使用HSV（OpenCV，Python）无法使黄色消失

Question

我有以下图片：

我想做的是保留所有红色数字。

使用此代码..

import cv2
import numpy as np

def callback(x):
    pass

cap = cv2.VideoCapture(0)
cv2.namedWindow('image')

ilowH = 0
ihighH = 179
ilowS = 0
ihighS = 255
ilowV = 0
ihighV = 255

# create trackbars for color change
cv2.createTrackbar('lowH', 'image', ilowH, 179, callback)
cv2.createTrackbar('highH', 'image', ihighH, 179, callback)

cv2.createTrackbar('lowS', 'image', ilowS, 255, callback)
cv2.createTrackbar('highS', 'image', ihighS, 255, callback)

cv2.createTrackbar('lowV', 'image', ilowV, 255, callback)
cv2.createTrackbar('highV', 'image', ihighV, 255, callback)

while True:
    # grab the frame
    frame = cv2.imread('color_test.png')

    # get trackbar positions
    ilowH = cv2.getTrackbarPos('lowH', 'image')
    ihighH = cv2.getTrackbarPos('highH', 'image')
    ilowS = cv2.getTrackbarPos('lowS', 'image')
    ihighS = cv2.getTrackbarPos('highS', 'image')
    ilowV = cv2.getTrackbarPos('lowV', 'image')
    ihighV = cv2.getTrackbarPos('highV', 'image')

    hsv = cv2.cvtColor(frame, cv2.COLOR_BGR2HSV)
    lower_hsv = np.array([ilowH, ilowS, ilowV])
    higher_hsv = np.array([ihighH, ihighS, ihighV])
    mask = cv2.inRange(hsv, lower_hsv, higher_hsv)

    frame = cv2.bitwise_and(frame, frame, mask=mask)

    # show thresholded image
    cv2.imshow('image', frame)
    k = cv2.waitKey(1) & 0xFF  # large wait time to remove freezing
    if k == 113 or k == 27:
        break

cv2.destroyAllWindows()
cap.release()

...我能获得的最大值是：

如何摆脱黄色并保留3个红色数字？ HSL是否适合在这种情况下使用？ 请记住，中心红色与其他2不同;一个是全红色（255,0,0），另一个是较少（237,28,36）RGB。