本文实例讲述了Python基于opencv实现的简单画板功能。分享给大家供大家参考，具体如下：

import cv2

import numpy as np

drawing = False # true if mouse is pressed

ix,iy = -1,-1

def nothing(x):

pass

# mouse callback function

def draw_circle(event,x,y,flags,param):

global ix,iy,drawing

g = param[0]

b = param[1]

r = param[2]

shape = param[3]

if event == cv2.EVENT_LBUTTONDOWN:

drawing = True

ix,iy = x,y

elif event == cv2.EVENT_MOUSEMOVE:

if drawing == True:

if shape == 0:

cv2.rectangle(img,(ix,iy),(x,y),(g,b,r),-1)

else:

cv2.circle(img,(x,y),5,(g,b,r),-1)

elif event == cv2.EVENT_LBUTTONUP:

drawing = False

if shape == 0:

cv2.rectangle(img,(ix,iy),(x,y),(g,b,r),-1)

else:

cv2.circle(img,(x,y),5,(g,b,r),-1)

# Create a black image, a window

img = np.zeros((300,512,3), np.uint8)

cv2.namedWindow('image')

# create trackbars for color change

cv2.createTrackbar('R','image',0,255,nothing)

cv2.createTrackbar('G','image',0,255,nothing)

cv2.createTrackbar('B','image',0,255,nothing)

# create switch for ON/OFF functionality

switch1 = '0 : OFF \n1 : ON'

switch2 = '0: Rectangle \n1: Line '

cv2.createTrackbar(switch1, 'image',0,1,nothing)

cv2.createTrackbar(switch2, 'image',0,1,nothing)

while(1):

cv2.imshow('image',img)

k = cv2.waitKey(1) & 0xFF

# get current positions of four trackbars

if k == 27:

break

r = cv2.getTrackbarPos('R','image')

g = cv2.getTrackbarPos('G','image')

b = cv2.getTrackbarPos('B','image')

shape = cv2.getTrackbarPos(switch2,'image')

s = cv2.getTrackbarPos(switch1,'image')

if s == 0:

img[:] = 0

else:

if k == 27:

break

cv2.setMouseCallback('image',draw_circle,(b,g,r,shape))

cv2.destroyAllWindows()

运行效果：

希望本文所述对大家Python程序设计有所帮助。