I am trying to put together a simple code without any python libraries.

the aim is to find the centerline of a rectangle (for the longest side specifically).

This is my code so far. (it is looking for the center coordinates).

I want to be able to fine the centerline nonmatter the orientation of the rectangle. how do you recommend I do it. I’m open to any advice.

import matplotlib.pyplot as plt

x = [4,4,-4,-4]

y = [8,-5,-5,8]


x1,y1 = x[0],y[0]
x2,y2 = x[1],y[1]
x3,y3 = x[2],y[2]
x4,y4 = x[3],y[3]

ch_y1 = y1-y2
ch_y2 = y1-y4
ch_x1 = x1-x2
ch_x2 = x1-x4

l1 = ((x1-x2)**2+(y1-y2)**2)**0.5
l4 = ((x1-x4)**2+(y1-y4)**2)**0.5
l2 = ((x2-x3)**2+(y2-y3)**2)**0.5
l3 = ((x3-x4)**2+(y3-y4)**2)**0.5

if l2 > l1:
    if abs(1-l1/l3) < 0.3 :
        if x1>x2:
            x11 = x1 - l2/2
            
        if x1<x2:
            x11 = x1 + l2/2
            
        if x1 == x2:
            x11 = x1 
            
        if y1>y2:
            y11 = y1 - l2/2
            
        if y1<y2:
            y11 = y1 + l2/2
            
        if y1 == y2:
            y11 = y1 
            
            
        if x2>x3:
            x12 = x2 - l3/2
            
        if x2<x3:
            x12 = x2 + l3/2
            
        if x2 == x3:
            x12 = x2 
            
        if y2>y3:
            y12 = y2 - l3/2
            
        if y2<y3:
            y12 = y2 + l3/2
            
        if y2 == y3:
            y12 = y2 
            
            
            
        
if l1 >l2:
    
    x1 = x1
    x2 = x3
    x3 = x4
    y1 = y1
    y2 = y3
    y3 = y4
    
    if abs(1-l2/l4) < 0.3 :
        
        if x1>x2:
            x11 = x1 - l2/2
            
        if x1<x2:
            x11 = x1 + l2/2
            
        if x1 == x2:
            x11 = x1 
            
        if y1>y2:
            y11 = y1 - l2/2
            
        if y1<y2:
            y11 = y1 + l2/2
            
        if y1 == y2:
            y11 = y1 
            
            
        if x2>x3:
            x12 = x2 - l4/2
            
        if x2<x3:
            x12 = x2 + l4/2
            
        if x2 == x3:
            x12 = x2 
            
        if y2>y3:
            y12 = y2 - l4/2
            
        if y2<y3:
            y12 = y2 + l4/2
            
        if y2 == y3:
            y12 = y2 
            
plt.plot(x,y)

plt.plot([x11,x12],[y11,y12])

>Solution :

That is way too complicated. You can just draw the lines going through the center of the segments like so (note that I added a copy of x[0] and y[0] as x[4] and y[4] for simplicity):

import matplotlib.pyplot as plt

x = [4,4,-4,-4]

y = [8,-5,-5,8]
            
x = x + [x[0]]
y = y + [y[0]]
plt.plot(x,y)

for i in range(2):
    plt.plot([(x[i]+x[i+1])/2, (x[i+2]+x[i+3])/2], [(y[i]+y[i+1])/2, (y[i+2]+y[i+3])/2])