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

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MathWorks Support Team 2010-7-29

0
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https://ww2.mathworks.cn/matlabcentral/answers/94170-how-can-i-reverse-the-y-axis-when-i-use-the-image-or-imagesc-function-to-display-an-image-in-matlab

编辑： madhan ravi 2019-2-3

I execute the following commands to display an image using the IMAGESC function:

load clown
clims = [10 60];
imagesc(X,clims)
colormap(gray)

The y-axis runs from the top of the image to the bottom. I would like to reverse the y-axis so that it starts at the bottom of the image and runs to to the top.

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Answer 1

MathWorks Support Team 2010-7-29

22
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https://ww2.mathworks.cn/matlabcentral/answers/94170-how-can-i-reverse-the-y-axis-when-i-use-the-image-or-imagesc-function-to-display-an-image-in-matlab#answer_103522

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This change has been incorporated into the documentation in Release 2009b (R2009b). For previous releases, read below for any additional information:

The first row of pixels is normally at the top of an image. By default, the IMAGE and IMAGESC functions invert the y-axis direction when the image is displayed on an axes by setting the 'YDir' property to 'reverse.' To invert the y-axis direction, set the 'YDir' property to 'normal', as follows:

load clown
clims = [10 60];
imagesc(flipud(X),clims)
colormap(gray)
set(gca,'YDir','normal')

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Royi Avital 2018-5-1

The problem is doing this flips the data as well. How could one only flip the axis yet not how the data is displayed?

Mary Abbott 2018-5-9

Hi Royi,

Only setting the 'YDir' property of the axes to 'normal' will flip how the y-axis is displayed, causing the image to appear upside down. To account for this, we use the "flipud" function to flip the image back. Essentially, we are flipping it horizontally twice, so the end result should not appear flipped.

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