在python中检测图像中的彩色点？答案

【问题标题】：Detect colorful dots in image in python?在python中检测图像中的彩色点？
【发布时间】：2020-08-21 05:58:10
【问题描述】：

我正在尝试检测白色/灰色背景上的彩色点。这些点是 3 种不同颜色（黄色、紫色、蓝色）的不同大小。这是原图：

我将图像转换为 HSV 并找到每个图像的下限和上限，然后应用轮廓检测来找到这些点。以下代码检测到大部分点：

import cv2
import numpy as np
from matplotlib import pyplot as plt
img = cv2.imread('image1_1.png')

hsv = cv2.cvtColor(img, cv2.COLOR_BGR2HSV)

lower_yellow = np.array([22,25,219])
upper_yellow = np.array([25,75,225])

lower_purple = np.array([141,31,223])
upper_purple = np.array([143,83,225])

lower_blue = np.array([92,32,202])
upper_blue = np.array([96,36,208])

mask_blue = cv2.inRange(hsv, lower_blue, upper_blue)
mask_purple = cv2.inRange(hsv, lower_purple, upper_purple)
mask_yellow = cv2.inRange(hsv, lower_yellow, upper_yellow)

res_blue = cv2.bitwise_and(img,img, mask=mask_blue)
res_purple = cv2.bitwise_and(img,img, mask=mask_purple)
res_yellow = cv2.bitwise_and(img,img, mask=mask_yellow)

gray_blue = cv2.cvtColor(res_blue, cv2.COLOR_BGR2GRAY)
gray_purple = cv2.cvtColor(res_purple, cv2.COLOR_BGR2GRAY)
gray_yellow = cv2.cvtColor(res_yellow, cv2.COLOR_BGR2GRAY)

_,thresh_blue = cv2.threshold(gray_blue,10,255,cv2.THRESH_BINARY)
_,thresh_purple = cv2.threshold(gray_purple,10,255,cv2.THRESH_BINARY)
_,thresh_yellow = cv2.threshold(gray_yellow,10,255,cv2.THRESH_BINARY)

contours_blue, hierarhy1 = cv2.findContours(thresh_blue,cv2.RETR_TREE,cv2.CHAIN_APPROX_SIMPLE)
contours_purple, hierarhy2 = cv2.findContours(thresh_purple,cv2.RETR_TREE,cv2.CHAIN_APPROX_SIMPLE)
contours_yellow, hierarhy3 = cv2.findContours(thresh_yellow,cv2.RETR_TREE,cv2.CHAIN_APPROX_SIMPLE)

result = img.copy()
cv2.drawContours(result, contours_blue, -1, (0, 0, 255), 2)
cv2.drawContours(result, contours_purple, -1, (0, 0, 255), 2)
cv2.drawContours(result, contours_yellow, -1, (0, 0, 255), 2)
cv2.imwrite("_allContours.jpg", result)

以下是检测到的轮廓：

问题是一些彩色点没有被检测到。我理解通过微调颜色范围（上下）可以检测到更多的点。但这非常耗时，并且不能推广到类似的图像。例如，下面的图像看起来与上面的第一张图像相似，并且具有相同的彩色点，但背景略有不同，一旦我通过上面的代码运行它，它甚至无法检测到一个点。我在正确的轨道上吗？为了解决这个问题，是否有更可扩展和更可靠的解决方案，无需调整颜色参数？这是我尝试的另一张图片：

【问题讨论】：

标签： python opencv contour cv2 opencv-contour

【解决方案1】：

我建议在 Python/OpenCV 中简单地使用 AdaptiveThreshold

import cv2
import numpy as np

# read image
img = cv2.imread("dots.png")

# convert img to grayscale
gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)

# do adaptive threshold on gray image
thresh = cv2.adaptiveThreshold(gray, 255, cv2.ADAPTIVE_THRESH_MEAN_C, cv2.THRESH_BINARY, 25, 6)

# write results to disk
cv2.imwrite("dots_thresh.jpg", thresh)

# display it
cv2.imshow("thresh", thresh)
cv2.waitKey(0)

【讨论】：