Pixel art is a modern digital art in which high resolution images are abstracted into low resolution pixelated outputs using concise outlines and reduced color palettes. Creating pixel art is a labor intensive and skill-demanding process due to the challenge of using limited pixels to represent complicated shapes. Not surprisingly, generating pixel art animation is even harder given the additional constraints imposed in the temporal domain. Although many powerful editors have been designed to facilitate the creation of still pixel art images, the extension to pixel art animation remains an unexplored direction. Existing systems typically request users to craft individual pixels frame by frame, which is a tedious and error-prone process. In this work, we present a novel animation framework tailored to pixel art images. Our system bases on conventional key-frame animation framework and state-of-the-art image warping techniques to generate an initial animation sequence. The system then jointly optimizes the prominent feature lines of individual frames respecting three metrics that capture the quality of the animation sequence in both spatial and temporal domains. We demonstrate our system by generating visually pleasing animations on a variety of pixel art images, which would otherwise be difficult by applying state-of-the-art techniques due to severe artifacts.

Overview: Given an input pixel art image, our system first (a) extracts all feature pixels and constructs a set of feature lines in a preprocessing step. (b) Based on as-rigid-as-possible shape deformation and interpolation, key frames and intermediate frames are created as the initial animation sequence. (c) The feature lines of all the frames are further optimized to improve the visual quality and temporal coherence of the animation sequence. Finally, our system fills colors in the region bounded by feature lines (Input image: “Dove”© WhyMe).

We are grateful to the anonymous reviewers for their comments and suggestions. The work was supported in part by the Ministry of Science and Technology of Taiwan (103-2221-E-007-065-MY3, 105-2221-E-007-104-MY2 and 104-2218-E-004-003), EPSRC Grant EP/K02339X/1 and EP/M023281/1.

@article{Kuo:2016:FPA,

author = {Ming-Hsun Kuo and Yong-Liang Yang and Hung-Kuo Chu},

title = {Feature-Aware Pixel Art Animation},

journal = {Computer Graphics Forum (Proc. Pacific Graphics)},

volume = {35},

issue = {7},

year = {2016},

}