How to detect & fitting curvature from the binary image?

Question

DW 2023-11-21

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2050077-how-to-detect-fitting-curvature-from-the-binary-image

评论： Image Analyst 2023-11-23

采纳的回答： Mathieu NOE

I have a binary image, and I want to detect & draw curvature from the image.

This is my original image.

This is what I want.

Since the positions of arcs and straight lines in a binary image are not constant and thousands of images must be processed, I want to detect the pixel location without specifying it.

I did some searches, but not sure where should I start.

I would appreciate it if you could recommend some things to study.

Thank you.

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

Mathieu NOE 2023-11-21

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2050077-how-to-detect-fitting-curvature-from-the-binary-image#answer_1357192

在 MATLAB Online 中打开

hello

this would be my suggestion, based on this Fex submission :

smoothn - File Exchange - MATLAB Central (mathworks.com)

result

code :

filename = 'image.png';
tmp = imread(filename);
inpict = im2double(rgb2gray(tmp));
[m,n] = size(inpict);
% find values above threshold 
[y,x] = find(inpict>0.5);
% flip y direction (on the data)
y = m-y;
% take unique values 
[y,ia,ic] = unique(y);
x = x(ia);
% smooth the data with smoothn
% FEX : https://fr.mathworks.com/matlabcentral/fileexchange/25634-smoothn?s_tid=srchtitle
  z = smoothn({x,y},1e3,'robust');
  xs = z{1};
  ys = z{2};
subplot(1,2,1)
imshow(inpict);
subplot(1,2,2)
plot(x,y,'*k',xs,ys,'r');

2 个评论
显示无隐藏无

DW 2023-11-21

Thank you so much.

That was helpful.

Mathieu NOE 2023-11-21

as always , my pleasure !

请先登录，再进行评论。

Answer 2

Image Analyst 2023-11-21

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2050077-how-to-detect-fitting-curvature-from-the-binary-image#answer_1357327

See my solution to your duplicate question:

https://www.mathworks.com/matlabcentral/answers/2050272-curvature-detection-from-outlines-of-the-binary-image#answer_1357322

If you want, you could split the curve up into right half and left half but I assumed that the "thing" is actually some single surface with a rod sticking into it so both sides would probably have the same curvature so I just fit both sides to one polynomial.

2 个评论
显示无隐藏无

DW 2023-11-23

I tried "Mathieu NOE" 's solution also, but your solution helped me more with my specific problem.

Since the curved surfaces on the left and right are subtly (sometimes very) different, now I'm trying to fit the curves separately for the left and right.

Thank you again!

Image Analyst 2023-11-23

You could certainly split mine up into right and left sides. Note that @Mathieu NOE still had the spike in there, and it uses a File Exchange program, and smooths the data locally, while mine ignores the spike, uses only built-in functions, and fits the entire surface to a smooth polynomial rather than just smoothing locally. It just depends on how you prefer to do it.

请先登录，再进行评论。