EP08_07 — 🟡 Salt-and-Pepper Noise Removal and Object Measurement

8.14.7.1 📋 Implementation Guidelines

1. Input: read two integers \(H\) and \(W\) (image height and width) from the first line, followed by \(H\) lines containing the binary matrix with pixels 0 and 1 separated by spaces.

2. Morphological Filtering: apply a chain of Opening (to eliminate salt noise in the background) followed by Closing (to fill pepper noise inside objects) using a \(3 \times 3\) structuring element.

3. Printing the Cleaned Image: print the resulting matrix with values 0 and 1 separated by spaces.

4. Geometric Measurements: for each object identified in the cleaned matrix, extract:

• id: sequential numeric identifier (reassigned after sorting);

• area: area calculated via contour (cv2.contourArea);

• perimeter: contour perimeter (cv2.arcLength);

• cx, cy: center of mass (centroid via cv2.moments);

• x, y, w, h: coordinates of the bounding rectangle (cv2.boundingRect);

• circularity: circularity given by \(\frac{4 \pi \cdot \text{area}}{\text{perimeter}^2}\);

• solidity: solidity given by the ratio \(\frac{\text{area}}{\text{convex hull area}}\);

• vertices: approximate number of polygon vertices (cv2.approxPolyDP with \(\epsilon = 0.02 \times \text{perimeter}\)).

5. Sorting and Output: sort objects in ascending order by the \(X\) position of the bounding rectangle (bbox[0]); in case of a tie, use the \(Y\) position (bbox[1]). Reassign ids from \(1\) to \(N\) and print the formatted table.
   • For sorting, use medidas.sort(key=lambda m: (m['bbox'][1], m['bbox'][0])), with medidas = mm.measure(img).

8.14.7.2 📌 Constraints and Sorting Rules

• Object Sorting Rule:

medidas.sort(key=lambda m: (m['bbox'][0], m['bbox'][1]))

• Area Difference: The area calculated by OpenCV (cv2.contourArea) measures the area of the continuous polygon delimited by the centers of border pixels, resulting in numeric values smaller than the simple discrete count of 1 pixels (np.sum).

8.14.7.3 🧠 Theoretical Foundation

8.14.7.4 📌 Examples

%%writefile EP08_07.py
# Python code

Overwriting EP08_07.py

TestSuite("EP08_07.py").run()

✔️ EP08_07.cases already exists in casos/
📋 4 case(s) loaded from casos/EP08_07.cases

🔍 Testing Python: EP08_07.py
⚠️ EP08_07.py: Empty file (fewer than 3 lines). Tests skipped.