[英]Detecting Nested Shape in opencv
我需要檢測 opencv 中的嵌套形狀,但似乎即使使用層次結構我也可以做到
edges = cv2.Canny(img,50,200)
contours,hierarchy = cv2.findContours(edges, cv2.RETR_TREE,cv2.CHAIN_APPROX_SIMPLE)
hierarchy = hierarchy[0] # get the actual inner list of hierarchy descriptions
for comp in contours:
currentCont = comp[0]
currentHie = hierarchy[1]
x,y,w,h = cv2.boundingRect(currentContour)
if ( currentHierarchy[1] < 0 )
these are the innermost child components
cv2.rectangle(img,(x,y),(x+w,y+h),(0,0,255),3)
cv2.putText(img, "nes", (x, y), cv2.FONT_HERSHEY_COMPLEX, 0.5, (0, 0, 0), 2)
cv2.drawContours(img, [currentCont], -1, (0, 255, 0), 1)
cv2.waitKey()
cv2.imshow("image",img)
cv2.waitKey(0)
cv2.destroyAllWindows()
我將向您展示如何找到嵌套的最內部輪廓。
我認為有比您的樣本更復雜的結構,您必須對其進行分類。
我建議不要使用cv2.Canny
,因為它會創建更多的層次結構。
看看使用cv2.imshow("edges", edges)
和cv2.waitKey()
。
您可能只是反轉極性以獲得黑色背景上的白色三角形。
img = 255 - img
有一個小錯誤(在循環內):
您正在使用: currentHierarchy = hierarchy[1]
而不是: currentHierarchy = component[1]
查找嵌套輪廓:
從最內部的輪廓開始。
最內部的輪廓是沒有“第一個孩子”的輪廓。
檢查currentHierarchy[2] < 0
是否。
所有內部輪廓都將有一個父輪廓。
原因是每個三角形應用兩個(嵌套)輪廓:
我們需要獲取父輪廓,並檢查父輪廓是否有父輪廓。
具有祖父母的內部三角形是嵌套三角形。
這是完整的代碼示例:
import numpy as np
import cv2
img = cv2.imread('triangles.png', cv2.IMREAD_GRAYSCALE) # Read input image as grayscale,
# edges = cv2.Canny(img, 50, 200)
# Invert polarity of img, instead of using Canny - we need the contours to be white.
img = 255 - img
contours, hierarchy = cv2.findContours(img, cv2.RETR_TREE, cv2.CHAIN_APPROX_SIMPLE)
hierarchy = hierarchy[0] # get the actual inner list of hierarchy descriptions
img = cv2.cvtColor(img, cv2.COLOR_GRAY2BGR) # Convert image to BGR, for using colored text.
for component in zip(contours, hierarchy):
currentContour = component[0]
#currentHierarchy = hierarchy[1] # Why ?
currentHierarchy = component[1]
approx = cv2.approxPolyDP(currentContour, 0.01 * cv2.arcLength(currentContour, True), True)
x = approx.ravel()[0]
y = approx.ravel()[1] - 5
# https://docs.opencv.org/master/d9/d8b/tutorial_py_contours_hierarchy.html
# Hierarchy Representation in OpenCV
# Each contour has its own information regarding what hierarchy it is, who is its child, who is its parent etc.
# OpenCV represents it as an array of four values : [Next, Previous, First_Child, Parent]
#if (currentHierarchy[1] < 0) and len(approx) == 3:
if (currentHierarchy[2] < 0) and len(approx) == 3:
# These are the innermost child components
parent_idx = currentHierarchy[3] # Get the index of the parent contour
parent_hier = hierarchy[parent_idx] # Get the hierarchy of the parent.
if parent_hier[3] >= 0:
# Contour is nested only if the parent has a parent.
cv2.putText(img, "Nested", (x, y), cv2.FONT_HERSHEY_COMPLEX, 0.5, (255, 0, 0), 2)
cv2.drawContours(img, [currentContour], -1, (0, 255, 0), 1)
cv2.waitKey(1000)
cv2.imshow("image", img)
cv2.waitKey()
cv2.destroyAllWindows()
聲明:本站的技術帖子網頁,遵循CC BY-SA 4.0協議,如果您需要轉載,請注明本站網址或者原文地址。任何問題請咨詢:yoyou2525@163.com.