find a white rhombus bigger than 500 pixels, and highlight it in python in python in python

You can find a white rhombus using the following steps:

  1. Load the image in Python using any image processing library like Pillow or OpenCV
  2. Convert the image to grayscale
  3. Apply edge detection algorithm like Canny to detect edges in the image
  4. Using Hough line transformation, detect all the lines in the image
  5. Filter out all the lines with angles close to 45 degrees or 135 degrees to get possible rhombus sides
  6. Using endpoints of these lines, find intersection points to get possible rhombus vertices
  7. Calculate the distances between the vertices and filter out all the rhombuses with sides smaller than 500 pixels.
  8. Once you have found a rhombus, you can draw a rectangle around it to highlight it.

Here's the code that implements these steps:

main.py
import cv2

# Load the image
image = cv2.imread('image.jpg')

# Convert the image to grayscale
gray = cv2.cvtColor(image, cv2.COLOR_BGR2GRAY)

# Apply Canny edge detection algorithm
edges = cv2.Canny(gray, 50, 200)

# Apply Hough line transformation to detect lines in the image
lines = cv2.HoughLines(edges, 1, np.pi/180, 200)

# Filter out all the lines with angles close to 45 or 135 degrees
filtered_lines = []
for line in lines:
    rho, theta = line[0]
    angle = np.degrees(theta)
    if (np.abs(45 - angle) < 10) or (np.abs(135 - angle) < 10):
        filtered_lines.append(line)

# Find intersection points to get possible rhombus vertices
vertices = []
for i in range(len(filtered_lines)):
    for j in range(i+1, len(filtered_lines)):
        rho1, theta1 = filtered_lines[i][0]
        rho2, theta2 = filtered_lines[j][0]
        A = np.array([
            [np.cos(theta1), np.sin(theta1)],
            [np.cos(theta2), np.sin(theta2)]
        ])
        b = np.array([
            [rho1],
            [rho2]
        ])
        intersection = np.linalg.solve(A, b)
        intersection = np.round(intersection).astype(int)
        vertices.append(intersection)

# Calculate the distances between the vertices and filter out all the rhombuses with sides smaller than 500 pixels.
for i in range(len(vertices)):
    for j in range(i+1, len(vertices)):
        for k in range(j+1, len(vertices)):
            for l in range(k+1, len(vertices)):
                side1 = np.linalg.norm(vertices[i] - vertices[j])
                side2 = np.linalg.norm(vertices[j] - vertices[k])
                side3 = np.linalg.norm(vertices[k] - vertices[l])
                side4 = np.linalg.norm(vertices[l] - vertices[i])
                sides = [side1, side2, side3, side4]
                if all(side > 500 for side in sides):
                    # Found a rhombus, draw a rectangle around it
                    cv2.rectangle(image, tuple(vertices[i]), tuple(vertices[k]), (0, 0, 255), 2)

# Display the image
cv2.imshow('image', image)
cv2.waitKey(0)
cv2.destroyAllWindows()
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Note: This code assumes that the white rhombus has black background in the image. If the background is white, then you need to invert the image first before applying edge detection algorithm.

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