How to get the boundary vertices after image chunking in Python?

Python efficiently extracts image chunking boundary vertices

In image processing, it is often necessary to block the image and obtain the boundary vertices of each block. Assume that the single-channel image has been chunked, the block value is incremented from 1 to form an h×m grid (the value within the block is the same). This article will introduce how to efficiently extract these boundary vertices using Python.

First, understand the image block structure. Assuming that chunking is completed, a grid with different values ​​can be obtained, which can be processed using OpenCV and NumPy libraries.

Extract boundary vertices steps:

1. Image Reading and Preprocessing : Use OpenCV to read images and convert them to single-channel grayscale. If chunking is completed, use the resulting image directly.

2. Block boundary recognition : traversing the image to recognize different block boundaries. Blocks can be identified and marked using connectivity domain analysis (such as OpenCV's cv2.connectedComponents ).

3. Boundary Vertex Extraction : Iterates over the boundary pixels of each block and records the vertex coordinates. OpenCV's cv2.findContours function finds the block contour and extracts vertices from it.

The following code example demonstrates how to implement using OpenCV and NumPy:

 import cv2
import numpy as np

# Assume that chunking is completed img = cv2.imread('segmented_image.png', cv2.IMREAD_GRAYSCALE)

# Connection domain analysis num_labels, labels = cv2.connectedComponents(img)

# traverse each connected domain for label in range(1, num_labels):
    # Create mask mask = np.zeros_like(img)
    mask[labels == label] = 255

    # Find contours, _ = cv2.findContours(mask, cv2.RETR_EXTERNAL, cv2.CHAIN_APPROX_SIMPLE)

    # Get the first contour (assuming there is only one contour per block)
    contour = contours[0]

    # Get boundary vertices = contour.reshape(-1, 2)

    # output vertex coordinate print(f"block {label} boundary vertex:")
    for vertex in vertices:
        print(vertex)

This code uses connectivity domain analysis and contour detection to extract boundary vertices of each block. The code can be adjusted and optimized according to actual needs. OpenCV and NumPy provide powerful image processing functions to facilitate and efficiently extract image chunking boundary vertices.

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