Ruen-Rone Lee

Halftone QR codes

QR code is a popular form of barcode pattern that is ubiquitously used to tag information to products or for linking advertisements. While, on one hand, it is essential to keep the patterns machine-readable; on the other hand, even small changes to the patterns can easily render them unreadable. Hence, in absence of any computational support, such QR codes appear as random collections of black/white modules, and are often visually unpleasant. We propose an approach to produce high quality visual QR codes, which we call halftone QR codes, that are still machine-readable. First, we build a pattern readability function wherein we learn a probability distribution of what modules can be replaced by which other modules. Then, given a text tag, we express the input image in terms of the learned dictionary to encode the source text. We demonstrate that our approach produces high quality results on a range of inputs and under different distortion effects.

Real-time correction of wide-angle lens distortion for images with GPU computing

Wide-angle lens provides a broad field of view which benefits some applications, such as video surveillance or endoscopic imaging. However, it also induces lens distortion, especially radial distortion, which may impede further video analysis or perceptual interpretation. For some applications, such as minimally invasive surgery and visual surveillance, real-time correction of image distortion is required. Traditional CPU-centric machines are difficult to achieve the requirement of real-time computation because of a large amount of computation. In this paper, we propose to achieve real-time correction of wide-angle lens distortion of images on several target platforms. In the GPGPU platform, we achieve real-time correction at full-HD resolution by using CUDA. For middle-end devices, an error-controllable mesh is used and the system is implemented by industry standard, OpenGL. We also implement it with OpenGL ES on embedded GPUs for mobile devices. Experiments show using our error-controllable mesh greatly outperforms those using regularly downsampled meshes.

Pixel2Brick: Constructing Brick Sculptures from Pixel Art

LEGO®, a popular brick‐based toy construction system, provides an affordable and convenient way of fabricating geometric shapes. However, building arbitrary shapes using LEGO bricks with restrictive colors and sizes is not trivial. It requires careful design process to produce appealing, stable and constructable brick sculptures. In this work, we investigate the novel problem of constructing brick sculptures from pixel art images. In contrast to previous efforts that focus on 3D models, pixel art contains rich visual contents for generating engaging LEGO designs. On the other hand, the characteristics of pixel art and corresponding brick sculpture pose new challenges to the design process. We present Pixel2Brick, a novel computational framework to automatically construct brick sculptures from pixel art. This is based on implementing a set of design guidelines concerning the visual quality as well as the structural stability of built sculptures. We demonstrate the effectiveness of our framework with various brick sculptures (both real and virtual) generated from a variety of pixel art images. Experimental results show that our framework is efficient and gains significant improvements over state‐of‐the‐arts.

Tone- and Feature-Aware Circular Scribble Art

Circular scribble art is a kind of line drawing where the seemingly random, noisy and shapeless circular scribbles at microscopic scale constitute astonishing grayscale images at macroscopic scale. Such a delicate skill has rendered the creation of circular scribble art a tedious and time‐consuming task even for gifted artists. In this work, we present a novel method for automatic synthesis of circular scribble art. The synthesis problem is modeled as tracing along a virtual path using a parametric circular curve. To reproduce the tone and important edge structure of input grayscale images, the system adaptively adjusts the density and structure of virtual path, and dynamically controls the size, drawing speed and orientation of parametric circular curve during the synthesis. We demonstrate the potential of our system using several circular scribble images synthesized from a wide variety of grayscale images. A preliminary experimental studying is conducted to qualitatively and quantitatively evaluate our method. Results report that our method is efficient and generates convincing results comparable to artistic artworks.

3D Spinal Cord and Nerves Segmentation from STIR-MRI

In this paper, we present a system for spinal cord and nerves segmentation from STIR-MRI. We propose an user interactive segmentation method for 3D images, which is extended from the 2D random walker algorithm and implemented with a slice-section strategy. After obtaining the 3D segmentation result, we build the 3D spinal cord and nerves model for each view using VTK, which is an open-source, freely available software. Then we obtain the point cloud of the spinal cord and nerves surface by registering the three surface models constructed from three STIR-MRI images of different directions. In the experimental results, we show the 3D segmentation results of spinal cord and nerves from the STIR-MRI (Short Tau Inversion Recovery - Magnetic Resonance Imaging)images in three different views, and also display the reconstructed 3D surface model.

On mapping Bezier curve and surface subdivision algorithms into a hypercube with geometric adjacency constraint

The authors discuss the Bezier curve and surface generation algorithms on a hypercube computer. They show that the computation structures of Bezier curve and surface generation based on subdivision method can be modeled as binomial trees and extended binomial trees respectively. Properties of binomial trees and extended binomial trees are explored and mappings from these tree structures to hypercubes are discussed. As the spatial coherence plays an important role in computer graphics and geometric algorithms, the authors imposed the geometric adjacency on these mappings and proved that there exist adjacency preserving mappings. Moreover, they show that their mappings are optimal with respect to expansion, dilation and congestion.<<ETX>>

Emerging images synthesis from photographs

Emergence refers to a phenomenon by which human perceives complete objects in a seemingly noisy image not by recognizing local parts of image but viewing the image as a whole. The Dalmatian dog image created by R. C. James is probably the best demonstration of emergence [Bach 2002]. It shows that local windows from the image reveal nothing but meaningless, complex and random black splats. Only when the image is viewed as a whole, a Dalmatian dog suddenly appears. The absence of meaningful information in local image parts largely hinders existing computer vision algorithms from recognizing emerging figures. Therefore, it makes the emergence an new type of CAPTCHA to tell human and machine apart.

Continuous circular scribble arts

Scribble art is a kind of illustrative drawing. Artists use continuous lines to convey the impression of an image or concept of a design. Unlike conventional line drawings such as sketching and hatching that commonly comprise of short and straight line segments, scribble artists aim at depicting the image with long and continuous curves. In this work, we study a typical curve pattern, circular scribble that appears most frequently in the artworks. Circular lines are drawn in either clockwise or counter-clockwise direction with varying radius in the circular scribble arts. The artists delicately trace along a seemingly random path and control the size and orientation of circular line pattern to depict a subject of their artwork. The main challenges lie in producing smooth transition between grayscale levels and preserving dominant image features using continuous loops and intersections of a circular scribble. Thus, the creation of circular scribble art is skill-demanding and time-consuming. In order to facilitate such process, we introduce a systematic approach to automatically synthesize circular scribble arts from images by tracing along a virtual path using solely a single continuous circular scribble with varying radius and orientation. We have tested our approach using a wide range of images and generate visually pleasing circular scribble arts (see Figure 1).

Pixel Art Color Palette Synthesis

Pixel art is created together with a color palette which greatly affects the overall visual quality. From a given image with hundreds of thousands of colors, it is difficult to pick out a limited number of colors for the color palette. We propose an automatic system, which adopts similar steps of the manual creation processes by pixel art artists, to effectively synthesize the color palette of a pixel art from a given image. Based on our approach, both artists and novices can easily derive a low-resolution image which is very close to the required final pixel art.

Fixit: A 3D Jigsaw Puzzle Game Using Multi-touch Gestures

We propose Fixit, a 3D jigsaw puzzle game using touch gestures on Android mobile devices. The system consists of a back-end authoring process and afront-end gaming control. The authoring process generates thepuzzle pieces, which are cut and refined by our algorithms from the input 3D model. The gaming control providesan intuitivegraphical user interface, which utilize touch screen multimodal gestures and allows user to reconstruct the 3Djigsaw puzzle pieces into the original 3D model.