Overlay data points on image plot and only rotate image points not the image using imref2d

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James
James 2024-11-20，20:15
评论： James about 16 hours 前
Ran in:
Hello,
I have the following data that I would like to overlay onto an image, and only flip the data points on the image and not the image itself.
load B.mat; %load reverse imcomplement of image
load x_world
load y_world
figure(1);
theta = -90; %rotate image counterclockwise
distorted = imrotate(B, theta);
ref = imref2d(size(distorted),[300 700], [100 550]); %set world coordinates
imshow(distorted,ref); %show image
set(gca, 'XTickLabel', flipud(get(gca,'XTickLabel') )); %change x-axis direction on image
hold on
plot(x_world,y_world,'r+','MarkerSize',12,'LineWidth',2); %overlay data points onto image
some code; %need to "flip/reflect" vertically only the data points. Not the image or x-axis.
I'm needing help on being able to flip/reflect vertically only the data points not the x-axis or the image.

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Matt J
Matt J 2024-11-20，20:36
编辑：Matt J 2024-11-20，20:37
Ran in:
load B.mat; %load reverse imcomplement of image
load x_world
load y_world
figure(1);
theta = -90; %rotate image counterclockwise
distorted = imrotate(B, theta);
ref = imref2d(size(distorted),[300 700], [100 550]); %set world coordinates
imshow(distorted,ref); %show image
set(gca, 'XTickLabel', flipud(get(gca,'XTickLabel') )); %change x-axis direction on image
hold on
y_world=sum(ref.YWorldLimits)-y_world;
plot(x_world,y_world,'r+','MarkerSize',12,'LineWidth',2);
hold off
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James
James about 19 hours 前
编辑：James about 16 hours 前
Hi this seems unstable. As sometime the red crosses flip accordingly like your example above and other times they don't flip at all. Any thoughts on that?

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更多回答（1 个）

Suraj Kumar
Suraj Kumar 2024-11-20，20:42
Hi James,
To overlay the data points on an image and flip them vertically (i.e. along Y-axis), you can refer to the following steps and the attached code snippets:
1. After plotting the image, you can determine the midpoint of the x-axis using the limits provided by the 'imref2d' object. This midpoint is used as the line of reflection.
% Calculate the midpoint of the x-axis range
x_min = ref.XWorldLimits(1);
x_max = ref.XWorldLimits(2);
x_mid = (x_min + x_max) / 2;
2. Compute the flipped x-coordinates by reflecting the original x-coordinates across the x-axis midpoint.
x_world_flipped = x_mid - (x_world - x_mid);
3. Plot the original data points in one color (e.g., red) and the flipped data points in another color (e.g., blue) on the same image.
% Plot the original data points
plot(x_world, y_world, 'r+', 'MarkerSize', 12, 'LineWidth', 2, 'DisplayName', 'Original Points');
% Plot the flipped data points
plot(x_world_flipped, y_world, 'b+', 'MarkerSize', 12, 'LineWidth', 2, 'DisplayName', 'Flipped Points');
You can go through the output below for a better understanding:
To learn more about the 'imref2d' function in MATLAB, please go through the following documentation:
https://www.mathworks.com/help/images/ref/imref2d.html
Hope this helps!
  1 个评论
James
James 2024-11-20，22:54
The issue now is that when you hover over the crosses, the values for the x coordinates do not match the placement on the x-axis.
Any ideas on how to flip the actual X coordinate values to match the position on the x-axis?

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