set elliptical ROI to zero in an image

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Mohamed Amine Henchir 2018-8-16

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/415165-set-elliptical-roi-to-zero-in-an-image

评论： Image Analyst 2018-8-27

I'm using an algorithm to detect ellipses in an image, it returns the center major minor axis and the orientation, but I would like to delete the detected ones to avoid double detection. I believe the way to do it is to create a mask with an elliptical ROI set it to zero and then subtract it from the original image... anyone knows what function to use? tired to use imellipse but I couldn't figure out a way to get it to work with the detection algorithm.

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采纳的回答

Image Analyst 2018-8-16

0
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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/415165-set-elliptical-roi-to-zero-in-an-image#answer_333050

编辑：Image Analyst 2018-8-16

在 MATLAB Online 中打开

mask_multiple_ellipses.m

To erase your image where you have an elliptical mask, do

grayImage(mask) = 0;

See attached demo.

If you need more help, you'll have to post your existing code.

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Mohamed Amine Henchir 2018-8-27

在 MATLAB Online 中打开

here is what I have, for now, I'm using the coordinates of a random ellipse and using poly2mask to create the mask and then subtracting it from the original image

if true
  A = imread('one.jpg');
figure;
imshow(A);
hold on;
% Parameterize the equation.
t = linspace(0, 360,1000);
phaseShift = 0;
xAmplitude = 2;
yAmplitude = 1;
x = xAmplitude * sind(t + phaseShift);
y = yAmplitude * cosd(t);
mask = poly2mask(x, y, 256, 256);
A(mask)= 0;
imshow(A);
end
but nothing is happening!

Image Analyst 2018-8-27

在 MATLAB Online 中打开

Your x and y only went from 0-1 - less than a pixel! And your ellipse didn't have a center specified. Try this:

grayImage = imread('cameraman.tif');
subplot(2, 2, 1);
imshow(grayImage);
[rows, columns, numberOfColorChannels] = size(grayImage);
hold on;
% Parameterize the equation.
t = linspace(0, 360, 1000);
phaseShift = 0;
xAmplitude = columns/3;
yAmplitude = rows/5;
xCenter = columns/2;
yCenter = rows/2;
x = xAmplitude * sind(t + phaseShift) + xCenter;
y = yAmplitude * cosd(t) + yCenter;
mask = poly2mask(x, y, rows, columns);
subplot(2, 2, 2);
imshow(mask);
grayImage(mask)= 0;
subplot(2, 2, 3);
imshow(grayImage);