OpenCV is an open-source image recognition library.
INSTALLATION PYTHON 3.X
Open Terminal/Command Prompt and type :
~ pip
install
opencv-python
GETTING STARTED (HOW TO READ IMAGES)
1.Open PyCharm.
imread
()
function.
waitkey
()
function.
1
import cv2
# LOAD AN IMAGE USING 'IMREAD'
img = cv2 .imread("Resources/lena.png")
# DISPLAY
cv2 .imshow("Lena Soderberg”, img)
cv2. waitKey(0)
PLAYING VIDEO USING VideoCapture() FUNCTION
Open PyCharm.
Import cv2.
Paste a test video in the directory.
Create variable to store video using VideoCapture() function.
Create an infinite while loop to display each frame of the video continuously.
Display the video using imshow() function.
Add a delay using a waitkey() function.
1
import cv2
frameWidth = 640
frameHeight = 480
cap = cv2.VideoCapture("Resources/test_ video.mp4" )
while True:
success, img = cap.read()
img = cv2.resize(img, (frameWidth, frameHeight))
cv2.imshow("Result" , img)
break
ACCESSING LIVE FEED FROM WEBCAM
Open PyCharm.
Import cv2.
Create variable to store video using VideoCapture() function.
Pass parameter 0 in VideoCapture(0) to access webcam.
Create an infinite while loop to display each frame of the webcam’s video continuously.
Display the live feed using imshow() function.
Add a delay of infinity using waitKey(0).
1
import cv2
Width = 640
Height = 480
cap = cv2.VideoCapture(0)
cap .set (3, frameWidth)
cap .set (4, frameHeight)
cap .set (10, 150)
while True:
success, img = cap .read ()
cv2.imshow("Result" , img)
break
FUNCTIONS OF OPENCV
Converting image to grayscale
Open PyCharm.
Import cv2.
Create variable to store image using
imread
()
function.
To convert to grayscale use
cv2
.cvtColor
()
function
Pass the parameter image location and
COLOR_BGR2GRAY
to convert.
1
import cv2
img = cv2.imread("Resources/lena.png" )
imgGray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)
cv2.imshow("Gray Image" , imgGray)
cv2.waitKey(0)
Edge detection
Open PyCharm.
Import cv2.
Create variable to store image using
imread
()
function.
To detect edge use
cv2
.Canny
()
function
Pass the parameter image location and threshold to convert.
1
import cv2
img = cv2.imread("Resources/lena.png" )
imgCanny = cv2.Canny(img, 150, 200)
cv2.imshow("Canny Image”, imgCanny)
cv2.waitKey(0)
CROPPING IMAGE
Import numpy and cv2.
Create two variables to store the height and width of the image.
Create two numpy arrays to store the coordinates.
First array - store the coordinates of the image to be cropped.
Second array - store the coordinates of the complete image.
Crop the image using getPerspective() and wrapPerspective() function.
1
image = cv2.imread("Assets/cards.jpg" )
width, height = 250 , 350
point1 = np.float32([[111 , 219 ], [287 , 188 ], [154 , 482 ], [352 , 440 ]])
point2 = np.float32([[0 , 0 ], [width, 0 ], [0 , height], [width, height]])
matrix = cv2.getPerspectiveTransform(point1, point2)
Output = cv2.warpPerspective(image, matrix, (width, height))
cv2.imshow("Image”, image)
cv2.imshow(" Output”, Output)
cv2.waitKey(0 )
FACE DETECTION
Open PyCharm.
Import cv2.
Convert image to greyscale using
cv2
.cvtColor
()
function.
Detect face using
detectMultiscale
()
function.
Draw a rectangle around the detected face.
1
import cv2
face_Cascade = cv2.CascadeClassifier("Resources/haarcascade_frontalface_default.xml" )
image = cv2.imread('Resources/lena.png' )
imgGray = cv2.cvtColor(image, cv2.COLOR_BGR2GRAY)
faces = face_Cascade.detectMultiScale(imgGray, 1.1 , 4 )
for (x, y, w, h) in faces:
cv2.rectangle(image, (x, y), (x + w, y + h), (255 , 0 , 0 ), 2 )
cv2.imshow("Result" , image)
cv2.waitKey(0 )
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