OpenCV- image processing - the color space conversion (tracking object)

• Color space conversion

  ---

　　Common conversion method: the BGR <-> the RGB , the BGR <-> Gray and the BGR <-> the HSV

　　Function: cv2.cvtColor (input_image , flag) , wherein the flag is a conversion type.

　　Code:

. 1  Import CV2
 2  Import numpy AS NP
 . 3  
. 4 IMG = cv2.imread ( ' ../image/min.jpg ' )
 . 5  
. 6  # the BGR converted to RGB matrix 
. 7 IMG = cv2.cvtColor (IMG, cv2.COLOR_BGR2RGB)
 . 8  
. 9  # the BGR GRAY converted into matrix 
10 IMG = cv2.cvtColor (IMG, cv2.COLOR_BGR2GRAY)
 . 11  
12 is  # the BGR converted into HSV matrix 
13 is IMG = cv2.cvtColor (IMG, cv2.COLOR_BGR2HSV)

View Code

　　Note: In OpenCV the HSV format, H (color / chromaticity) is in the range [0 , 179] , S range (saturation) of [0 , 255] , V (brightness) ranges [0 , 255] . But the software uses different values may be different. The general ranges: H 0 to 360 °, S 0 to 100%, V is 0 to 255.

 

• Simple object tracking

　　Using the image in the HSV mode, the extraction of a particular color object (HSV color space represents a particular color more easily than the BGR color space)

　　

. 1  Import numpy AS NP
 2  Import CV2
 . 3  
. 4  # capture camera 
. 5 CAP = cv2.VideoCapture (0)
 . 6  
. 7  the while (. 1 ):
 . 8  
. 9      # acquires each frame 
10      RET, Frame = cap.read ()
 . 11  
12 is      # conversion to HSV space 
13 is      HSV = cv2.cvtColor (Frame, cv2.COLOR_BGR2HSV)
 14  
15      # set threshold blue 
16      lower_blue np.array = ([110, 50, 50 ])
 . 17      upper_blue np.array = ([130., 255, 255 ])
 18 
19      # Construction mask according to the threshold value (within the threshold value is set to 255 pixels, otherwise 0) 
20 is      mask = cv2.inRange (HSV, lower_blue, upper_blue)
 21 is  
22 is      RES = cv2.bitwise_and (Frame, Frame, mask = mask)
 23 is  
24      cv2.imshow ( ' Frame ' , Frame)
 25      cv2.imshow ( ' mask ' , mask)
 26 is      cv2.imshow ( ' RES ' , RES)
 27      K = cv2.waitKey (. 5) & 0xFF
 28      IF K == 27 :
 29          BREAK 
30  
31 cv2.destroyAllWindows ()