Python cv2 90:90 纵横比矩形裁剪图像

Question

I'm writing a Programm to crop inmages and my problem is I want that rectangle to have a specific aspect ratio (90:90) and is it possible to make the rectangle instead of the mouse, change its size with mousewheel and confirm with mouse click?

import cv2
import numpy as np

cropping = False

x_start, y_start, x_end, y_end = 0, 0, 0, 0

image = cv2.imread('example.jpg')
oriImage = image.copy()


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)

cv2.namedWindow("image")
cv2.setMouseCallback("image", mouse_crop)

while True:

    i = image.copy()

    if not cropping:
        cv2.imshow("image", image)

    elif cropping:
        cv2.rectangle(i, (x_start, y_start), (x_end, y_end), (255, 0, 0), 2)
        cv2.imshow("image", i)

    cv2.waitKey(1)

# close all open windows
cv2.destroyAllWindows()

Answer 1

This is the basic structure you could use to do this. Create an initial rectangle on first click, resize the rectangle by scrolling up or down, then finalize the cropping by clicking again. You would need to add some checks to limit the rectangle when it goes out of the image bounds and when it goes "smaller than zero".

# if the left mouse button was released
if event == cv2.EVENT_LBUTTONUP:
    # create rectangle
    if not cropping:
        x_start, y_start = x-20, y-20
        x_end, y_end = x+20, y+20
        cropping = True # cropping is finished
    # finish cropping
    else:
        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)

elif event == cv2.EVENT_MOUSEWHEEL:
    print(flags)
    # scroll up
    if flags > 0:
        x_start, y_start = x_start-2, y_start-2
        x_end, y_end = x_end+2, y_end+2
    # scroll down
    else:
        x_start, y_start = x_start+2, y_start+2
        x_end, y_end = x_end-2, y_end-2

Answer 2

Thank you :) but i have still one problem my code looks now like this:

import cv2
import numpy as np

cropping = False

x_start, y_start, x_end, y_end = 0, 0, 0, 0

image = cv2.imread('example.jpg')
oriImage = image.copy()


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_MOUSEMOVE:
        x_start, y_start, x_end, y_end = x, y, x+96, y+96
        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)

    elif event == cv2.EVENT_MOUSEWHEEL:
        print(flags)
        # scroll up
        if flags > 0:
            x_start, y_start = x_start-15, y_start-15
            x_end, y_end = x_end+15, y_end+15
        # scroll down
        else:
            x_start, y_start = x_start+15, y_start+15
            x_end, y_end = x_end-15, y_end-15

cv2.namedWindow("image")
cv2.setMouseCallback("image", mouse_crop)

while True:

    i = image.copy()

    if not cropping:
        cv2.imshow("image", image)

    elif cropping:
        cv2.rectangle(i, (x_start, y_start), (x_end, y_end), (255, 0, 0), 2)
        cv2.imshow("image", i)

    cv2.waitKey(1)

# close all open windows
cv2.destroyAllWindows()

my problem is: the rectangle follows my mouse, I can make it bigger and smaller with the mousewheel but if I made it bigger and the mouse moves, it gets small again