Convert image to Gimp gradient

image2gradient.py

import sys
import cv2
import numpy as np

"""
Convert image to Gimp gradient.

Usage: python image2gradient.py input_image
Output gradient in stdout. Place it in something like
~/.config/GIMP/2.x/gradients or
~/.gimp-2.x/gradients
(usually in a .ggr file but any extention will do the job)

Requires opencv2. But it is easy to adapt to some other image loading library.
"""


def convert(p):
	"""Convert BGR byte-encoded color to gimp gradient color"""
	return '%f %f %f %f' % (p[2] / 255.0, p[1] / 255.0, p[0] / 255.0, 1.0)

# Check arguments
if len(sys.argv) < 2:
	print("Usage: %s input_image" % (sys.argv,))
	exit(0)

# Load Image
im = cv2.imread(sys.argv[1])


# Get keys
old_p = None
count = 0
keys = []
for l in im:
	p = list(l[0])
	# Add a key at each color change
	if (old_p != p):
		if count > 0:
			keys.append((convert(old_p), count))
		count = 0
	count += 1
	old_p = p
keys.append((convert(old_p), count))


total = sum([k[1] for k in keys[1:]])


# Write file
print('GIMP Gradient')
print('Name: ' + sys.argv[1].split('/')[-1].split('.')[0]) # Name of input file
print(len(keys) - 1)

old_k = None
offset = 0.0
for k, c in keys:
	if old_k:
		begin = offset / total
		end = (offset + c) / total
		print('%f %f %f %s %s 0 0 0 0' % (begin, (begin + end) / 2.0, end, old_k, k))
		offset += c
	old_k = k