Color Detector using Python and OpenCV

Here’s how you can make a color detector using Python and OpenCV :

1. Import all necessary libraries

    import numpy as np
    import cv2
    from PIL import Image
   

2. Select a color for detection

   • For this project, we are detecting yellow color (yellow = [0,255,255])

3. Calculate the range of colors on the hue palette

    def get_limits(color) :
        c = np.uint8([[color]])
        hsvC = cv2.cvtColor(c, cv2.COLOR_BGR2HSV)
        lowerLimit = hsvC[0][0][0] - 10, 100, 100
        upperLimit = hsvC[0][0][0] + 10, 255, 255
   
        lowerLimit = np.array(lowerLimit, dtype=np.uint8)
        upperLimit = np.array(upperLimit, dtype=np.uint8)
   
        return lowerLimit, upperLimit
   

   This function returns two values, the lowerLimit and upperLimit from the color palette, i.e. the range of the color.

Creating the structure of the project

yellow = [0, 255, 255]
cap = cv2.VideoCapture(0)
while True:
    ret, frame = cap.read()

    hsvImage = cv2.cvtColor(frame, cv2.COLOR_BGR2HSV)
    lowerLimit, upperLimit = get_limits(color=yellow)
    mask = cv2.inRange(hsvImage, lowerLimit, upperLimit)
    mask_ = Image.fromarray(mask)

    box = mask_.getbbox()

    if box is not None:
        x1, y1, x2, y2 = box
        frame = cv2.rectangle(frame, (x1, y1), (x2, y2), (0,255,0), 2)

    cv2.imshow('frame', frame)
    if cv2.waitKey(1) & 0xFF == ord('q'):
        break

cap.release()
cv2.destroyAllWindows()

This code generates a window with real-time camera input and detects the specified color in real-time.

---

Complete code for the project :

import numpy as np
import cv2
from PIL import Image

def get_limits(color) :
    c = np.uint8([[color]])
    hsvC = cv2.cvtColor(c, cv2.COLOR_BGR2HSV)
    lowerLimit = hsvC[0][0][0] - 10, 100, 100
    upperLimit = hsvC[0][0][0] + 10, 255, 255

    lowerLimit = np.array(lowerLimit, dtype=np.uint8)
    upperLimit = np.array(upperLimit, dtype=np.uint8)

    return lowerLimit, upperLimit


yellow = [0, 255, 255]
cap = cv2.VideoCapture(0)
while True:
    ret, frame = cap.read()

    hsvImage = cv2.cvtColor(frame, cv2.COLOR_BGR2HSV)
    lowerLimit, upperLimit = get_limits(color=yellow)
    mask = cv2.inRange(hsvImage, lowerLimit, upperLimit)
    mask_ = Image.fromarray(mask)

    box = mask_.getbbox()

    if box is not None:
        x1, y1, x2, y2 = box
        frame = cv2.rectangle(frame, (x1, y1), (x2, y2), (0,255,0), 2)

    cv2.imshow('frame', frame)
    if cv2.waitKey(1) & 0xFF == ord('q'):
        break

cap.release()
cv2.destroyAllWindows()

Peace ✌️