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diff --git a/opencv.html.markdown b/opencv.html.markdown new file mode 100644 index 00000000..f8763b35 --- /dev/null +++ b/opencv.html.markdown @@ -0,0 +1,144 @@ +--- +category: tool +tool: OpenCV +filename: learnopencv.py +contributors: + - ["Yogesh Ojha", "http://github.com/yogeshojha"] +--- +### Opencv + +OpenCV (Open Source Computer Vision) is a library of programming functions mainly aimed at real-time computer vision. +Originally developed by Intel, it was later supported by Willow Garage then Itseez (which was later acquired by Intel). +Opencv currently supports wide variety of languages like, C++, Python, Java etc + +#### Installation +Please refer to these articles for installation of OpenCV on your computer. + +* Windows Installation Instructions: [https://opencv-python-tutroals.readthedocs.io/en/latest/py_tutorials/py_setup/py_setup_in_windows/py_setup_in_windows.html#install-opencv-python-in-windows]() +* Mac Installation Instructions (High Sierra): [https://medium.com/@nuwanprabhath/installing-opencv-in-macos-high-sierra-for-python-3-89c79f0a246a]() +* Linux Installation Instructions (Ubuntu 18.04): [https://www.pyimagesearch.com/2018/05/28/ubuntu-18-04-how-to-install-opencv]() + +### Here we will be focusing on python implementation of OpenCV + +```python +# Reading image in OpenCV +import cv2 +img = cv2.imread('cat.jpg') + +# Displaying the image +# imshow() function is used to display the image +cv2.imshow('Image',img) +# Your first arguement is the title of the window and second parameter is image +# If you are getting error, Object Type None, your image path may be wrong. Please recheck the pack to the image +cv2.waitKey(0) +# waitKey() is a keyboard binding function and takes arguement in milliseconds. For GUI events you MUST use waitKey() function. + +# Writing an image +cv2.imwrite('catgray.png',img) +# first arguement is the file name and second is the image + +# Convert image to grayscale +gray_image = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY) + +# Capturing Video from Webcam +cap = cv2.VideoCapture(0) +#0 is your camera, if you have multiple camera, you need to enter their id +while(True): + # Capturing frame-by-frame + _, frame = cap.read() + cv2.imshow('Frame',frame) + # When user presses q -> quit + if cv2.waitKey(1) & 0xFF == ord('q'): + break +# Camera must be released +cap.release() + +# Playing Video from file +cap = cv2.VideoCapture('movie.mp4') +while(cap.isOpened()): + _, frame = cap.read() + # Play the video in grayscale + gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY) + cv2.imshow('frame',gray) + if cv2.waitKey(1) & 0xFF == ord('q'): + break +cap.release() + +# Drawing The Line in OpenCV +# cv2.line(img,(x,y),(x1,y1),(color->r,g,b->0 to 255),thickness) +cv2.line(img,(0,0),(511,511),(255,0,0),5) + +# Drawing Rectangle +# cv2.rectangle(img,(x,y),(x1,y1),(color->r,g,b->0 to 255),thickness) +# thickness = -1 used for filling the rectangle +cv2.rectangle(img,(384,0),(510,128),(0,255,0),3) + +# Drawing Circle +cv2.circle(img,(xCenter,yCenter), radius, (color->r,g,b->0 to 255), thickness) +cv2.circle(img,(200,90), 100, (0,0,255), -1) + +# Drawing Ellipse +cv2.ellipse(img,(256,256),(100,50),0,0,180,255,-1) + +# Adding Text On Images +cv2.putText(img,"Hello World!!!", (x,y), cv2.FONT_HERSHEY_SIMPLEX, 2, 255) + +# Blending Images +img1 = cv2.imread('cat.png') +img2 = cv2.imread('openCV.jpg') +dst = cv2.addWeighted(img1,0.5,img2,0.5,0) + +# Thresholding image +# Binary Thresholding +_,thresImg = cv2.threshold(img,127,255,cv2.THRESH_BINARY) +# Adaptive Thresholding +adapThres = cv2.adaptiveThreshold(img,255,cv2.ADAPTIVE_THRESH_GAUSSIAN_C, cv2.THRESH_BINARY,11,2) + +# Blur Image +# Gaussian Blur +blur = cv2.GaussianBlur(img,(5,5),0) +# Median Blur +medianBlur = cv2.medianBlur(img,5) + +# Canny Edge Detection +img = cv2.imread('cat.jpg',0) +edges = cv2.Canny(img,100,200) + +# Face Detection using Haar Cascades +# Download Haar Cascades from https://github.com/opencv/opencv/blob/master/data/haarcascades/ +import cv2 +import numpy as np +face_cascade = cv2.CascadeClassifier('haarcascade_frontalface_default.xml') +eye_cascade = cv2.CascadeClassifier('haarcascade_eye.xml') + +img = cv2.imread('human.jpg') +gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY) + +aces = face_cascade.detectMultiScale(gray, 1.3, 5) +for (x,y,w,h) in faces: + cv2.rectangle(img,(x,y),(x+w,y+h),(255,0,0),2) + roi_gray = gray[y:y+h, x:x+w] + roi_color = img[y:y+h, x:x+w] + eyes = eye_cascade.detectMultiScale(roi_gray) + for (ex,ey,ew,eh) in eyes: + cv2.rectangle(roi_color,(ex,ey),(ex+ew,ey+eh),(0,255,0),2) + +cv2.imshow('img',img) +cv2.waitKey(0) + +cv2.destroyAllWindows() +# destroyAllWindows() destroys all windows. +# If you wish to destroy specific window pass the exact name of window you created. +``` + +### Further Reading: + +* Download Cascade from [https://github.com/opencv/opencv/blob/master/data/haarcascades]() +* OpenCV drawing Functions [https://docs.opencv.org/2.4/modules/core/doc/drawing_functions.html]() +* An up-to-date language reference can be found at [https://opencv.org]() +* Additional resources may be found at [https://en.wikipedia.org/wiki/OpenCV]() +* Good OpenCv Tutorials + * [https://opencv-python-tutroals.readthedocs.io/en/latest/py_tutorials/py_tutorials.html]() + * [https://realpython.com/python-opencv-color-spaces]() + * [https://pyimagesearch.com]() + * [https://www.learnopencv.com]() |