Draw a scale which ranges from red to green in Tkinter - python-3.x

Question

I would like to draw a scale which ranges from red to green. I managed to do a scale which ranges from green to yellow. Now I have 2 possible solutions :
Either drawing 2 gradients : one from red to yellow and one from yellow to green. Then I can link the 2 drawings.
Or the better solution I think : Drawing one gradient from red to green with a checkpoint on the yellow.
How to implement this second solution ?
Here is my code from green to yellow. You can test it.
import tkinter as tk
class Example(tk.Frame):
def __init__(self, parent):
tk.Frame.__init__(self, parent)
f = GradientFrame(root)
f.pack(fill="both", expand=True)
class GradientFrame(tk.Canvas):
'''A gradient frame which uses a canvas to draw the background'''
def __init__(self, parent, borderwidth=1, relief="sunken"):
tk.Canvas.__init__(self, parent, borderwidth=borderwidth, relief=relief)
self._color1 = "green"
self._color2 = "yellow"
self._color3 = "red"
self.bind("<Configure>", self._draw_gradient)
def _draw_gradient(self, event=None):
'''Draw the gradient'''
self.delete("gradient")
width = 200
height = 50
limit = width
(r1,g1,b1) = self.winfo_rgb(self._color1)
(r2,g2,b2) = self.winfo_rgb(self._color2)
(r3,g3,b3) = self.winfo_rgb(self._color3)
r_ratio = float((r2-r1)) / limit
g_ratio = float((g2-g1)) / limit
b_ratio = float((b2-b1)) / limit
for i in range(limit):
nr = int(r1 + (r_ratio * i))
ng = int(g1 + (g_ratio * i))
nb = int(b1 + (b_ratio * i))
color = "#%4.4x%4.4x%4.4x" % (nr,ng,nb)
self.create_line(0,i,height,i, tags=("gradient",), fill=color)
self.lower("gradient")
for i in range(limit):
nr = int(r1 + (r_ratio * i))
ng = int(g1 + (g_ratio * i))
nb = int(b1 + (b_ratio * i))
color = "#%4.4x%4.4x%4.4x" % (nr,ng,nb)
self.create_line(0,i,height,i, tags=("gradient",), fill=color)
self.lower("gradient")
if __name__ == "__main__":
root = tk.Tk()
Example(root).pack(fill="both", expand=True)
root.mainloop()

Answer 1

Without the generalization or general aesthetics of the above code, I offer you a simple solution (implemented against the red to green gradient) here:
import tkinter
def rgb(r, g, b):
return "#%s%s%s" % tuple([hex(c)[2:].rjust(2, "0") for c in (r, g, b)])
root = tkinter.Tk()
root.title("Gradient")
gradient1 = tkinter.Canvas(root, width=255*2, height=50)
gradient1.pack()
gradient2 = tkinter.Canvas(root, width=255*2, height=50)
gradient2.pack()
for x in range(0, 256):
r = x
g = 255-x
gradient1.create_rectangle(x*2, 0, x*2 + 2, 50, fill=rgb(r, g, 0),
outline=rgb(r, g, 0))
for x in range(0, 256):
r = x*2 if x < 128 else 255
g = 255 if x < 128 else 255 - (x-128)*2
gradient2.create_rectangle(x*2, 0, x*2 + 2, 50, fill=rgb(r, g, 0),
outline=rgb(r, g, 0))
I believe it's what you meant by "yellow checkpoints". Thanks for the challenge! :^)