Generating color gradient in Python

Question

i have a list of RGB colors and need to draw gradient between them in python. Have you any suggestions how to make it usin PIL library?

EDIT: I get this:

def gradient(list_of_colors):
    width = 600
    height = 480
    img = Image.new("RGB", (width, height))
    draw = ImageDraw.Draw(img)

    for i in range(len(list_of_colors)):
        r1,g1,b1 = list_of_colors[i]
        for x in range(width/len(list_of_colors)):
            colour = (r1,g1,b1)
            draw.line((x+(width/len(list_of_colors)*i), 0, x+(width/len(list_of_colors)*i), height), fill=colour)

    img.show()

gradient([(30, 198, 244), (99, 200, 72),(120, 50, 80),(200, 90, 140)])

and it draw me this: http://img59.imageshack.us/img59/1852/3gba.png

I just need to make it gradient between those colors not stripes of colors. (something like this) http://www.kees-tm.nl/uploads/colorgradient.jpg

Welcome to Stack Overflow. Your question is nearly there! For the community to better answer, please edit it to include how the output of your code does not meet your expectations, and what you have tried in the contex of PIL. For more information, please re-read stackoverflow.com/help/how-to-ask — user2363448
– user2363448, Commented Dec 14, 2013 at 17:40
Does this answer your question? How to create colour gradient in Python? — pjpscriv
– pjpscriv, Commented Oct 8, 2022 at 1:25

olegsson · Accepted Answer · 2016-07-08 10:12:20Z

3

I think code like this will work, it uses Linear Interpolation to create the gradient.

list_of_colors = [(30, 198, 244), (99, 200, 72),(120, 50, 80),(200, 90, 140)]

no_steps = 100

def LerpColour(c1,c2,t):
    return (c1[0]+(c2[0]-c1[0])*t,c1[1]+(c2[1]-c1[1])*t,c1[2]+(c2[2]-c1[2])*t)

for i in range(len(list_of_colors)-2):
    for j in range(no_steps):
        colour = LerpColour(list_of_colors[i],list_of_colors[i+1],j/no_steps)

Obviously I don't know how you are drawing the gradient so I've left it open to you, do what you like with the colour variable to draw each step of the gradient within the for loop. :)

Also: I don't understand list generation so if anyone can improve the LerpColour function to use it please edit my post :)

EDIT - Generating a list that can easily be iterated over when drawing with PIL:

gradient = []
for i in range(len(list_of_colors)-2):
    for j in range(no_steps):
        gradient.append(LerpColour(list_of_colors[i],list_of_colors[i+1],j/no_steps))

edited Jul 8, 2016 at 10:12

olegsson

1033 silver badges6 bronze badges

answered Dec 14, 2013 at 17:34

JamJar00

3594 silver badges14 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

user3102697 Over a year ago

applied you idea but still no changes, i still get lines of color not gradient

JamJar00 Over a year ago

Can you give a screenshot of what you have, and a mock up of what you want? That way I (and others) will have a better idea of what we're aiming at :)

user3102697 Over a year ago

I get this link and want something like this link for any colors i put into that list

Tcll · Accepted Answer · 2022-05-19 00:03:03Z

0

I've built my own thing for my own needs after trying to find something that could compute gradients efficiently on multi-dimensional arrays so I hope you don't mind alpha processing :)

def colorscale( r:int,g:int,b:int,a:int, R:int,G:int,B:int,A:int, s:float ) -> tuple:
    S = 1.-s
    return round(r*S+R*s),round(g*S+G*s),round(b*S+B*s),round(a*S+A*s)

this takes the same approach as JamJar's LerpColour, but I did the scaling in a more simplistic way.

though it's probably not the most efficient due to round(), but I needed the accuracy...

that said, alternatively you can use scalar (0.0 - 1.0) colors (like I am), to get rid of round() entirely ;)

def colorscale( r:float,g:float,b:float,a:float, R:float,G:float,B:float,A:float, s:float ) -> tuple:
    S = 1.-s
    return r*S+R*s,g*S+G*s,b*S+B*s,a*S+A*s

anyways, I know it's a late response, but I hope this answer helps anyone who needs it.

answered May 19, 2022 at 0:03

Tcll

7,4311 gold badge22 silver badges25 bronze badges

1 Comment

Mark Ransom Over a year ago

Linear interpolation is probably the most common way to create a gradient, but it's rarely the best.

Collectives™ on Stack Overflow

Generating color gradient in Python

2 Answers 2

3 Comments

1 Comment

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

3 Comments

1 Comment

Your Answer

Sign up or log in

Post as a guest

Linked

Related