python-3.x - 在 openCV python 中绘制矩形

Question

我正在尝试在 python 中使用鼠标作为 Opencv 输入来绘制矩形。我从 opencv 文档中制作了这段代码。绘制矩形时出现问题，即当您尝试从起点拖动矩形时一直绘制到终点。就像我在图片中展示的那样。

如何绘制干净的未填充矩形？在那里我可以看到绘制一个实际的矩形。就像我们在 Paint 中所做的那样

import cv2
import numpy as np

drawing = False 
ix,iy = -1,-1

def draw_rect(event,x,y,flags,param):
global ix,iy,drawing,mode

if event == cv2.EVENT_LBUTTONDOWN:
    drawing = True
    ix,iy = x,y

elif event == cv2.EVENT_MOUSEMOVE:
    if drawing == True:
            cv2.rectangle(img,(ix,iy),(x,y),(0,255,0),1)


elif event == cv2.EVENT_LBUTTONUP:
    drawing = False
    cv2.rectangle(img,(ix,iy),(x,y),(0,255,0),1)



img = np.zeros((512,512,3), np.uint8)
cv2.namedWindow('image')
cv2.setMouseCallback('image',draw_rect)

while(1):
cv2.imshow('image',img)
k = cv2.waitKey(1) & 0xFF
if k == 27:
    break

cv2.destroyAllWindows()

谁能告诉我为什么会这样？有什么解决办法吗？？

Answer 1

当你在 event == cv2.EVENT_MOUSEMOVE 期间移动鼠标时，你也会同时绘制 recatngle cv2.rectangle(img,(ix,iy),(x,y ),(0,255,0),1)。

尝试下面的一段代码。

import cv2
import numpy as np

drawing = False # true if mouse is pressed
mode = True # if True, draw rectangle.
ix,iy = -1,-1

# mouse callback function
def draw_circle(event,x,y,flags,param):
  global ix,iy,drawing,mode

  if event == cv2.EVENT_LBUTTONDOWN:
      drawing = True
      ix,iy = x,y

  elif event == cv2.EVENT_MOUSEMOVE:
    if drawing == True:
        if mode == True:
            cv2.rectangle(img,(ix,iy),(x,y),(0,255,0),3)
            a=x
            b=y
            if a != x | b != y:
                 cv2.rectangle(img,(ix,iy),(x,y),(0,0,0),-1)
        else:
            cv2.circle(img,(x,y),5,(0,0,255),-1)

  elif event == cv2.EVENT_LBUTTONUP:
    drawing = False
    if mode == True:
        cv2.rectangle(img,(ix,iy),(x,y),(0,255,0),2)

    else:
        cv2.circle(img,(x,y),5,(0,0,255),-1)

img = np.zeros((512,512,3), np.uint8)
cv2.namedWindow('image')
cv2.setMouseCallback('image',draw_circle)

while(1):
 cv2.imshow('image',img)
 k = cv2.waitKey(1) & 0xFF
 if k == ord('m'):
    mode = not mode
 elif k == 27:
    break

cv2.destroyAllWindows()   

希望它能解决您的问题。干杯。

预期输出:

更新

---

以上代码仅适用于黑色背景图像。但是我们可以为任何图像绘制矩形，所以 -

尝试下面的一段代码。

# import the necessary packages
import cv2
import argparse

# now let's initialize the list of reference point
ref_point = []

def shape_selection(event, x, y, flags, param):
    # grab references to the global variables
    global ref_point, crop

    # if the left mouse button was clicked, record the starting
    # (x, y) coordinates and indicate that cropping is being performed
    if event == cv2.EVENT_LBUTTONDOWN:
        ref_point = [(x, y)]

    # check to see if the left mouse button was released
    elif event == cv2.EVENT_LBUTTONUP:
        # record the ending (x, y) coordinates and indicate that
        # the cropping operation is finished
        ref_point.append((x, y))

        # draw a rectangle around the region of interest
        cv2.rectangle(image, ref_point[0], ref_point[1], (0, 255, 0), 2)
        cv2.imshow("image", image)


# construct the argument parser and parse the arguments
ap = argparse.ArgumentParser()
ap.add_argument("-i", "--image", required=True, help="Path to the image")
args = vars(ap.parse_args())

# load the image, clone it, and setup the mouse callback function
image = cv2.imread(args["image"])
clone = image.copy()
cv2.namedWindow("image")
cv2.setMouseCallback("image", shape_selection)


# keep looping until the 'q' key is pressed
while True:
    # display the image and wait for a keypress
    cv2.imshow("image", image)
    key = cv2.waitKey(1) & 0xFF

    # press 'r' to reset the window
    if key == ord("r"):
        image = clone.copy()

    # if the 'c' key is pressed, break from the loop
    elif key == ord("c"):
        break

# close all open windows
cv2.destroyAllWindows() 

将文件另存为 capture_events.py，为了进行测试，我们选择了位于同一目录中的演示图片。现在按照以下方式运行代码 -

python capture_events.py --image demo.jpg

预期输出:

如果出于某种原因我们想要重新选择图像的任何部分，我们可以简单地按“r”来摆脱错误的选择并尝试新的选择。

希望，它会帮助更多。检查这个gist ，您可以在此基础上实现更多功能。干杯。