OpenCV Python裁剪圖像

Question

我創建了黑色圖像，然后在該圖像中繪制了一個紅色矩形。 之后，我裁剪了該圖像，並使用命令在裁剪后的圖像中繪制了另一個矩形。 cv2.rectangle(crop,(50,50),(150,150),(0,0,255),3)

為什么最后顯示第二個矩形時，它會出現在原始圖像中？ 我希望只能看到第一個矩形。

import cv2
import numpy as np

#create image
image = np.zeros((400,400,3), np.uint8)

#draw rectangle into original image
cv2.rectangle(image,(100,100),(300,300),(0,0,255),3)

#crop image
crop = image[100:300,100:300]

#draw rectangle into cropped image
cv2.rectangle(crop,(50,50),(150,150),(0,0,255),3)
cv2.imshow('Result', image)
cv2.waitKey()    

cv2.destroyAllWindows()

Answer 1

crop = image[100:300,100:300]在原始圖像上創建視圖 ，而不是新對象。 修改該視圖將修改基礎原始圖像。 有關更多詳細信息，請參見http://scipy-cookbook.readthedocs.io/items/ViewsVsCopies.html 。

您可以通過在裁剪時創建一個副本來解決此問題： crop = image[100:300,100:300].copy() 。

注意： image[100:300,100:300]參數為y: y+h, x: x+w not x: x+w, y: y+h

Answer 2

如果要保存裁剪的圖像，只需添加以下代碼：

cv2.imwrite("Cropped.jpg", roi)

after cv2.imshow("Cropped", roi)

我希望這有幫助。

Answer 3

您可以使用輕松在python中裁剪圖像

roi = oriImage[refPoint[0][1]:refPoint[1][1], refPoint[0][0]:refPoint[1][0]]

為了得到兩點，可以調用cv2.setMouseCallback("image", mouse_crop) 。 該功能是這樣的

def mouse_crop(event, x, y, flags, param):
    # grab references to the global variables
    global x_start, y_start, x_end, y_end, cropping

    # if the left mouse button was DOWN, start RECORDING
    # (x, y) coordinates and indicate that cropping is being
    if event == cv2.EVENT_LBUTTONDOWN:
        x_start, y_start, x_end, y_end = x, y, x, y
        cropping = True

    # Mouse is Moving
    elif event == cv2.EVENT_MOUSEMOVE:
        if cropping == True:
            x_end, y_end = x, y

    # if the left mouse button was released
    elif event == cv2.EVENT_LBUTTONUP:
        # record the ending (x, y) coordinates
        x_end, y_end = x, y
        cropping = False # cropping is finished

        refPoint = [(x_start, y_start), (x_end, y_end)]

        if len(refPoint) == 2: #when two points were found
            roi = oriImage[refPoint[0][1]:refPoint[1][1], refPoint[0][0]:refPoint[1][0]]
            cv2.imshow("Cropped", roi)

您可以從此處獲取詳細信息： 使用Python進行鼠標單擊和裁剪