Save an imagesc output in Matlab

Question

I am using imagesc to get an integral image. However, I only manage to display it and then I have to save it by hand, I can't find a way to save the image from the script with imwrite or imsave. Is it possible at all?

The code:

image='C:\image.jpg';
in1= imread((image));
in=rgb2gray(in1);
in_in= cumsum(cumsum(double(in)), 2);
figure, imagesc(in_in);

@George what do you mean empty? 0 bytes file? All white? All black? — carandraug, Aug 27 '12 at 17:22

score 6 · Accepted Answer · edited Aug 28 '12 at 02:28

6

You can also use the print command. For instance if you are running over multiple images and want to serialize them and save them, you can do something like:

% Create a new figure
figure (fig_ct)
% Plot your figure

% save the figure to your working directory
eval(['print -djpeg99 '  num2str(fig_ct)]);
% increment the counter for the next figure
fig_ct = fig_ct+1;

where fig_ct is just a counter. If you are interested in saving it in another format different than jpeg take a look at the documentation, you can do tiff, eps, and many more.

Hope this helps

edited Aug 28 '12 at 02:28

tmpearce

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answered Aug 27 '12 at 18:01

Malife

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The function syntax (`print(gcf, '-djpeg99', num2str(fig_ct))`) should (nearly) always be preferred to using `eval` – tmpearce Aug 28 '12 at 02:27
Thanks! Will look into changing my scripts to the preferred usage. – Malife Aug 28 '12 at 13:40

score 4 · Answer 2 · edited Mar 30 '14 at 11:49

I believe your problem may be with the fact that you are saving a double matrix that is not on the range of [0 1]. If you read the documentation, you'll see that

If the input array is of class double, and the image is a grayscale or RGB color image, imwrite assumes the dynamic range is [0,1] and automatically scales the data by 255 before writing it to the file as 8-bit values.

You can convert it yourself to a supported type (that's logical, uint8, uint16, or double) or get it in the range [0 1] by, for example, dividing it by the max:

imwrite (in_in / max (in_in(:)), 'out.jpg');

You may still want to further increase the dynamic range of the image you saved. For example, subtract the mininum before dividing by the max.

in_in = in_in - min (in_in(:));
in_in = in_in / max (in_in(:));
imwrite (in_in, 'out.jpg');

If you want exactly what imagesc displays

The imagesc function scales image data to the full range of the current colormap.

I don't know what exactly does it mean exactly but call imagesc requesting with 1 variable, and inspect the image handle to see the colormap and pass it to imwrite().

Thank you for the solution and most of all for the explanation! :) — George, Aug 27 '12 at 17:56

score 1 · Answer 3 · edited Jan 22 '14 at 01:53

1

I'm a very new programmer, so apologies in advance if this isn't very helpful, but I just had the same problem and managed to figure it out. I used uint8 to convert it like this:

imwrite(uint8(in_in), 'in_in.jpg', 'jpg');

edited Jan 22 '14 at 01:53

Josh Crozier

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answered Jan 22 '14 at 01:33

Serena

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Save an imagesc output in Matlab

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