26.0903   13.1611   23.0215   21.3333   31.7792   19.9027   30.4275   15.3688   27.6668   17.8407   17.7286   19.2649]

D = 7×13

16.1094 16.3903 12.4469 33.8613 6.7100 20.3669 27.7830 23.1273 10.9647 15.3839 43.2814 25.0800 4.9771 26.0134 21.7846 24.5541 10.7064 24.3345 8.5626 38.1821 13.5120 12.4108 12.7480 14.2511 11.5835 10.3106 21.8898 26.0016 24.3997 36.9177 14.0322 12.7298 11.1593 16.2164 8.3326 3.4838 23.6294 16.0808 8.5209 21.7488 11.4966 17.9432 14.3220 13.1865 25.7872 53.9011 3.9896 3.8928 5.3149 9.3588 3.3960 12.8622 23.8734 52.9111 25.0016 13.5389 9.8117 17.7362 3.2283 32.2506 25.0688 14.9008 15.3365 5.6434 12.1325 34.5103 37.3330 13.4962 22.7538 6.1432 26.1014 14.8352 3.0524 10.7713 7.0607 13.4558 12.8980 11.2999 8.4102 26.0903 13.1611 23.0215 21.3333 31.7792 19.9027 30.4275 15.3688 27.6668 17.8407 17.7286 19.2649

imshow(D)  % this does not work 

imagesc(D) % this works

[VBBV]

May be you have tried with imshow

imshow takes only filenames as inputs

imshow('peppers.png')

[Alessandro Zuech]

Still does not work for me. I even tried declaring the variable like you did, but I still couldn't display it with imagesc.

[Image Analyst]

@VBBV "imshow takes only filenames as inputs" is not true. imshow takes image variables as inputs as well as filenames. Perhaps you were thinking of imread which takes only filenames.

Answer 2

[Image Analyst]

Because your submat is floating point, and not within the range 0 to 1, you'll need to use [] when you call imshow(). If you don't do that than any values more than 1 will be considered as being 1 (clipped to white) and any values less than 0 will be considered as 0 (clipped to black). Because all of your values were more than 1, the image showed up as all white.

Try this, using [] in imshow:

submat = [16.1094   16.3903   12.4469   33.8613    6.7100   20.3669   27.7830   23.1273   10.9647   15.3839   43.2814   25.0800    4.9771
    26.0134   21.7846   24.5541   10.7064   24.3345    8.5626   38.1821   13.5120   12.4108   12.7480   14.2511   11.5835   10.3106
    21.8898   26.0016   24.3997   36.9177   14.0322   12.7298   11.1593   16.2164    8.3326    3.4838   23.6294   16.0808    8.5209
    21.7488   11.4966   17.9432   14.3220   13.1865   25.7872   53.9011    3.9896    3.8928    5.3149    9.3588    3.3960   12.8622
    23.8734   52.9111   25.0016   13.5389    9.8117   17.7362    3.2283   32.2506   25.0688   14.9008   15.3365    5.6434   12.1325
    34.5103   37.3330   13.4962   22.7538    6.1432   26.1014   14.8352    3.0524   10.7713    7.0607   13.4558   12.8980   11.2999
    8.4102   26.0903   13.1611   23.0215   21.3333   31.7792   19.9027   30.4275   15.3688   27.6668   17.8407   17.7286   19.2649];
imshow(submat, [])  % This does work if you use [] to autoscale the data.

imagesc(submat) % this also works but applies some default colormap that you probably don't want.

If you use imshow(), you can then pseudocolor the image with a colormap with the colormap() function if you want, otherwise it shows up as grayscale.

Answer 3

[Alessandro Zuech]

I re-loaded MATLAB, and now I get this message:

MATLAB has experienced a low-level graphics error, and may not have drawn correctly.

Read about what you can do to prevent this issue at Resolving Low-Level Graphics Issues then restart MATLAB.

To share details of this issue with MathWorks technical support,

please include this file with your service request.

The solution of this problem is to start MATLAB differently. For me, it worked:

matlab -softwareopengl