python-opencv实现绘制矩形roi区域

import cv2## 标题

global img
global point1, point2
def on_mouse(event, x, y, flags, param): #1.event是 CV_EVENT_*变量之一 2.x和y是鼠标指针在图像坐标系的坐标（不是窗口坐标系） 3.flags是CV_EVENT_FLAG的组合， param是用户定义的传递到setMouseCallback函数调用的参数
global img, point1, point2
img2 = img.copy()
if event == cv2.EVENT_LBUTTONDOWN: #左键点击
point1 = (x,y)
cv2.circle(img2, point1, 10, (0,255,0), 1)
cv2.imshow(‘image’, img2)
elif event == cv2.EVENT_MOUSEMOVE and (flags & cv2.EVENT_FLAG_LBUTTON): #按住左键拖曳
cv2.rectangle(img2, point1, (x,y), (255,0,0), 1) #鼠标移动和拖拽
cv2.imshow(‘image’, img2)
elif event == cv2.EVENT_LBUTTONUP: #左键释放
point2 = (x,y)
cv2.rectangle(img2, point1, point2, (0,0,255), 1)
cv2.imshow(‘image’, img2)
min_x = min(point1[0],point2[0])
min_y = min(point1[1],point2[1])
width = abs(point1[0] - point2[0])
height = abs(point1[1] -point2[1])
cut_img = img[min_y:min_y+height, min_x:min_x+width]
cv2.imwrite(‘lena3.jpg’, cut_img)
def main():
global img #global 看做全局变量
img = cv2.imread(‘Show_Image.jpg’)
cv2.namedWindow(‘image’)
cv2.setMouseCallback(‘image’, on_mouse)
cv2.imshow(‘image’, img)
cv2.waitKey(0)

if name == ‘main’: #if name == 'main’的意思是：当.py文件被直接运行时，if name == ‘main’之下的代码块将被运行；当.py文件以模块形式被导入时，if name == ‘main’之下的代码块不被运行。
main()
‘’‘EVENT define CV_EVENT_MOUSEMOVE 0 滑动
define CV_EVENT_LBUTTONDOWN 1 左键点击
define CV_EVENT_RBUTTONDOWN 2 右键点击
define CV_EVENT_MBUTTONDOWN 3 中间点击
define CV_EVENT_LBUTTONUP 4 左键释放
define CV_EVENT_RBUTTONUP 5 右键释放
define CV_EVENT_MBUTTONUP 6 中间释放
define CV_EVENT_LBUTTONDBLCLK 7 左键双击
define CV_EVENT_RBUTTONDBLCLK 8 右键双击
define CV_EVENT_MBUTTONDBLCLK 9 中间释放
flags
define CV_EVENT_FLAG_LBUTTON 1 左键拖拽
define CV_EVENT_FLAG_RBUTTON 2 右键拖拽
define CV_EVENT_FLAG_MBUTTON 4 中间拖拽
define CV_EVENT_FLAG_CTRLKEY 8 (8~15)按Ctrl不放事件
define CV_EVENT_FLAG_SHIFTKEY 16 (16~31)按Shift不放事件
define CV_EVENT_FLAG_ALTKEY 32 (32~39)按Alt不放事件（后面8-39还有待研究）’’’