• 目標(biāo)

1. 學(xué)習(xí) opencv的鼠標(biāo)事件和鼠標(biāo)事件回調(diào)函數(shù)cv2.setMouseCallback()的使用胰柑。
2. 根據(jù)獲取到的鼠標(biāo)的位置坐標(biāo)繪制不同的圖形。

• 示例代碼

• 查看opencv支持的鼠標(biāo)事件

python    
   
  # -*- coding:utf-8-*-     
 
  import numpy as np  
import cv2    
  
  events=[i for i in dir(cv2) if 'EVENT'in i]
print events

輸出結(jié)果

['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']

• 利用鼠標(biāo)事件，以圖片上雙擊的位置為中心妇斤，繪制一個(gè)圓

python    
     
  # -*- coding:utf-8-*-     
 
  import numpy as np  
import cv2    
              
  def draw_circle(event, x, y, flags, param):    
     if event == cv2.EVENT_LBUTTONDBLCLK:        
        cv2.circle(img, (x, y), 100, (255, 0, 0), -1)    
  
  # 新建圖像窗口并將窗口與回調(diào)函數(shù)綁定
img = np.zeros((512, 512, 3), np.uint8)
cv2.namedWindow('image')      
cv2.setMouseCallback('image', draw_circle)    
        
 while (1):     
# 顯示圖像并且按鍵盤上的**ESC**鍵即可關(guān)閉窗口  
    cv2.imshow('image', img)    
    if cv2.waitKey(20) & 0xFF == 27:       
        break    
# 最后銷毀窗口  
  cv2.destroyAllWindows()

顯示結(jié)果
以雙擊鼠標(biāo)的位置為圓心椎组，100px為半徑，畫出的圓如下

雙擊鼠標(biāo)后畫出的圓

• 利用鼠標(biāo)事件赶盔，拖動(dòng)鼠標(biāo)時(shí)繪制矩形或圓

python    

  # -*- coding:utf-8-*-    
  
  import numpy as np  
import cv2    
    
  # 默認(rèn)繪圖狀態(tài)不可用企锌，為False，當(dāng)鼠標(biāo)按下時(shí)值為True   
  drawing = False  
# mode為True時(shí)畫矩形招刨，值為False時(shí)畫圓  
  mode = True  
# 定義x1, y1兩個(gè)值
x1, y1 = -1, -1  
  
  # 創(chuàng)建回調(diào)函數(shù)    
def draw_circle(event, x, y, flags, param):    
    global ix, iy, drawing, mode    
    # 按下鼠標(biāo)左鍵時(shí)返回起始位置坐標(biāo)    
    if event == cv2.EVENT_LBUTTONDOWN:        
        drawing = True        
        x1,  y1 = x, y  
  
    # 當(dāng)鼠標(biāo)左鍵按下并移動(dòng)時(shí)繪制圖形
    elif event == cv2.EVENT_MOUSEMOVE and flags == cv2.EVENT_FLAG_LBUTTON:    
        if drawing == True:        
            if mode == True:  
                #  (x1, y1)為矩形起點(diǎn)霎俩，矩形顏色為(0, 255, 0)哀军，線條粗細(xì)為1px           
                cv2.rectangle(img, (x1, y1), (x, y), (0, 255, 0),1)            
            else:            
                # 起始點(diǎn)為圓心，起點(diǎn)到終點(diǎn)為半徑的圓
                r=int(np.sqrt((x-x1)**2+(y-y1)**2)) 
                cv2.circle(img,(x,y),r,(0,0,255),-1)  
    # 當(dāng)鼠標(biāo)松開停止繪畫  
    elif event==cv2.EVENT_LBUTTONUP:   
        drawing==False  
 
  # 新建圖像窗口并將窗口與回調(diào)函數(shù)綁定
  img=np.zeros((512,512,3),np.uint8) 
cv2.namedWindow('image') 
cv2.setMouseCallback('image',draw_circle)   

  while(1): 
      cv2.imshow('image',img) 
      k=cv2.waitKey(1)&0xFF  
      # 鍵盤輸入**m**時(shí)打却，畫圓 
      if k==ord('m'):
         mode=not mode 
      elif k==27: 
          break
cv2.destroyAllWindows()

顯示結(jié)果

矩形和圓

圓組成的線圈

可見在鼠標(biāo)拖動(dòng)過程中會(huì)不斷以起始點(diǎn)為圓心蹬叭，不斷畫圓。