在图形上绘制椭圆并获取坐标 [英] Draw an ellipse on a figure and get coordinates_Python
问题描述
我正在使用Python 2.7。我必须在图片上定义一些感兴趣的区域（AoI）。基本上，我想这样做是在图片的特定部分绘制一个椭圆（或更多），并获取其轮廓的坐标（x; y）。我想将这些坐标保存在文件中，以便以后使用它们以查看我的数据是否在此区域内。
I'm working on Python 2.7. I have to define some Areas of Interest (AoI) on a picture. Basically, I'm trying to do this drawing an ellipse (or more) on a specific part of the picture and to get the coordinates (x; y) of its contour. I want to save these coordinates on a file, in order to use them later to see whether (or not) my data are inside this area.
这是我的代码：
import matplotlib.pyplot as plt
import numpy as np
from matplotlib.patches import Ellipse, Circle
from matplotlib.path import Path
# Get an example image
img = imread('sposa.png')
# Create a figure. Equal aspect so circles look circular
fig,ax = plt.subplots(1)
ax.set_aspect('equal')
# Show the image
ax.imshow(img)
ax.set_xlim(0,1600)
ax.set_ylim(0,1200)
# Now, loop through coord arrays, and create a circle at each x,y pair
ellipse = Ellipse((1000, 400), width=400, height=100, edgecolor='white',facecolor='none',linewidth=2)
ax.add_patch(ellipse)
path = ellipse.get_path()
# Show the image
plt.show()
运行代码时，我得到了（这正是我想要的）：
When I run the code, I get this (that is exactly what I want):
但是，当我打印路径以进行检查时，我得到以下输出，（我想）与以下内容有关：
However, when I print the path in order to check it, I get the following output, which (I suppose) is exclusively related to the ellipse.
Path(array([[ 0. , -1. ],
[ 0.2652031 , -1. ],
[ 0.51957987, -0.89463369],
[ 0.70710678, -0.70710678],
[ 0.89463369, -0.51957987],
[ 1. , -0.2652031 ],
[ 1. , 0. ],
[ 1. , 0.2652031 ],
[ 0.89463369, 0.51957987],
[ 0.70710678, 0.70710678],
[ 0.51957987, 0.89463369],
[ 0.2652031 , 1. ],
[ 0. , 1. ],
[-0.2652031 , 1. ],
[-0.51957987, 0.89463369],
[-0.70710678, 0.70710678],
[-0.89463369, 0.51957987],
[-1. , 0.2652031 ],
[-1. , 0. ],
[-1. , -0.2652031 ],
[-0.89463369, -0.51957987],
[-0.70710678, -0.70710678],
[-0.51957987, -0.89463369],
[-0.2652031 , -1. ],
[ 0. , -1. ],
[ 0. , -1. ]]), array([ 1, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4,
4, 4, 4, 4, 4, 4, 4, 4, 79], dtype=uint8))
但是，我需要一个与图片像素（1600 X 1200）有关的椭圆坐标列表。我可能使用了错误的函数，或者图片和椭圆之间不匹配。
However, I need a list of coordinates of the ellipse in relation to the pixel of the picture (1600 X 1200). I'm probably using the wrong function or there is something that does not match between the picture and the ellipse.
我应该获得类似的内容（这是来自
I should obtain something like this (this is an example from a previous experiment):
[ Path(array([[ 1599. , 868.86791294],
[ 1598. , 868.87197971],
[ 1597. , 868.8801087 ],
...,
[ 1597. , 675.30378536],
[ 1598. , 675.31373204],
[ 1599. , 675.31870792]]), None)]
665
有人可以帮助我吗？
预先感谢您，
R
Can anyone help me? Thank you in advance, R
推荐答案
路径数组似乎是一个粗糙的归一化圆-我会忽略它
the path array appears to be a coarse normalized circle - I'd ignore it
您已经有了椭圆信息
ellipse = Ellipse（（1000，400），width = 400，height = 100，...）
我只是根据图中的第一个数字做一个sin的cos参数化椭圆 Ellipse（（1000，400），width = 400，height = 100 是要明确绘制高分辨率椭圆的中心点和轴长
I would just do a sin, cos paramaterized ellipse based on the 1st few numbers in Ellipse((1000, 400), width=400, height=100which are the center point and axis lengths if you want to draw a hi res ellipse explicitly
用于成员资格测试（x-x_0）^ 2 / a ^ 2 +（y-y_0）^ 2 / b ^ 2 <= 1 可能最好，其中 a ， b
是相应 width = 400，height = 100
for a membership test (x - x_0)^2/a^2 + (y - y_0)^2/b^2 <= 1 is probably best where a, b
are 1/2 of the respective width=400, height=100
当然，您只需要测试边界矩形内的像素索引
of course you would only need to test pixel indices within the bounding rectangle
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