python - 在图像上绘制曲线？

Question

假设我有一张带有一些黑色像素的图像。我知道黑色像素的所有坐标，我正在寻找黄线。

给定:我图像中黑色像素的坐标。

寻找:最适合黑色像素的黄色多项式

import cv2
import numpy as np

cv2.imread("foo.jpg")
#search for the black pixels and save the coordinates.

#coordinates of all pixels (example)
x = np.array([0.0, 1.0, 2.0, 3.0,  4.0,  5.0]) 
y = np.array([0.0, 0.8, 0.9, 0.1, -0.8, -1.0]) 
z = np.polyfit(x, y, 2)
p = np.poly1d(z)

如果我理解正确，现在我用 np.poly1d() 创建了一个多项式(图像上的黄线)。但是我怎样才能在我的 bgr_img 上绘制它呢？

编辑:

到目前为止，这是我的代码:

import cv2
import numpy as np

img = cv2.imread("white_foo.jpg") #1000x1000 pixel

#lets say these are my black pixels in a white image.
x = np.array([122, 224, 210, 350,  380,  250, 490, 623, 711, 819, 900])
y = np.array([536, 480, 390, 366, 270, 240, 180, 210, 280, 400, 501])

#calculate the coefficients.
z = np.polyfit(x, y, 2)
lspace = np.linspace(0, 1000, 100)

#here I want to draw the polynomial which I calculated with polyfit on my image

cv2.imshow("test", img)
cv2.waitKey(0)

提前致谢

Answer 1

Google 快速搜索:https://docs.opencv.org/2.4/modules/core/doc/drawing_functions.html#polylines

还有这个:Opencv polylines function in python throws exception

在任何情况下，您都需要在您感兴趣的点计算多项式，然后适本地格式化这些点(折线希望它们在 int32 容器中，格式如 [[x_1, y_1], [x_2 , y_2], ... , [x_n, y_n]]).然后调用函数即可。

draw_x = lspace
draw_y = np.polyval(z, draw_x)   # evaluate the polynomial

draw_points = (np.asarray([draw_x, draw_y]).T).astype(np.int32)   # needs to be int32 and transposed

cv2.polylines(img, [draw_points], False, (0,0,0))  # args: image, points, closed, color