如何正确使用cv2.fillPoly函数？多多边形填充报错求助

尝试用cv2.fillPoly同时填充三角形和梯形两个多边形，代码如下：

# Import necessary libraries
import cv2
import numpy as np

# Read an image
img = np.zeros((500,500))

# Define an array of endpoints of triangle
points = np.array([[[160, 130], [350, 130], [250, 300]],[[160, 30], [50, 30], [80, 130],[100, 130]]],dtype=object)

# Use fillPoly() function and give input as
# image, end points,color of polygon
# Here color of polygon will blue
for i in range(len(points)):
    cv2.fillPoly(img, pts=[points[i]], color=(255, 0, 0))
#cv2.fillPoly(img, pts=[points[1]], color=(255, 0, 0))


# Displaying the image
cv2.imshow("Triangle", img)

# wait for the user to press any key to
# exit window
cv2.waitKey(0) 

# Closing all open windows
cv2.destroyAllWindows()

运行后报错：

/var/folders/hh/phtw2ldx7gj88krjgwdbz9680000gn/T/ipykernel_1755/1373141779.py:9: VisibleDeprecationWarning: Creating an ndarray from ragged nested sequences (which is a list-or-tuple of lists-or-tuples-or ndarrays with different lengths or shapes) is deprecated. If you meant to do this, you must specify 'dtype=object' when creating the ndarray.
  points = np.array([[[160, 130], [350, 130], [250, 300]],[[160, 30], [50, 30], [80, 130],[100, 130]]])
---------------------------------------------------------------------------
error                                     Traceback (most recent call last)
Input In [35], in <cell line: 14>()
     11 # Use fillPoly() function and give input as
     12 # image, end points,color of polygon
     13 # Here color of polygon will blue
     14 for i in range(len(points)):
---&gt; 15     cv2.fillPoly(img, pts=[points[i]], color=(255, 0, 0))
     16 #cv2.fillPoly(img, pts=[points[1]], color=(255, 0, 0))
     17 
     18 
     19 # Displaying the image
     20 cv2.imshow("Triangle", img)

error: OpenCV(4.6.0) :-1: error: (-5:Bad argument) in function 'fillPoly'
&gt; Overload resolution failed:
&gt;  - Can't parse 'pts'. Sequence item with index 0 has a wrong type
&gt;  - Can't parse 'pts'. Sequence item with index 0 has a wrong type

问题核心：两个多边形顶点数不同（3个和4个），使用dtype=object的numpy数组存储导致fillPoly无法解析pts参数。

OpenCV的fillPoly要求每个多边形的顶点数组必须是固定维度的int32类型numpy数组，无需将不同顶点数的多边形塞进同一个object类型数组，直接用Python列表管理多个多边形即可。

修复后的代码 #

import cv2
import numpy as np

# 创建单通道空白图像（uint8类型符合OpenCV图像格式要求）
img = np.zeros((500, 500), dtype=np.uint8)

# 用Python列表存储两个多边形，每个多边形转为shape=(N,1,2)的int32数组
polygons = [
    # 三角形：转int32后调整形状为(3,1,2)
    np.array([[160, 130], [350, 130], [250, 300]], dtype=np.int32).reshape((-1, 1, 2)),
    # 梯形：转int32后调整形状为(4,1,2)
    np.array([[160, 30], [50, 30], [80, 130], [100, 130]], dtype=np.int32).reshape((-1, 1, 2))
]

# 遍历填充每个多边形
for poly in polygons:
    cv2.fillPoly(img, pts=[poly], color=255)  # 单通道用灰度值，彩色图像可改为(255,0,0)

# 显示结果
cv2.imshow("Polygons", img)
cv2.waitKey(0)
cv2.destroyAllWindows()

关键修复细节 #

• 放弃dtype=object的numpy数组，改用Python列表存储不同顶点数的多边形，避免数组形状不统一问题。
• 每个多边形顶点数组必须是np.int32类型，且形状为(顶点数量, 1, 2)，通过reshape((-1,1,2))可自动适配任意顶点数。
• 图像数组指定dtype=np.uint8，符合OpenCV处理图像的标准格式，避免类型不兼容问题。

内容的提问来源于stack exchange，提问作者Alain Michael Janith Schroter