python - 找到阈值图像的轮廓

Question

我想检测图像的轮廓。并检查这些轮廓是否在另一幅图像中

Answer 1

您可以进行透视扭曲以将一个图像与另一个对齐。将两者都转换为 HSV 并获得饱和 channel 。然后阈值它们并获得它们之间的绝对差异。然后得到轮廓，最后得到轮廓的边界框，绘制在第一张图像上。以下是如何使用 Python/OpenCV 做到这一点。请注意，我没有安装 SIFT，所以我将使用 ORB 来代替它。

输入 1(引用图像):



输入 2(要扭曲/对齐的图像):

import cv2
import numpy as np


MAX_FEATURES = 500
GOOD_MATCH_PERCENT = 0.15


def alignImages(im1, im2):

  # im2 is reference and im1 in to be warped to match im2
  # note: numbering is swapped in function

  # Convert images to grayscale
  im1Gray = cv2.cvtColor(im1, cv2.COLOR_BGR2GRAY)
  im2Gray = cv2.cvtColor(im2, cv2.COLOR_BGR2GRAY)

  # Detect ORB features and compute descriptors.
  orb = cv2.ORB_create(MAX_FEATURES)
  keypoints1, descriptors1 = orb.detectAndCompute(im1Gray, None)
  keypoints2, descriptors2 = orb.detectAndCompute(im2Gray, None)

  # Match features.
  matcher = cv2.DescriptorMatcher_create(cv2.DESCRIPTOR_MATCHER_BRUTEFORCE_HAMMING)
  matches = matcher.match(descriptors1, descriptors2, None)

  # Sort matches by score
  matches.sort(key=lambda x: x.distance, reverse=False)

  # Remove not so good matches
  numGoodMatches = int(len(matches) * GOOD_MATCH_PERCENT)
  matches = matches[:numGoodMatches]

  # Draw top matches
  imMatches = cv2.drawMatches(im1, keypoints1, im2, keypoints2, matches, None)
  cv2.imwrite("pipes_matches.png", imMatches)

  # Extract location of good matches
  points1 = np.zeros((len(matches), 2), dtype=np.float32)
  points2 = np.zeros((len(matches), 2), dtype=np.float32)

  for i, match in enumerate(matches):
    points1[i, :] = keypoints1[match.queryIdx].pt
    points2[i, :] = keypoints2[match.trainIdx].pt

  # Find homography
  h, mask = cv2.findHomography(points1, points2, cv2.RANSAC)

  # Use homography
  height, width, channels = im2.shape
  im1Reg = cv2.warpPerspective(im1, h, (width, height))

  return im1Reg, h


if __name__ == '__main__':

  # Read reference image
  refFilename = "pipes1.jpg"
  print("Reading reference image : ", refFilename)
  imReference = cv2.imread(refFilename, cv2.IMREAD_COLOR)

  # Read image to be aligned
  imFilename = "pipes2.jpg"
  print("Reading image to align : ", imFilename);  
  im = cv2.imread(imFilename, cv2.IMREAD_COLOR)

  # Aligned image will be stored in imReg. 
  # The estimated homography will be stored in h. 
  imReg, h = alignImages(im, imReference)

  # Print estimated homography
  print("Estimated homography : \n",  h)

  # Convert images to HSV and get saturation channel
  refSat = cv2.cvtColor(imReference, cv2.COLOR_BGR2HSV)[:,:,1]
  imSat = cv2.cvtColor(imReg, cv2.COLOR_BGR2HSV)[:,:,1]

  # Otsu threshold
  refThresh = cv2.threshold(refSat, 0, 255, cv2.THRESH_BINARY+cv2.THRESH_OTSU)[1]
  imThresh = cv2.threshold(imSat, 0, 255, cv2.THRESH_BINARY+cv2.THRESH_OTSU)[1]

  # apply morphology open and close
  kernel = cv2.getStructuringElement(cv2.MORPH_ELLIPSE, (7,7))
  refThresh = cv2.morphologyEx(refThresh, cv2.MORPH_OPEN, kernel, iterations=1)
  refThresh = cv2.morphologyEx(refThresh, cv2.MORPH_CLOSE, kernel, iterations=1).astype(np.float64)
  imThresh = cv2.morphologyEx(imThresh, cv2.MORPH_OPEN, kernel, iterations=1).astype(np.float64)
  imThresh = cv2.morphologyEx(imThresh, cv2.MORPH_CLOSE, kernel, iterations=1)

  # get absolute difference between the two thresholded images
  diff = np.abs(cv2.add(imThresh,-refThresh))

  # apply morphology open to remove thin lines caused by slight misalignment of the two images
  kernel = cv2.getStructuringElement(cv2.MORPH_ELLIPSE, (13,13))
  diff_cleaned = cv2.morphologyEx(diff, cv2.MORPH_OPEN, kernel, iterations=1).astype(np.uint8)

  # Filter using contour area and draw bounding boxes that do not touch the sides of the image
  cnts = cv2.findContours(diff_cleaned, cv2.RETR_EXTERNAL, cv2.CHAIN_APPROX_SIMPLE)
  cnts = cnts[0] if len(cnts) == 2 else cnts[1]
  result = imReference.copy()
  for c in cnts:
      x,y,w,h = cv2.boundingRect(c)
      cv2.rectangle(result, (x, y), (x+w, y+h), (0, 0, 255), 2)

  # show images
  cv2.imshow('reference', imReference)
  cv2.imshow('image', im)
  cv2.imshow('image_aligned', imReg)
  cv2.imshow('refThresh', refThresh)
  cv2.imshow('imThresh', imThresh)
  cv2.imshow('diff', diff)
  cv2.imshow('diff_cleaned', diff_cleaned)
  cv2.imshow('result', result)
  cv2.waitKey()

  # save images
  cv2.imwrite('pipes2_aligned.jpg', imReg)
  cv2.imwrite('pipes_diff.png', diff_cleaned)
  cv2.imwrite('pipes_result.png', result)

匹配图像:



图像 2(透视)与图像 1 对齐:



绝对差异图像(已清理):



结果: