A error with using cv2.cvtColor to convert BGR img to HSV

Expected behaviour

The Hue value of one color value is 180 , the return value should be 180 , but it return 0.
it will make the average value be impacted very much.

Actual behaviour

I tried to use cv2.cvtColor convert 2 similar pure color pictures to HSV and compare with the Hue result,
I found the delta of them near to 50%,

until I print both of them , that be found like this :

6

h_top [ 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 178 178 178 178 178 178 178
178 178 178 178 178 178 178 178 178 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 178 178 178 178 178 178 178 178 178 178 178 178 178
178 178 178 178 178 178 178 178 178 178 178 178 178 178 178 178 178 178
178 178 178 178 178 178 178 178 178 178 178 178 178 178 178 178 178 178
178 178 178 178 178 178 178 178 178 178 178 178 178 178 178 178 178 178
178 178 178 178 178 178 178 178 178 178 178 178 178 178 178 178 178 178
178 178 178 178 178 178 178 178 178 178 178 178 178 178 178 178 178 178
178 178 178 178 178 178 178 178 178 178 178 178 178 178 178]
s_top 42.46882456140351
v_top 96.90878947368421
h_bottom [177 177 177 177 177 177 177 178 178 178 178 178 178 178 178 178 178 178
178 178 178 178 178 178 178 178 178 178 178 178 178 178 178 178 178 178
178 178 178 178 178 178 178 178 178 178 178 178 178 178 178 178 178 178
178 178 178 178 178 178 178 178 178 178 178 178 178 178 178 178 178 178
177 177 177 177 177 177 177 177 177 177 177 177 177 177 178 178 178 178
178 178 178 178 178 178 178 178 178 178 178 178 178 178 178 178 178 178
178 178 178 178 178 178 178 178 178 178 178 178 178 178 178 178 178 178
178 178 178 178 178 178 178 178 178 178 178 178 178 178 178 178 178 178
178 178 178 178 178 178 178 178 178 178 178 178 178 178 178 178 178 178
178 178 178 178 178 178 178 178 178 178 178 178 178 178 178 178 178 178
178 178 178 178 178 178 178 178 178 178 178 178 178 178 178 178 178 178
178 178 178 178 178 178 178 178 178 178 178 178 178 178 178 178 178 178
178 178 178 178 178 178 178 178 178 178 178 178 178 178 178 178 178 178
178 178 178 178 178 178 178 178 178 178 178 178 178 178 178 178 178 178
178 178 178 178 178 178 178 178 178 178 178 178 178 178 178 178 178 178
178 178 178 178 178 178 178 178 178 178 178 178 178 178 178]
s_bottom 43.50040350877193
v_bottom 95.66519298245613

h_top and h_bottom are the similar pictures I got.

Steps to reproduce

use this to drop the zero data for short term
non_zero_h = hsv_piece[:,:, 0][hsv_piece[:,:, 0] > 0]

windows 10
opencv-python 4.5.5

Issue submission checklist

• This is not a generic OpenCV usage question (looking for help for coding, other usage questions, homework etc.)
• I have read the README of this repository and understand that this repository provides only an automated build toolchain for OpenCV Python packages (there is no actual OpenCV code here)
• The issue is related to the build scripts in this repository, to the pre-built binaries or is a feature request (such as "please enable this additional dependency")
• I'm using the latest version of opencv-python

No repository file or test is named. Start by checking whether the reported cv2.cvtColor behavior belongs to opencv-python's packaging or to OpenCV itself, using the stated Windows 10 and opencv-python 4.5.5 context. Done would require a reproducible, repository-scoped failure or a clear indication that no build-toolchain change is needed.