  We present a palette-based framework for color composition for visual
applications. Color composition is a critical aspect of visual applications in
art, design, and visualization. The color wheel is often used to explain
pleasing color combinations in geometric terms, and, in digital design, to
provide a user interface to visualize and manipulate colors. We abstract
relationships between palette colors as a compact set of axes describing
harmonic templates over perceptually uniform color wheels. Our framework
provides a basis for a variety of color-aware image operations, such as color
harmonization and color transfer, and can be applied to videos. To enable our
approach, we introduce an extremely scalable and efficient yet simple
palette-based image decomposition algorithm. Our approach is based on the
geometry of images in RGBXY-space. This new geometric approach is orders of
magnitude more efficient than previous work and requires no numerical
optimization. We demonstrate a real-time layer decomposition tool. After
preprocessing, our algorithm can decompose 6 MP images into layers in 20
milliseconds. We also conducted three large-scale, wide-ranging perceptual
studies on the perception of harmonic colors and harmonization algorithms.
