How to reverse Y axis on image?

Question

Elisa Lafforgue 2018-6-29

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/408041-how-to-reverse-y-axis-on-image

评论： Lana Neoricic 2021-1-7

Hello,

First of all, I know this question is dumb and that there is plenty of thread on it, but I could not find any solution in those. I already tried a lot of things and it did not work for me. Thus I came here for assistance.

I use the code below to show an image of a flame. In order to mesure the flame length, I have to plot axis. I managed to have axis and all, with a custom origin point, but I could not reverse the y axis.

figure(7);clf;
Image = 'input.jpg';
[rows, columns, ColorChannels] = size(Image);
origin = [center] % center is a well defined coordinates
xdata = -origin(1): columns - origin(1);
ydata = -origin(2): columns - origin(2);
imshow(Image, 'XData', xdata, 'YData', ydata);
axis on;
grid on;

I already tryed a lot of different solutions I found here and it seems some of them have no effect at all So for:

set(gca,'YDir','reverse')
set(gca,'YDir','normal')
set(gcf,'YDir','reverse')
axis ij
set(hAxes,'YDir','reverse')

Some inversed the whole image (I just want the y axis reversed), such as

fliplr or flipud (ydata) in the imshow

I suppose it might be the "imshow" doing but my image is not from a folder but from a previous matlab code (my figure show the image created just before this part of the code in matlab and this image is not saved anywhere in my folders) so I don't know if there is another solution than imshow for this case.

Do I use the code to reverse axis right? Is there any other solutions?

Ps: I tried to put those codes above in different location (before and after the "imshow") yet it still has no effect at all

3 个评论
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Dogukan Engin 2019-1-7

Hello,

I also need help on this one.

Thanks,

Rik 2019-1-7

Since there is an accepted answer: did you try it, and if so, how didn't it work?

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Answer 1

Sergey Efremov 2018-8-29

5
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/408041-how-to-reverse-y-axis-on-image#answer_334480

By default, y axis of an image is upside-down, values ascending from top down. If you set(gca,'YDir','normal'), you will reverse y axis. (gca,'YDir','reverse') will only leave y axis unchanged from default.