KytraScript/python-color-transfer

Three methods of color transfer implemented in python.

Color Transfer in Python

Three methods of color transfer implemented in Python.

Output Examples

Input image	Reference image	Mean std transfer	Lab mean transfer	Pdf transfer + Regrain

Methods

Let input image be $I$, reference image be $R$ and output image be $O$. Let $f{I}(r, g, b)$, $f{R}(r, g, b)$ be probability density functions of $I$ and $R$'s rgb values.

• Mean std transfer

  $$O = (I - mean(I)) / std(I) * std(R) + mean(R).$$

• Lab mean transfer¹

  $$I' = rgb2lab(I)$$ $$R' = rgb2lab(R)$$ $$O' = (I' - mean(I')) / std(I') * std(R') + mean(R')$$ $$O = lab2rgb(O')$$

• Pdf transfer²

  $O = t(I)$, where $t: R^3\rightarrow R^3$ is a continous mapping so that $f{t(I)}(r, g, b) = f{R}(r, g, b)$.

Requirements

• 🐍 python>=3.6

Installation

From PyPi

pip install python-color-transfer

From source

git clone https://github.com/pengbo-learn/python-color-transfer.git
cd python-color-transfer

pip install -r requirements.txt

Demo

• To replicate the results in Output Examples, run:

python demo.py 

Output

demo_images/house.jpeg: 512x768x3
demo_images/hats.png: 512x768x3
Pdf transfer time: 1.47s
Regrain time: 1.16s
Mean std transfer time: 0.09s
Lab Mean std transfer time: 0.09s
Saved to demo_images/house_display.png

demo_images/fallingwater.png: 727x483x3
demo_images/autumn.jpg: 727x1000x3
Pdf transfer time: 1.87s
Regrain time: 0.87s
Mean std transfer time: 0.12s
Lab Mean std transfer time: 0.11s
Saved to demo_images/fallingwater_display.png

demo_images/tower.jpeg: 743x1280x3
demo_images/sunset.jpg: 743x1114x3
Pdf transfer time: 2.95s
Regrain time: 2.83s
Mean std transfer time: 0.23s
Lab Mean std transfer time: 0.21s
Saved to demo_images/tower_display.png
  
demo_images/scotland_house.png: 361x481x3
demo_images/scotland_plain.png: 361x481x3
Pdf transfer time: 0.67s
Regrain time: 0.49s
Mean std transfer time: 0.04s
Lab Mean std transfer time: 0.22s
Saved to demo_images/scotland_display.png

Usage

from pathlib import Path

import cv2
from python_color_transfer.color_transfer import ColorTransfer

# Using demo images
input_image = 'demo_images/house.jpeg'
ref_image = 'demo_images/hats.png'

# input image and reference image
img_arr_in = cv2.imread(input_image)
img_arr_ref = cv2.imread(ref_image)

# Initialize the class
PT = ColorTransfer()

# Pdf transfer
img_arr_pdf_reg = PT.pdf_transfer(img_arr_in=img_arr_in,
                                  img_arr_ref=img_arr_ref,
                                  regrain=True)
# Mean std transfer
img_arr_mt = PT.mean_std_transfer(img_arr_in=img_arr_in,
                                  img_arr_ref=img_arr_ref)
# Lab mean transfer
img_arr_lt = PT.lab_transfer(img_arr_in=img_arr_in, img_arr_ref=img_arr_ref)

# Save the example results
img_name = Path(input_image).stem
for method, img in [('pdf-reg', img_arr_pdf_reg), ('mt', img_arr_mt),
                   ('lt', img_arr_lt)]:
    cv2.imwrite(f'{img_name}_{method}.jpg', img)

Footnotes

1. Lab mean transfer: Color Transfer between Images by Erik Reinhard, Michael Ashikhmin, Bruce Gooch and Peter Shirley.
   Open source's python implementation ↩

2. Pdf transfer: Automated colour grading using colour distribution transfer by F. Pitie , A. Kokaram and R. Dahyot.
   Author's matlab implementation ↩