如何在 RGB 颜色检测中使用“if 条件”？

Question

I am new to OpenCV and python. I am trying to detect colors in real-time using a camera. I want to put an "if condition" when the detected color is Red, Green or Blue. If it detects red then it should print "The color is RED" The same is the case I want to apply with the Green and Blue color. Here is the code that is showing RGB colors separately. Is there anyone who can help me out with this? Thanks in advance:)

import cv2
import numpy as np
import matplotlib.pyplot as plt

cap = cv2.VideoCapture(0)

while True:
    _, frame = cap.read()
    hsv_frame = cv2.cvtColor(frame, cv2.COLOR_BGR2HSV)

    # Red color
    low_red = np.array([161, 155, 84])
    high_red = np.array([179, 255, 255])
    red_mask = cv2.inRange(hsv_frame, low_red, high_red)
    red = cv2.bitwise_and(frame, frame, mask=red_mask)


    # Blue color
    low_blue = np.array([94, 80, 2])
    high_blue = np.array([126, 255, 255])
    blue_mask = cv2.inRange(hsv_frame, low_blue, high_blue)
    blue = cv2.bitwise_and(frame, frame, mask=blue_mask)

    # Green color
    low_green = np.array([25, 52, 72])
    high_green = np.array([102, 255, 255])
    green_mask = cv2.inRange(hsv_frame, low_green, high_green)
    green = cv2.bitwise_and(frame, frame, mask=green_mask)

    # Every color except white
    low = np.array([0, 42, 0])
    high = np.array([179, 255, 255])
    mask = cv2.inRange(hsv_frame, low, high)
    result = cv2.bitwise_and(frame, frame, mask=mask)

#   plt.imshow(mask,cmap='gray')

######## Chech if the shown object has red color or not ##########

    img_height, img_width, _=hsv_frame.shape
    for i in range(img_height):
        for j in range(img_width):
            if hsv_frame[i][j][1]>= low_red and hsv_frame[i][j][1]<=upper_red:
                print("Red found")

#     cv2.imshow("Red", red)
#     cv2.imshow("Blue", blue)
#     cv2.imshow("Green", green)

    if cv2.waitKey(1)==13:
        break

cap.release()
cv2.waitKey(1)
cv2.destroyAllWindows()

The error im getting is

---> 40 if hsv_frame[i][j][1]>= low_red and hsv_frame[i][j][1]<=upper_red: ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all()

Answer 1

The line

if hsv_frame[i][j][1]>= low_red and hsv_frame[i][j][1]<=upper_red:

compares two arrays, ie pixels (r,g,b) <= (r,g,b) which will return 3 values. ie (True/False, True/False, True/False).

So you need to use either,

any() (atleast 1 is true)

or

all() (all must be true)

considering its pixel comparision i would recommend you to use all,

replace it with the below code.

if (hsv_frame[i][j][1]>= low_red).all() and (hsv_frame[i][j][1]<=upper_red).all():

Answer 2

Looks like you want to count if the image has red color or not, where red is defined by your low_red and high_red bounds.

You already have the mask with the red region, why not use that?

countRed = cv2.countNonZero(red_mask)
if countRed > 0: #choose whatever condition you want
    print("Red found")