why the coordinates start from 800. want it to start from 0 . and the origin point in the left down like usual.

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Mustafa Alhandhali 2019-3-11

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评论： Mustafa Alhandhali 2019-3-24

采纳的回答： Adam Danz

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this the code i use

%load the image called test1 
rgbImage = imread('test1.JPG');
% Get the dimensions of the image.  numberOfColorBands should be = 3.
[rows, columns, numberOfColorBands] = size(rgbImage);
% Display the original color image.
subplot(2, 2, 1);
imshow(rgbImage);
axis on; grid on
title('Original Color Image');

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Adam Danz 2019-3-11

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The funtion imshow() flips the y axis. To make the y-axis normal again.

ax = gca;
ax.YDir = 'normal'; 

However, your image will also flip its y direction.

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dpb 2019-3-12

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Yes, I know what he wants...but sometimes we can't always have what we want and this is one of those times.

As said, you could fake it by simply writing the tick labels as the reverse or

hAx=gca;
ytk=hAx.YTick;
hAx.YTickLabel=max(ytk)-ytk;

Mustafa Alhandhali 2019-3-24

thank you it works now

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dpb 2019-3-11

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编辑：dpb 2019-3-11

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imshow by default uses size() of the image x- and y- dimensions +/-0.5 as the axis x- and y-limits. The data are plotted on the axes from 1:Nx and 1:Ny so If you actually make the limits to be 0, you'll have a little background area outside the actual image data.

And, it always shows images with origin at top left. You can flip the axes, but unless you also flip() the image data in the y-direction, the image will be displayed upside down.

imshow(flipud(rgbImage))      % show the image in reversed y-direction
hAx=gca;                        % the parent axes handle
hAx.YDir='normal';              % invert the axis to go from bottom up so is displayed right side up