opencv画图练习：目前只做到矩形之间会有覆盖，矩形只能越画越大，颜色，宽度可调

import cv2 as cv
import numpy as np
img = np.zeros((512,512,3),np.uint8)
cv.namedWindow('image')

def nothing(x):
    pass

cv.createTrackbar('R','image',0,255,nothing)
cv.createTrackbar('G','image',0,255,nothing)
cv.createTrackbar('B','image',0,255,nothing)
cv.createTrackbar('width','image',1,50,nothing)



drawing = False
mode = True
ix,iy=-1,-1
def draw_circle(event,x,y,flags,param):
    global ix,iy,drawing,mode,width,b,g,r
    if event == cv.EVENT_LBUTTONDOWN:
        drawing = True
        ix,iy = x,y
    elif event == cv.EVENT_MOUSEMOVE:
        if drawing:
            cv.rectangle(img,(ix,iy),(x,y),(b,g,r),-1)
            cv.rectangle(img,(ix+width,iy+width),(x-width,y-width),(0,0,0),-1)#画出未填充矩形
        #else:
            #cv.circle(img,(x,y),5,(0,0,255),-1)#追踪鼠标移动生成点
    elif event == cv.EVENT_LBUTTONUP:
        drawing = False
        if mode:
            cv.rectangle(img,(ix,iy),(x,y),(b,g,r),1)
        else:
            cv.circle(img,(x,y),5,(b,g,r),-1)
cv.setMouseCallback('image', draw_circle)
while 1:
    cv.imshow('image',img)
    k = cv.waitKey(1) & 0xFF
    if k == 27:
        break
    r = cv.getTrackbarPos('R', 'image')
    g = cv.getTrackbarPos('G', 'image')
    b = cv.getTrackbarPos('B', 'image')
    width = cv.getTrackbarPos('width', 'image')

cv.destroyAllWindows()