Identifying the range of a color in HSV using openCV

Question

I am working on identifying the color yellow using openCV in python. I have come to this step where I have to define the lower and upper range of the color yellow in HSV.

Example for defining the range of Blue:

lower_blue = np.array([110,50,50])
upper_blue = np.array([130,255,255])

The HSV is usually defined in percentage, I want to know how to define the range for yellow like the example.

This is the colorspaces tutorial I've been following.

Edit: There are some suggestions in the blog mentioned above, but it does not give me the desired output.

Answer 1

You can use this sample color palette. First value is the upper limit and second value is the lower limit

color_dict_HSV = {'black': [[180, 255, 30], [0, 0, 0]],
              'white': [[180, 18, 255], [0, 0, 231]],
              'red1': [[180, 255, 255], [159, 50, 70]],
              'red2': [[9, 255, 255], [0, 50, 70]],
              'green': [[89, 255, 255], [36, 50, 70]],
              'blue': [[128, 255, 255], [90, 50, 70]],
              'yellow': [[35, 255, 255], [25, 50, 70]],
              'purple': [[158, 255, 255], [129, 50, 70]],
              'orange': [[24, 255, 255], [10, 50, 70]],
              'gray': [[180, 18, 230], [0, 0, 40]]}

Answer 2

if i want to do it ,first find rgb numbers for yellow (i use 'Edit colors 'in paint) then change them to HSV whith this method:

 u = np.uint8([[[0,236,236]]])
 # define range of blue color in HSV
 lower_yellow = np.array(cv2.cvtColor(l,cv2.COLOR_BGR2HSV))
 upper_yellow = np.array( cv2.cvtColor(u,cv2.COLOR_BGR2HSV))```