OpenCV 小ネタ集2 (cv2 の Contour 抽出手順)

Sorting Contours

import cv2
import numpy as np
import matplotlib.pyplot as plt

def cv2_imshow(title, image):
    plt.imshow(cv2.cvtColor(image.astype(np.uint8), cv2.COLOR_BGR2RGB))
    plt.title(title)
    # as opencv loads in BGR format by default, we want to show it in RGB.
    plt.show()

# Load our image
image = cv2.imread('images/bunchofshapes.jpg')
cv2_imshow('0 - Original Image', image)

# Create a black image with same dimensions as our loaded image
blank_image = np.zeros((image.shape[0], image.shape[1], 3))

# Create a copy of our original image
orginal_image = image

# Grayscale our image
gray = cv2.cvtColor(image,cv2.COLOR_BGR2GRAY)

# Find Canny edges
edged = cv2.Canny(gray, 50, 200)
cv2_imshow('1 - Canny Edges', edged)

# Find contours and print how many were found
contours, hierarchy = cv2.findContours(edged.copy(), cv2.RETR_EXTERNAL, cv2.CHAIN_APPROX_NONE)
print ("Number of contours found = ", len(contours))

#Draw all contours
cv2.drawContours(blank_image, contours, -1, (0,255,0), 3)
cv2_imshow('2 - All Contours over blank image', blank_image)

# Draw all contours over blank image
cv2.drawContours(image, contours, -1, (0,255,0), 3)
cv2_imshow('3 - All Contours', image)


import cv2
import numpy as np

# Function we'll use to display contour area
# cv2.contourArea で contour の面積を取得

def get_contour_areas(contours):
    # returns the areas of all contours as list
    all_areas = []
    for cnt in contours:
        area = cv2.contourArea(cnt)
        all_areas.append(area)
    return all_areas

# Load our image
image = cv2.imread('images/bunchofshapes.jpg')
orginal_image = image

# Let's print the areas of the contours before sorting
print("Contor Areas before sorting") 
print(get_contour_areas(contours))

# Sort contours large to small
sorted_contours = sorted(contours, key=cv2.contourArea, reverse=True)
#sorted_contours = sorted(contours, key=cv2.contourArea, reverse=True)[:3]

print("Contor Areas after sorting"), 
print(get_contour_areas(sorted_contours))

# Iterate over our contours and draw one at a time
for c in sorted_contours:
    cv2.drawContours(orginal_image, [c], -1, (255,0,0), 9)
    cv2_imshow('Contours by area', orginal_image)

• Contour から中心点を抽出

import cv2
import numpy as np

# Functions we'll use for sorting by position

def x_cord_contour(contours):
    #Returns the X cordinate for the contour centroid
    if cv2.contourArea(contours) > 10:
        M = cv2.moments(contours)
        return (int(M['m10']/M['m00']))
    else:
        pass

    
def label_contour_center(image, c):
    # Places a red circle on the centers of contours
    M = cv2.moments(c)
    cx = int(M['m10'] / M['m00'])
    cy = int(M['m01'] / M['m00'])
 
    # Draw the countour number on the image
    cv2.circle(image,(cx,cy), 10, (0,0,255), -1)
    return image


# Load our image
image = cv2.imread('images/bunchofshapes.jpg')
orginal_image = image.copy()


# Computer Center of Mass or centroids and draw them on our image
for (i, c) in enumerate(contours):
    orig = label_contour_center(image, c)
 
cv2_imshow("4 - Contour Centers ", image)

# Sort by left to right using our x_cord_contour function
contours_left_to_right = sorted(contours, key = x_cord_contour, reverse = False)


# Labeling Contours left to right
for (i,c)  in enumerate(contours_left_to_right):
    cv2.drawContours(orginal_image, [c], -1, (0,0,255), 3)  
    M = cv2.moments(c)
    cx = int(M['m10'] / M['m00'])
    cy = int(M['m01'] / M['m00'])
    cv2.putText(orginal_image, str(i+1), (cx, cy), cv2.FONT_HERSHEY_SIMPLEX, 1, (0, 255, 0), 2)
    cv2_imshow('6 - Left to Right Contour', orginal_image)
    (x, y, w, h) = cv2.boundingRect(c)  
    
    # Let's now crop each contour and save these images
    cropped_contour = orginal_image[y:y + h, x:x + w]
    image_name = "output_shape_number_" + str(i+1) + ".jpg"
    print(image_name)
    cv2.imwrite(image_name, cropped_contour)

• Contour の抽出

import cv2
import numpy as np

# Functions we'll use for sorting by position

def x_cord_contour(contours):
    #Returns the X cordinate for the contour centroid
    if cv2.contourArea(contours) > 10:
        M = cv2.moments(contours)
        return (int(M['m10']/M['m00']))
    else:
        pass

    
def label_contour_center(image, c):
    # Places a red circle on the centers of contours
    M = cv2.moments(c)
    cx = int(M['m10'] / M['m00'])
    cy = int(M['m01'] / M['m00'])
 
    # Draw the countour number on the image
    cv2.circle(image,(cx,cy), 10, (0,0,255), -1)
    return image


# Load our image
image = cv2.imread('images/bunchofshapes.jpg')
orginal_image = image.copy()


# Computer Center of Mass or centroids and draw them on our image
for (i, c) in enumerate(contours):
    orig = label_contour_center(image, c)
 
cv2_imshow("4 - Contour Centers ", image)

# Sort by left to right using our x_cord_contour function
contours_left_to_right = sorted(contours, key = x_cord_contour, reverse = False)


# Labeling Contours left to right
for (i,c)  in enumerate(contours_left_to_right):
    cv2.drawContours(orginal_image, [c], -1, (0,0,255), 3)  
    M = cv2.moments(c)
    cx = int(M['m10'] / M['m00'])
    cy = int(M['m01'] / M['m00'])
    cv2.putText(orginal_image, str(i+1), (cx, cy), cv2.FONT_HERSHEY_SIMPLEX, 2, (0, 255, 0), 4)
    cv2_imshow('6 - Left to Right Contour', orginal_image)
    (x, y, w, h) = cv2.boundingRect(c)  
    
    # Let's now crop each contour and save these images
    cropped_contour = orginal_image[y:y + h, x:x + w]
    image_name = "output_shape_number_" + str(i+1) + ".jpg"
    print(image_name)
    cv2.imwrite(image_name, cropped_contour)