chapter7.py

import cv2
import numpy as np

#           Color detection

def empty(a):
    pass

cv2.namedWindow('TrackBars')    # creating new window
cv2.resizeWindow('TrackBars', 640, 240)     # sizing the newly created window

# Trackbars: can help us to play around with values in real time
cv2.createTrackbar('Hue min', 'TrackBars', 0, 179, empty)     # creating a trackbar. Hue value will be the name displayed in the trackbar, name of the window, min value, max value, function call on changing the value from trackbar
cv2.createTrackbar('Hue max', 'TrackBars', 179, 179, empty)
cv2.createTrackbar('Saturation min', 'TrackBars', 0, 255, empty)
cv2.createTrackbar('Saturation max', 'TrackBars', 255, 2255, empty)     # the range for saturation and value is 0-255
cv2.createTrackbar('Value min', 'TrackBars', 0, 255, empty)
cv2.createTrackbar('Value max', 'TrackBars', 255, 255, empty)

while True:
    img = cv2.imread('resources/lambo.png')
    imgHSV = cv2.cvtColor(img, cv2.COLOR_BGR2HSV)   # as such the range of HSV is 0-360 but its 0-179 in Open CV

    # getting all the six values from the track bars
    hueMin = cv2.getTrackbarPos('Hue min', 'TrackBars')
    hueMax = cv2.getTrackbarPos('Hue max', 'TrackBars')
    saturationMin = cv2.getTrackbarPos('Saturation min', 'TrackBars')
    saturationMax = cv2.getTrackbarPos('Saturation max', 'TrackBars')
    valueMin = cv2.getTrackbarPos('Value min', 'TrackBars')
    valueMax = cv2.getTrackbarPos('Value max', 'TrackBars')

    lower = np.array([hueMin, saturationMin, valueMin])
    upper = np.array([hueMax, saturationMax, valueMax])
    mask = cv2.inRange(imgHSV, lower, upper)    # this will give the filtered out image in range [lower upper]
    finalImg = cv2.bitwise_and(img, img, mask=mask)     # it will perform 'and' operation on pixels of original image and mask

    print(hueMin, hueMax, saturationMin, saturationMax, valueMin, valueMax)
    cv2.imshow('original', img)
    cv2.imshow('HSV', imgHSV)
    cv2.imshow('Mask', mask)
    cv2.imshow('final', finalImg)
    cv2.waitKey(1)