How can I save my scalogram image?

I am creating a scalogram with:

img=cwt(signal);

I want to save the scalogram produced. I am looking just to save the image itself; no axes, title, key, etc.

I am trying:

exportgraphics(img,"cwt.png")

and receive errror:

Error using exportgraphics

First parameter must specify the axes or chart object.

Is img not the object I want since that is where I saved the cwt(signal)?

Answer 1

[Rik]

Since it clears the current figure (and then creates the object, the easiest way is to this:

img=cwt(signal);
exportgraphics(gca,"cwt.png");

[Reid Demass]

Thank you, I was able to save the image. As a follow-up, is there a way to have only the scalogram saved? For example, I was able to save the image attached test2. However, I am only looking to retain what is in test3, which I manually cropped.

I have looked through example https://www.mathworks.com/help/deeplearning/ug/classify-time-series-using-wavelet-analysis-and-deep-learning.html?s_eid=PSM_25538&cid=%3Fs_eid%3DPSM_25538%26%01Classify+ECG+Signals+Using+Wavelet+Analysis+and+Deep+Learning in which scalograms are saved using a helper function, but it is not clear to me in the function code how they are removing the unwanted components of the image.

[Rik]

load mtlb
cwt(mtlb,Fs)

h=get(gca,'Children');
h_im=findobj(h,'Type','Image');
figure,imshow(h_im.CData)

So, as you can see, you will have to rescale based on the XData and YData properties to view it properly. Then you will have to apply a colormap to convert it to a color image. (but this way you have the actual data instead of a screenshot)