# How to rotate imellipse

10 visualizzazioni (ultimi 30 giorni)
erik il 23 Mag 2013
Risposto: Tim Jackman il 25 Set 2018
Hello fellow Matlab users,
I'm currently using the imellipse function to draw an ellipse on an image. I would like to rotate the ellipse interactively. However I cannot get this to work. Does anyone have experience with rotating ellipses? Please share, it would help me out a lot!
With kind regards,
Erik Groot Jebbink
##### 0 CommentiMostra -2 commenti meno recentiNascondi -2 commenti meno recenti

Accedi per commentare.

### Risposta accettata

Image Analyst il 23 Mag 2013
See my demo. It doesn't use imellipse() so you can't have handles to click and drag out new a size or angle. So you'd need to have a GUI with some sliders to allow the user to set new parameters for the major axis length, minor axis length, center location, and angle or orientation.
clc; % Clear the command window.
workspace; % Make sure the workspace panel is showing.
format longg;
format compact;
fontSize = 20;
% Parameterize the equation.
t = linspace(0, 360,1000);
phaseShift = 20;
xAmplitude = 2;
yAmplitude = 1;
x = xAmplitude * sind(t + phaseShift);
y = yAmplitude * cosd(t);
% Now plot the rotated ellipse.
plot(x, y, 'b-', 'LineWidth', 2);
axis equal
grid on;
xlabel('X', 'FontSize', fontSize);
ylabel('Y', 'FontSize', fontSize);
title('Rotated Ellipses', 'FontSize', fontSize);
text(-1.75, 1.4, 'Parametric --', 'Color', 'b', 'FontSize', fontSize);
% Now plot another ellipse and multiply it by a rotation matrix.
% http://www.maa.org/joma/Volume8/Kalman/General.html
rotationAngle = 30;
transformMatrix = [cosd(rotationAngle), sind(rotationAngle);...
-sind(rotationAngle), cosd(rotationAngle)]
xAligned = xAmplitude * sind(t);
yAligned = yAmplitude * cosd(t);
xyAligned = [xAligned; yAligned]';
xyRotated = xyAligned * transformMatrix;
xRotated = xyRotated(:, 1);
yRotated = xyRotated(:, 2);
hold on;
plot(xRotated, yRotated, 'g-', 'LineWidth', 2);
% Plot a line at 30 degrees
slope = tand(30);
x1 = min(x(:));
y1 = slope * x1;
x2 = max(x(:));
y2 = slope * x2;
line([x1 x2], [y1 y2], 'Color', 'r');
text(-1.75, 1.25, 'Rotation Matrix --', 'Color', 'g', 'FontSize', fontSize);
text(-1.75, 1.1, '30 Degree Line --', 'Color', 'r', 'FontSize', fontSize);
% Enlarge figure to full screen.
set(gcf, 'units','normalized','outerposition',[0 0 1 1]);
##### 0 CommentiMostra -2 commenti meno recentiNascondi -2 commenti meno recenti

Accedi per commentare.

### Più risposte (3)

Tim Jackman il 25 Set 2018
Beginning in R2018b, you can create an interactive ellipse ROI using the drawellipse function. This new ROI supports interactive rotation.
##### 0 CommentiMostra -2 commenti meno recentiNascondi -2 commenti meno recenti

Accedi per commentare.

Matt J il 23 Mag 2013
I believe imellipse objects are 4 DOF only :-(
##### 0 CommentiMostra -2 commenti meno recentiNascondi -2 commenti meno recenti

Accedi per commentare.

erik il 27 Mag 2013
Image Analyst, thank you for your contribution. I created a small gui with some sliders to move the ellipse around.
##### 3 CommentiMostra 1 commento meno recenteNascondi 1 commento meno recente
Image Analyst il 27 Ott 2013
as hz, I already pretty much gave code. All you need to do is to put it into a function called DrawEllipse which you call from the sliders. In the slider callbacks you set rotationAngle or some x and y offset/shift/translation, then call DrawEllipse passing those in.
YUKAi LIU il 10 Mag 2018
Modificato: Matt J il 10 Mag 2018

Accedi per commentare.

### Categorie

Scopri di più su Live Scripts and Functions in Help Center e File Exchange

### Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by