python - 如何在 Python 中使用 OpenCV 的 connectedComponentsWithStats？

Question

我正在寻找如何在 Python 中使用 OpenCV 的 connectedComponentsWithStats() 函数的示例。请注意，这仅适用于 OpenCV 3 或更高版本。官方文档仅显示了 C++ 的 API，即使该函数在为 Python 编译时存在。我在网上的任何地方都找不到。

Answer 1

函数的工作原理如下:

# Import the cv2 library
import cv2
# Read the image you want connected components of
src = cv2.imread('/directorypath/image.bmp')
# Threshold it so it becomes binary
ret, thresh = cv2.threshold(src,0,255,cv2.THRESH_BINARY+cv2.THRESH_OTSU)
# You need to choose 4 or 8 for connectivity type
connectivity = 4  
# Perform the operation
output = cv2.connectedComponentsWithStats(thresh, connectivity, cv2.CV_32S)
# Get the results
# The first cell is the number of labels
num_labels = output[0]
# The second cell is the label matrix
labels = output[1]
# The third cell is the stat matrix
stats = output[2]
# The fourth cell is the centroid matrix
centroids = output[3]

标签是输入图像大小的矩阵，其中每个元素的值等于其标签。

Stats 是函数计算的统计数据矩阵。它的长度等于标签的数量，宽度等于统计的数量。它可以与 OpenCV 文档一起使用:

Statistics output for each label, including the background label, see below for available statistics. Statistics are accessed via stats[label, COLUMN] where available columns are defined below.

• cv2.CC_STAT_LEFT The leftmost (x) coordinate which is the inclusive start of the bounding box in the horizontal direction.
• cv2.CC_STAT_TOP The topmost (y) coordinate which is the inclusive start of the bounding box in the vertical direction.
• cv2.CC_STAT_WIDTH The horizontal size of the bounding box
• cv2.CC_STAT_HEIGHT The vertical size of the bounding box
• cv2.CC_STAT_AREA The total area (in pixels) of the connected component

质心 是一个矩阵，其中包含每个质心的 x 和 y 位置。此矩阵中的行对应于标签编号。