Tutorial :How do I edit the axes of an image in MATLAB to reverse the direction?



Question:

I would like to edit the axes in my series of images being displayed.

This is what my image looks like:

parabola

As you can see, it ranges from 0 to about 500 from top to bottom. Can I invert that? Plus, I want to mirror the image being shown, so that it starts from left to right... or, if it's possible, to let the axes show from right to left.


Solution:1

To reverse an axis, you can set the 'XDir' or 'YDir' property of the current axes to 'reverse':

set(gca,'XDir','reverse');  %# This flips the x axis  

Keep in mind that flipping an axis in this way flips everything in the plot as well. This probably isn't what you want to do for the y axis. You probably just want to flip the y axis labels, which you can do by modifying the 'YTickLabel' property in the following way:

yLimits = get(gca,'YLim');  %# Get the y axis limits  yTicks = yLimits(2)-get(gca,'YTick');  %# Get the y axis tick values and                                         %#   subtract them from the upper limit  set(gca,'YTickLabel',num2str(yTicks.'));  %'# Convert the tick values to strings                                             %#   and update the y axis labels  


Solution:2

Im = imread('onion.png');    Im = flipdim(Im ,1); % vertical flip the image.    axis xy; %set the xy to be at (0,0), this flips the image back again.  

And whoop dee doo the image now have an y axis with the range from bottom to top!

How can I reverse the y-axis when I use the IMAGE or IMAGESC function to display an image in MATLAB? Another solution from mathworks


Solution:3

I found gnovice's answer helpful but it needed some tweaks for me. I think the following is a more general way to reverse the labels on the y axis. Simply sort the y tick numbers in descending order and relabel.

yTicks = get(gca,'YTick');     yTicks_reverse = sort(yTicks,2,'descend');                                        set(gca,'YTickLabel',num2str(yTicks_reverse.'));   


Solution:4

I was redirected here from a duplicate question: Flipping axis ticks

What 'ale' wanted to do there was just to flip the y-axis direction to be top down. If that is the only thing needed and nothing else, I would use:

axis ij  

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