How to improve the filtering of a bubble image

Question

Jórdan Venâncio Leite 2020-4-14

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/517680-how-to-improve-the-filtering-of-a-bubble-image

评论： Rena Berman 2020-10-12

I need to better filter my image (a bubble) in order to obtain a better filtering than the one I already have (code), in order to get a better approximation of the contour of the bubble.

Would you know of any other filters or what I could change in my code to improve the borders I drew in red and to make the filtered image of the bubble (image 2) better look like the real bubble outline? (it should look like a semi-ellipse)

Thanks in advance

clc
clear
close all
% 1 - Reading the image
image = imread('bubble.png');
figure, imshow(image);
% 2 - Cropping the image
cropped = imcrop(image,[552.9 0 639.2 1080]);
figure, imshow(cropped);
% 3 - Gray scale
gray = rgb2gray(cropped);
figure, imshow(gray);
% 4 - Threshold filter
thresh = im2bw(gray, 0.5);
figure, imshow(thresh);
% 5 - Small pixel cluster removal filter
remove = bwareaopen(thresh, 13200);
figure, imshow(remove);
% 6 - Close connections filter
se = strel('line',300,0);
closing = imclose(remove,se);
figure, imshow(closing);
% 7 - Fill center of objects filter
OriginalLine = closing(1 , :);
OriginalLine2 = closing(end , :);
closing(1, :) = true; 
closing(end, :) = true;
fill = imfill(closing, 'holes');
closing(end,:) = false;
closing(1,:) = false;
fill(1, :) = OriginalLine;
fill(end, :) = OriginalLine2;
figure, imshow(fill);

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Rik 2020-6-11

(Retrieved from Google cache)

Question title:

How to improve the filtering of a bubble image

Question body:

I need to better filter my image (a bubble) in order to obtain a better filtering than the one I already have (code), in order to get a better approximation of the contour of the bubble.

Would you know of any other filters or what I could change in my code to improve the borders I drew in red and to make the filtered image of the bubble (image 2) better look like the real bubble outline? (it should look like a semi-ellipse)

Thanks in advance

clc
clear
close all
% 1 - Reading the image
image = imread('bubble.png');
figure, imshow(image);
% 2 - Cropping the image
cropped = imcrop(image,[552.9 0 639.2 1080]);
figure, imshow(cropped);
% 3 - Gray scale
gray = rgb2gray(cropped);
figure, imshow(gray);
% 4 - Threshold filter
thresh = im2bw(gray, 0.5);
figure, imshow(thresh);
% 5 - Small pixel cluster removal filter
remove = bwareaopen(thresh, 13200);
figure, imshow(remove);
% 6 - Close connections filter
se = strel('line',300,0);
closing = imclose(remove,se);
figure, imshow(closing);
% 7 - Fill center of objects filter
OriginalLine = closing(1 , :);
OriginalLine2 = closing(end , :);
closing(1, :) = true; 
closing(end, :) = true;
fill = imfill(closing, 'holes');
closing(end,:) = false;
closing(1,:) = false;
fill(1, :) = OriginalLine;
fill(end, :) = OriginalLine2;
figure, imshow(fill);

Rena Berman 2020-10-12

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Answer 1

Image Analyst 2020-4-17

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/517680-how-to-improve-the-filtering-of-a-bubble-image#answer_426524

activecontour_demo.m

Can you assume the ellipse axes will be vertical and horizontal? If not, see the FAQ: Click here

Otherwise you can use bwferet() to get the caliper dimension in one direction. Call it 2*a. Use sum() or regionprops() to get the area and centroid,

binaryImage = bwareafilt(binaryImage, 1); % Take largest blob only.
props = regionprops(binaryImage, 'Area', 'Centroid');
area = props.Area;
xCenter = props.Centroid(1);
yCenter = props.Centroid(2);
hold on;
plot(xCenter, yCenter, 'r+', 'MarkerSize', 60, 'LineWidth', 2); % Plot crosshairs at the centroid.

then, since the area of an ellipse is pi*a*b,

b = area / (pi * a);

Create an ellipse from the code in the FAQ:

xCenter = 12.5;
yCenter = 10;
xRadius = 2.5;
yRadius = 8;
theta = 0 : 0.01 : 2*pi;
x = xRadius * cos(theta) + xCenter;
y = yRadius * sin(theta) + yCenter;
plot(x, y, 'LineWidth', 3);
grid on;

where xRadius = b and yRadius = a (if vertical is the feret diameter direction you picked).

Or you might try activecontour(). See attached demo.

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Image Analyst 2020-4-18

You have an old version then. Try using regionprops() and getting the MajorAxisLength and MinorAxisLength, which are the axes of an ellipse fit to your blob.