Palette-based Recoloring* A fast, real-time and intuitive way to - - PowerPoint PPT Presentation

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Oct 18, 2023 168 likes •341 views

Palette-based Recoloring* A fast, real-time and intuitive way to re-colorize photos for non-experts. * Based on the Palette-Based Photo Recoloring paper from Huiwen Chang, Ohad Fried, Yiming Liu, Stephen DiVerdi and Adam Finkelstein.

SLIDE 1

Palette-based Recoloring*

A fast, real-time and intuitive way to re-colorize photos for non-experts.

* Based on the “Palette-Based Photo Recoloring” paper from Huiwen Chang, Ohad Fried, Yiming Liu, Stephen DiVerdi and Adam Finkelstein.

SLIDE 2

Objectives

I'd just like to change the fox's fur. How to do it?
How to preserve the brown tones on the fur?
Do I need to be a Photoshop expert to do it?

SLIDE 3

Palette selection

We want a good set of representing colors
We use a deterministic weighted K-means

algorithm to get them.

SLIDE 4

How we do it

First we make a 15x15x15 bins in RGB space

and histogram using colors in the picture.

Use that as the input for the weighted

deterministic K-means algorithm.

The first means are set as the the bins with

highest frequency.

Distances are computed in Lab space.

SLIDE 5

Changing the K value

K value can be used to localize color edition.

K = 6 K = 3

SLIDE 6

Color edition

As seen, we find the initial palette by clustering.
Now, we use it as a control for color edition.
How to re-colorize each pixel in a natural way?

Original Palette New Palette

SLIDE 7

Two-step Color Transfer Function

First we define a L-based transfer function
Then an ab-based one using that L-slide.

SLIDE 8

Single ab-transfer function

In the case where

there is just ONE palette color, we change every pixel “almost” int the same direction.

Points

near the border have to remain in gamut.

SLIDE 9

Single ab-transfer function construction. Points near the gamut frontier are set to stay in and towards C'

SLIDE 10

General ab-based transfer function

In the general case,

we blend all directions with proper weights.

The closer the pixel

color is to a changed palette color, the more similar it changes in that direction.

SLIDE 11

General ab-transfer function construction equations.

For any color x

SLIDE 12

Implementation (too buggy for now)

SLIDE 13

Now it is possible to do this without dying in the trying.

SLIDE 14

Future work

Add some spacial awareness to the algorithm.
Fix the big obscure bugs the implementation
has. Yes, those awful red pixels are not part of

the algorithm.

Software optimizations to make the program