Vector graphics has been employed in a wide variety of applications due to its scalability and editability. Editability is a high priority for artists and designers who wish to produce vector-based graphical content with user interaction. In this paper, we introduce a new vector image representation based on piecewise smooth subdivision surfaces, which is a simple, unified and flexible framework that supports a variety of operations, including shape editing, color editing, image stylization, and vector image processing. These operations effectively create novel vector graphics by reusing and altering existing image vectorization results. Because image vectorization yields an abstraction of the original raster image, controlling the level of detail of this abstraction is highly desirable. To this end, we design a feature-oriented vector image pyramid that offers multiple levels of abstraction simultaneously. Our new vector image representation can be rasterized efficiently using GPU-accelerated subdivision. Experiments indicate that our vector image representation achieves high visual quality and better supports editing operations than existing representations.

We present a new method for interpolating both boundary values and gradients over a 2D polygonal domain. Despite various previous efforts, it remains challenging to define a closed-form interpolant that produces natural-looking functions while allowing flexible control of boundary constraints. Our method builds on an existing transfinite interpolant over a continuous domain, which in turn extends the classical mean value interpolant. We re-derive the interpolant from the mean value property of biharmonic functions, and prove that the interpolant indeed matches the gradient constraints when the boundary is piece-wise linear. We then give closed-form formula (as generalized barycentric coordinates) for boundary constraints represented as polynomials up to degree 3 (for values) and 1 (for normal derivatives) over each polygon edge. We demonstrate the flexibility and efficiency of our coordinates in two novel applications, smooth image deformation using curved cage networks and adaptive simplification of gradient meshes.

Figure 1: Several vector solid textures rendered in real time. In each group, the upper inset shows a closer view while the lower inset is rendered using the bitmap solid texture from which the vector version is generated. In the middle group, the reflectance coefficients are stored along with the RGB channels. In the rightmost group, three different scales of the same vector solid texture are composited to yield complex self-similar boundaries. In this paper, we introduce a compact random-access vector representation for solid textures made of intermixed regions with relatively smooth internal color variations. It is feature-preserving and resolution-independent. In this representation, a texture volume is divided into multiple regions. Region boundaries are implicitly defined using a signed distance function. Color variations within the regions are represented using compactly supported radial basis functions (RBFs). With a spatial indexing structure, such RBFs enable efficient color evaluation during real-time solid texture mapping. Effective techniques have been developed for generating such a vector representation from bitmap solid textures. Data structures and techniques have also been developed to compactly store region labels and distance values for efficient random access during boundary and color evaluation.

Abstract—Solid textures require large storage and are computationally expensive to synthesize. In this paper, we propose a novel solid representation called gradient solids to compactly represent solid textures, including a tricubic interpolation scheme of colors and gradients for smooth variation and a region-based approach for representing sharp boundaries. We further propose a novel approach based on this to directly synthesize gradient solid textures from exemplars. Compared to existing methods, our approach avoids the expensive step of synthesizing the complete solid textures at voxel level and produces optimized solid textures using our representation. This avoids significant amount of unnecessary computation and storage involved in the voxel-level synthesis while producing solid textures with comparable quality to the state of the art. The algorithm is much faster than existing approaches for solid texture synthesis and makes it feasible to synthesize high-resolution solid textures in full. Our compact representation also supports efficient novel applications such as instant editing propagation on full solids. Index Terms—solid textures, synthesis, vector representation, gradient 1

Abstract—Vector graphics has been employed in a wide variety of applications due to its scalability and editability. Editability is a high priority for artists and designers who wish to produce vector-based graphical content with user interaction. In this paper, we introduce a new vector image representation based on piecewise smooth subdivision surfaces, which is a simple, unified and flexible framework that supports a variety of operations, including shape editing, color editing, image stylization, and vector image processing. These operations effectively create novel vector graphics by reusing and altering existing image vectorization results. Because image vectorization yields an abstraction of the original raster image, controlling the level of detail of this abstraction is highly desirable. To this end, we design a feature-oriented vector image pyramid that offers multiple levels of abstraction simultaneously. Our new vector image representation can be rasterized efficiently using GPU-accelerated subdivision. Experiments indicate that our vector image representation achieves high visual quality and better supports editing operations than existing representations. Index Terms—Vector graphics, subdivision surfaces, multiresolution representation, vector image editing Ç 1

journal homepage: www.elsevier.com/locate/gmod

Part of the difficulty in depicting stylized materials stems from the fact that the techniques artists use to draw materials are based on accumulated artistic knowledge. These guidelines they use to dehal-00828067,

Figure 1: We describe Vector Shade Trees that represent stylized materials as a combination of basic shade nodes composed of vector graphics primitives (a). Combining these nodes allows the depiction of a variety of materials while preserving traditional vector drawing style and practice. We integrate our vector shade trees in a vector drawing tool that allows users to apply stylized shading effects on vector line drawings (b,c). This pdf contains png versions of vector art to avoid viewer compatibility problems; full vector versions of our results are in supplemental material. Original line drawing from koconmus, openclipart.org c, colored version c the authors. Vector graphics represent images with compact, editable and scalable primitives. Skillful vector artists employ these primitives to produce vivid depictions of material appearance and lighting. However, such stylized imagery often requires building complex multilayered combinations of colored fills and gradient meshes. We facilitate this task by introducing vector shade trees that bring to vector graphics the flexibility of modular shading representations as known in the 3D rendering community. In contrast to traditional shade trees that combine pixel and vertex shaders, our shade nodes encapsulate the creation and blending of vector primitives that vector artists routinely use. We propose a set of basic shade nodes that we design to respect the traditional guidelines on material depiction described in drawing books and tutorials. We integrate our representation as an Adobe Illustrator plug-in that allows even inexperienced users to take a line drawing, apply a few clicks and obtain a fully colored illustration. More experienced artists can easily refine the illustration, adding more details and visual features, while using all the vector drawing tools they are already familiar with. We demonstrate the power of our representation by quickly generating illustrations of complex objects and materials.

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Figure 1: Naïve upsampling of pixel art images leads to unsatisfactory results. Our algorithm extracts a smooth, resolution-independent vector representation from the image, which is suitable for high-resolution display devices. (Input image c ○ Nintendo Co., Ltd.). We describe a novel algorithm for extracting a resolutionindependent vector representation from pixel art images, which enables magnifying the results by an arbitrary amount without image degradation. Our algorithm resolves pixel-scale features in the input and converts them into regions with smoothly varying shading that are crisply separated by piecewise-smooth contour curves. In the original image, pixels are represented on a square pixel lattice, where diagonal neighbors are only connected through a single point. This causes thin features to become visually disconnected under magnification by conventional means, and creates ambiguities in the connectedness and separation of diagonal neighbors. The key to our algorithm is in resolving these ambiguities. This enables us to reshape the pixel cells so that neighboring pixels belonging to the same feature are connected through edges, thereby preserving the feature connectivity under magnification. We reduce pixel aliasing artifacts and improve smoothness by fitting spline curves to contours in the image and optimizing their control points.