Recolor image to other base color and keeping the gradients

Question

I want to recolor an image to another base color but thereby keeping the gradients. For example in this picture the base color is green.

and I want to change this to base color Blue for example (RGB: 0,119,153). I used the following python code:

import numpy as np
import cv2
dg = [0,59,10]
mg = [0,91,16]
lg = [0,106,18]
db = [92,71,0]
mb = [153,119,0]
lb = [204,163,93]

im = cv2.imread("C:/Temp/recolor_source.png")
im[np.where((im == dg).all(axis=2))] = db
im[np.where((im == mg).all(axis=2))] = mb
im[np.where((im == lg).all(axis=2))] = lb
cv2.imwrite("C:/Temp/recolor_result.png", im)

which gives the following result:

There is still quite some green around the white text and in the grayed-out button in the resulting image. What is the right approach to convert to another base color and keeping all the gradients?

Answer 1

This is the answer as suggested by Mark Setchell.

import cv2

im = cv2.imread("C:/Temp/recolor_source.png")
hsv = cv2.cvtColor(im, cv2.COLOR_BGR2HSV)
hchannel = hsv[:, :, 0]
hchannel = 40 + hchannel
hsv[:, :, 0] = hchannel
rgb = cv2.cvtColor(hsv, cv2.COLOR_HSV2BGR)

cv2.imwrite("C:/Temp/recolor_result.png", rgb)

Resulting in: