python opencv 笔记

保存图像：函数 cv2.imwrite() ，需要一个文件名，之后才是你要保存的图像

cv2.imwrite('messigray.png'，img)

使用OpenCV 处理鼠标事件：

查看所有被支持的鼠标事件：

import cv2
events=[i for i in dir(cv2) if 'EVENT'in i]
print event

结果如下：

[‘EVENT_FLAG_ALTKEY’, ‘EVENT_FLAG_CTRLKEY’, ‘EVENT_FLAG_LBUTTON’, ‘EVENT_FLAG_MBUTTON’, ‘EVENT_FLAG_RBUTTON’, ‘EVENT_FLAG_SHIFTKEY’, ‘EVENT_LBUTTONDBLCLK’, ‘EVENT_LBUTTONDOWN’, ‘EVENT_LBUTTONUP’, ‘EVENT_MBUTTONDBLCLK’, ‘EVENT_MBUTTONDOWN’, ‘EVENT_MBUTTONUP’, ‘EVENT_MOUSEMOVE’, ‘EVENT_RBUTTONDBLCLK’, ‘EVENT_RBUTTONDOWN’, ‘EVENT_RBUTTONUP’]

函数：cv2.setMouseCallback( )

实例1：创建一个简单的程序，他会在图片上你双击过的位置绘制一个圆圈

import numpy as np
import cv2

img = np.zeros((512,512,3),np.uint8)
def draw_circle(event,x,y,flags,param):
if event == cv2.EVENT_LBUTTONDOWN:
cv2.circle(img,(x,y),12,(255,0,0),-1)    #在鼠标点击处作一个圆
#cv2.line(img,(0,0),(x,y),(255,0,0),2)
cv2.imshow('image',img)
print "ok",x,y    #输出鼠标的坐标值

cv2.namedWindow('image')
cv2.setMouseCallback('image',draw_circle)
while (1):
cv2.imshow('image',img)
if cv2.waitKey(0):
break
cv2.destroyAllWindows()

实例2：

import numpy as np
import cv2

img = np.zeros((512,512,3),np.uint8)
drawing = False    #记录是否画画的状态
mode = True    #作图的模式：画矩形（True）或圆(False)
ix,iy = -1,-1    #记录鼠标的坐标

def draw_circle(event,x,y,flags,param):
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),(0,255,0),-1)
cv2.imshow('image',img)
print flags
else:
cv2.circle(img,(x,y),3,(0,0,255),-1)
cv2.imshow('image',img)
elif event == cv2.EVENT_LBUTTONUP:
drawing == False
if mode == True:
cv2.rectangle(img,(ix,iy),(x,y),(0,255,0),-1)
else:
cv2.circle(img,(x,y),5,(0,0,255),-1)

def do( ):
global mode
cv2.namedWindow('image')
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

do()

用滑动条做调色板：

函数：cv2.getTrackbarPos()， cv2.creatTrackbar()等

cv2.getTrackbarPos() 函数的一个参数是滑动条的名字，第二个参数是滑动条被放置窗口的名字，第三个参数是滑动条的默认位置。第四个参数是滑动条的最大值，第五个函数是回调函数，每次滑动条的滑动都会调用回调函数。回调函数通常都会含有一个默认参数，就是滑动条的位置。

实例：

import numpy as np
import cv2

def nothing(x):
pass

img = np.zeros((300,512,3),np.uint8)
cv2.namedWindow('image')

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

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

r=cv2.getTrackbarPos('R','image')
g=cv2.getTrackbarPos('G','image')
b=cv2.getTrackbarPos('B','image')
s=cv2.getTrackbarPos(switch,'image')

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

cv2.destroyAllWindows()