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Does `imshow` just delete all other objects in the axes?

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Albert Bing
Albert Bing on 21 Nov 2020
Edited: Mario Malic on 21 Nov 2020
It seems that imshow just deletes all other objects or handles in the parenting axes. Say I have a script like this
fig = figure;
ax = axes(fig);
text(ax, 0.5, 0.5, 'string');
h0 = findobj(ax, 'Type', 'text');
img = randn(128, 128);
imshow(img); % why is `imshow(ax, img)` illegal?
h = findobj(ax, 'Type', 'text');
h0 is a 1x1 text, but h is empty!
Another wierd behaviour of imshow is that you cannot set the axes in the imshow command, i.e. imshow(ax, img) is not allowed.
Why is imshow so different?


Albert Bing
Albert Bing on 21 Nov 2020
Sorry it was my carelessness. The point is the 'NextPlot' property of the axes. The default value is 'replace'. So to make the previous defined handles kept, it should be changed to 'add'.

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Accepted Answer

Mario Malic
Mario Malic on 21 Nov 2020
To use hold on with handles to axes, this works.
hold(ax, 'on');
To assign image to axes with imshow
imshow(img, 'Parent', ax)

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Albert Bing
Albert Bing on 21 Nov 2020
I checked my other code, turned out the axes was used as axes(fig, 'NextPlot', 'add').
So I guess imshow is not so different.

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