Draw a curve line through drops in OpenCV C ++

Question

I am trying to draw a line that goes through these drops. Below is an example of an example.

I want the curve line to go through several blocks in the horizontal direction, as shown below.

Answer 1

As an example:

import cv2 import numpy as np img = cv2.imread('image.jpg') gray = cv2.cvtColor(img, cv2.COLOR_RGB2GRAY) (_, contours, _) = cv2.findContours(gray, cv2.RETR_LIST, cv2.CHAIN_APPROX_SIMPLE) # biggest area target = max(contours, key=lambda x: cv2.contourArea(x)) cv2.drawContours(img, [target], -1, [0, 0, 255], -1) # debug # just example of fitting x = target[:, :, 0].flatten() y = target[:, :, 1].flatten() poly = np.poly1d(np.polyfit(x, y, 5)) for _x in range(min(x), max(x), 5): # too lazy for line/curve :) cv2.circle(img, (_x, int(poly(_x))), 3, [0, 255, 0]) cv2.imshow('result', img) cv2.waitKey(0) 

Answer 2

Just for fun, and using the Perl TMTOWTDI philosophy (“There's more than one way to do this”), I extracted all the white points of your outlines into a file called points.dat and submitted it to gnuplot to fit the curve that gave me the formula for best line of compliance:

 y=3.10869110524588e-07*x*x*x -0.000972406154863963*x*x + 0.861790477479291*x + 307.220397010312 

And then I painted this in red on your source paths using awk and ImageMagick .

 #!/bin/bash convert contours.jpg -colorspace gray -threshold 50% txt: | awk -F: '/white/{print $1}' | tr ',' ' ' > points.dat { echo 'f(x) = a*x**3 + b*x**2 + c*x + d'; \ echo 'fit f(x) "points.dat" via a, b, c, d'; \ echo 'print a,"*u^3 + ",b,"*u^2 + ",c,"*u + ",d'; \ } | gnuplot 2>&1 | tail -1 awk 'BEGIN{ for(x=0;x<1504;x++){ y=3.10869110524588e-07*x*x*x -0.000972406154863963*x*x + 0.861790477479291*x + 307.220397010312 y=int(y) print "point ",x,y } }' /dev/null > p.mvg convert contours.jpg -draw @p.mvg z.png 

The beginning of points.dat as follows:

 769 453 770 453 771 453 772 453 773 453 769 454 765 455 766 455 767 455 768 455 ... ... 

The beginning of p.mvg as follows:

 fill red point 0 307 point 1 308 point 2 308 point 3 309 point 4 310 point 5 311 point 6 312 point 7 313 point 8 314 ... ...