Python下使用Trackbar实现绘图板

import cv2
import numpy as np

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

def nothing(x):
 pass

def draw_circle(event,x,y,flags,param):
 r = cv2.getTrackbarPos('R','image')
 g = cv2.getTrackbarPos('G','image')
 b = cv2.getTrackbarPos('B','image')
 color = (b,g,r)
 s = cv2.getTrackbarPos('eraser','image')
 if s == 1:
 color = (255,255,255)
 thin = cv2.getTrackbarPos('thin','image')

 global ix,iy,drawing,mode
 if event == cv2.EVENT_LBUTTONDOWN:
 drawing = True
 ix,iy = x,y
 elif event == cv2.EVENT_MOUSEMOVE and flags == cv2.EVENT_FLAG_LBUTTON:
 if drawing == True:
 if mode == True:
 cv2.rectangle(img, (ix,iy),(x,y),color,-1)
 else:
 cv2.circle(img,(x,y),thin,color,-1)
 elif event == cv2.EVENT_LBUTTONUP:
 drawing == False

img = np.zeros((512,512,3), np.uint8)
img[:] = 255
cv2.namedWindow('image')
cv2.createTrackbar('R','image',0,255,nothing)
cv2.createTrackbar('G','image',0,255,nothing)
cv2.createTrackbar('B','image',0,255,nothing)

cv2.createTrackbar('eraser','image',0,1,nothing)
cv2.createTrackbar('thin','image',1,50,nothing)

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