Decomposing Digital Paintings into Layers via RGB-space Geometry

TL;DR

This paper introduces a novel method to decompose digital paintings into layers by analyzing RGB-space geometry, enabling better editing and understanding of digital artwork.

Contribution

It presents a new RGB-space geometric approach to decompose images into layers with transparent coats, improving digital painting editing capabilities.

Findings

Effective layer decomposition based on RGB-space convex hulls

Ability to control layer complexity and order

Facilitates re-editing of digital paintings

Abstract

In digital painting software, layers organize paintings. However, layers are not explicitly represented, transmitted, or published with the final digital painting. We propose a technique to decompose a digital painting into layers. In our decomposition, each layer represents a coat of paint of a single paint color applied with varying opacity throughout the image. Our decomposition is based on the painting's RGB-space geometry. In RGB-space, a geometric structure is revealed due to the linear nature of the standard Porter-Duff "over" pixel compositing operation. The vertices of the convex hull of pixels in RGB-space suggest paint colors. Users choose the degree of simplification to perform on the convex hull, as well as a layer order for the colors. We solve a constrained optimization problem to find maximally translucent, spatially coherent opacity for each layer, such that the composition of the layers reproduces the original image. We demonstrate the utility of the resulting decompositions for re-editing.