python - 在 OpenCV 中使用 createTrackbar() 方法制作绘画应用程序时，EVENT_MOUSEMOVE 不起作用？

Question

我一直在尝试使用 OpenCV 和 Python 制作一个简单的 Paint 应用程序。

这里我使用了 trackbar 方法创建了五个 adjustable fields(三个 (R, G, B) fields，一个 On/Off switch 来启用或不启用绘图，一个 field 来绘制一圈可调半径)。

目前，正在读取所有字段数据并将其提供给适当的函数。我希望我的画图应用程序具有可调节的背景颜色，并在鼠标悬停的任何地方制作圆圈，半径和颜色均可调节。

但是当鼠标悬停在图像上时，我的代码没有画一个圆圈。

import cv2
import numpy as np
def nothing(x):
    pass

colo = (0,0,255)
radius = 5

def draw_circle(event,x,y,flags,param):
    global colo,radius
    if event == cv2.EVENT_MOUSEMOVE:
        # print(str(colo) + " " + str(radius))
        cv2.circle(img,(x,y),radius,colo,-1)    

# Create a black image, a window
img = np.zeros((300,512,3), np.uint8)
cv2.namedWindow('image')
cv2.setMouseCallback('image',draw_circle)   

# create trackbars for color and radius change
cv2.createTrackbar('Red','image',0,255,nothing)
cv2.createTrackbar('Green','image',0,255,nothing)
cv2.createTrackbar('Blue','image',0,255,nothing)
cv2.createTrackbar('CirRadius','image',5,50,nothing)

# create switch for ON/OFF functionality
switch = '0 : OFF \n1 : ON'
cv2.createTrackbar(switch, 'image',0,1,nothing)

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

    # get current positions of five trackbars
    r = cv2.getTrackbarPos('Red','image')
    g = cv2.getTrackbarPos('Green','image')
    b = cv2.getTrackbarPos('Blue','image')
    s = cv2.getTrackbarPos(switch,'image')
    radius = cv2.getTrackbarPos('CirRadius','image')
    colo = (b,g,r)

    if s == 0:
        img[:] = 0
    else:
        img[:] = [b,g,r]
cv2.destroyAllWindows()

Answer 1

如果圆圈和背景的颜色保持不变，我们无法区分或定位圆圈。由于您使用的是 global colo，因此它不可见。

import cv2
import numpy as np
def nothing(x):
    pass

colo = (0,0,255)
radius = 5

def draw_circle(event,x,y,flags,param):
    global colo,radius
    if event == cv2.EVENT_MOUSEMOVE:
        # print(str(colo) + " " + str(radius))
        cv2.circle(img,(x,y),radius,(0,0,255),-1)    

# Create a black image, a window
img = np.zeros((300,512,3), np.uint8)
cv2.namedWindow('image')
cv2.setMouseCallback('image',draw_circle)   

# create trackbars for color and radius change
cv2.createTrackbar('Red','image',0,255,nothing)
cv2.createTrackbar('Green','image',0,255,nothing)
cv2.createTrackbar('Blue','image',0,255,nothing)
cv2.createTrackbar('CirRadius','image',5,50,nothing)

# create switch for ON/OFF functionality
switch = '0 : OFF \n1 : ON'
cv2.createTrackbar(switch, 'image',0,1,nothing)

while(1):
    cv2.imshow('image',img)
    # get current positions of five trackbars
    r = cv2.getTrackbarPos('Red','image')
    g = cv2.getTrackbarPos('Green','image')
    b = cv2.getTrackbarPos('Blue','image')
    s = cv2.getTrackbarPos(switch,'image')
    radius = cv2.getTrackbarPos('CirRadius','image')
    colo = (b,g,r)

    if s == 0:
        img[:] = 0
    else:
        img[:] = [b,g,r]

    k = cv2.waitKey(1) & 0xFF
    if k == 27:
        break


cv2.destroyAllWindows()