Opencv Python Cropping Image

I've created black image, than I drew a red rectangle into this image. Afterwards I cropped this image and drew a another rectangle into the cropped image using the command. cv2.r

Solution 1:

crop = image[100:300,100:300] creates a view on the original image instead of a new object. Modifying that view will modify the underlying original image. See http://scipy-cookbook.readthedocs.io/items/ViewsVsCopies.html for more details.

You can resolve this issue by creating a copy when cropping: crop = image[100:300,100:300].copy().

Note: image[100:300,100:300] parameters are y: y+h, x: x+w not x: x+w, y: y+h

Solution 2:

if you want to save the cropped image, just add this code:

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

after cv2.imshow("Cropped", roi)

I hope this helps.

Solution 3:

you can easily crop the image in python by using

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

In order to get the two points you can call cv2.setMouseCallback("image", mouse_crop). The function is something like this

defmouse_crop(event, x, y, flags, param):
    # grab references to the global variablesglobal 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 beingif event == cv2.EVENT_LBUTTONDOWN:
        x_start, y_start, x_end, y_end = x, y, x, y
        cropping = True# Mouse is Movingelif event == cv2.EVENT_MOUSEMOVE:
        if cropping == True:
            x_end, y_end = x, y

    # if the left mouse button was releasedelif 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)]

        iflen(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)

You can get details from here : Mouse Click and Cropping using Python