Space-Optimized Texture Maps

To meet various transmission and storage constraints, it is desirable that a compression algorithm allows a range of compression ratios. In this paper we analyze the JPEG compression algorithm, the international standard for compressing continuous tone images, and show how higher compression ratios can be achieved with minimal loss in image quality. We compare three methods to achieve variable compression with JPEG. Through a comprehensive analysis using 8 standard monochrome images from the USC database, we propose a method that offers substantial visual quality advantages for high compression ratios. The comparisons have been made by using an objective distortion measure which corresponds well to subjective assessments of visual quality. The paper provides detailed motivation for the algorithms, and suggests the choice of parameters to obtain variable compression with minimal loss in visual quality. >

Color bit-depth is an important attribute to image quality. However, the precision in various image capture devices limits the color bit-depth and introduces loss in visual quality. Expanding the color bit-depth is an important image enhancement issue. A good bit-depth expansion system manipulates low color bit-depth image for best visual quality as displayed on high color bit-depth monitors. However, in most color bit-depth expansion algorithms, severe contouring effect is observed in smooth gradient area which degrades the visual quality. In this paper, a novel approach is proposed. By considering the distance from contour edges, fine gradient value are applied to fill the contour gaps to achieve gradual transaction.

In this paper, an innovative method of HEVC video pre-processing is proposed. The method applies a simple linear iterative clustering (SLIC), which adapts a k-means clustering to group pixels into perceptually meaningful atomic regions of superpixels. By calculating the average of weighted average of luminance differences around each pixel in the superpixel, a suitable parameter of Gaussian filter for the superpixel is determined. Experimental results show that bit rate can be reduced up to 29% without loss in visual quality.

Patient motion is inevitable in SPECT and PET due to the lengthy period of time patients are imaged and patient motion can degrade diagnostic accuracy. The goal of our studies is to perfect a methodology for tracking and correcting patient motion when it occurs. In this paper we report on enhancements to the calibration, camera stability, accuracy of motion tracking, and temporal synchronization of a low-cost visual tracking system (VTS) we are developing. The purpose of the VTS is to track the motion of retro-reflective markers on stretchy bands wrapped about the chest and abdomen of patients. We have improved the accuracy of 3D spatial calibration by using a MATLAB optical camera calibration package with a planar calibration pattern. This allowed us to determine the intrinsic and extrinsic parameters for stereo-imaging with our CCD cameras. Locations in the VTS coordinate system are transformed to the SPECT coordinate system by a VTS/SPECT mapping using a phantom of 7 retro-reflective spheres each filled with a drop of Tc(99m). We switched from pan, tilt and zoom (PTZ) network cameras to fixed network cameras to reduce the amount of camera drift. The improved stability was verified by tracking the positions of fixed retro-reflective markers on a wall. The ability of our VTS to track movement, on average, with sub-millimeter and sub-degree accuracy was established with the 7-sphere phantom for 1 cm vertical and axial steps as well as for an arbitrary rotation and translation. The difference in the time of optical image acquisition as decoded from the image headers relative to synchronization signals sent to the SPECT system was used to establish temporal synchrony between optical and list-mode SPECT acquisition. Two experiments showed better than 100 ms agreement between VTS and SPECT observed motion for three axial translations. We were able to track 3 reflective markers on an anthropomorphic phantom with a precision that allowed us to correct motion such that no loss in visual quality was noted in motion corrected slices relative to motion free slices.

This paper presents a technique for representing and displaying high dynamic-range texture maps (HDRTMs) using current graphics hardware. Dynamic range in real-world environments often far exceeds the range representable in 8-bit per-channel texture maps. The increased realism afforded by a highdynamic range representation provides improved fidelity and expressiveness for interactive visualization of image-based models. Our technique allows for realtime rendering of scenes with arbitrary dynamic range, limited only by available texture memory. In our technique, high-dynamic range textures are decomposed into sets of 8- bit textures. These 8-bit textures are dynamically reassembled by the graphics hardware's programmable multitexturing system or using multipass techniques and framebuffer image processing. These operations allow the exposure level of the texture to be adjusted continuously and arbitrarily at the time of rendering, correctly accounting for the gamma curve and dynamic range restrictions of the display device. Further, for any given exposure only two 8-bit textures must be resident in texture memory simultaneously. We present implementation details of this technique on various 3D graphics hardware architectures. We demonstrate several applications, including high-dynamic range panoramic viewing with simulated auto-exposure, real-time radiance environment mapping, and simulated Fresnel reflection.

In this contribution, we propose a near lossless compression algorithm for Color Filter Arrays (CFA) images. It allows higher compression ratio than any strictly lossless algorithm for the price of some small and controllable error. In our approach a structural transformation is applied first in order to pack the pixels of the same color in a structure appropriate for the subsequent compression algorithm. The transformed data is compressed with a modified version of the JPEG-LS algorithm. A nonlinear and adaptive error quantization function is embedded in the JPEG-LS algorithm after the fixed and context adaptive predictors. It is step-like and adapts to the base signal level in such a manner that higher error values are allowed for lighter parts with no visual quality loss. These higher error values are then suppressed by gamma correction applied during the image reconstruction stage. The algorithm can be adjusted for arbitrary pixel resolution, gamma value and tolerated error range. The compression performance of the proposed algorithm has been tested for real CFA raw data. The results are presented in terms of compression ratio versus reconstruction error and the visual quality of the reconstructed images is demonstrated as well.

This chapter discusses the use of textures for representing surface detail, shadows, and reflections. The use of texture mapping and animation together readily produces truly dramatic aliasing, and much of the complexity of texture mapping systems is created by the antialiasing measures that are used to tame the artifacts. Designing the texture coordinate function well is a key requirement for getting good results with texture mapping. Geometrically determined texture coordinates are used for simple shapes or special situations, as a quick solution, or as a starting point for designing a hand-tweaked texture coordinate map. Surfaces that are roughly spherical in shape can be parameterized using a texture coordinate function that maps a point on the surface to a point on a sphere using radial projection: take a line from the center of the sphere through the point on the surface, and find the intersection with the sph.

The problem of energy conservation in wireless image sensor networks is addressed, and a fast zonal discrete consine transform (DCT) design which aims to decrease the complexity of JPEG baseline compression is presented. Energy consumption measurements have been made on a real wireless camera node in order to evaluate the amount of energy which can be saved during the image compression process without loss of visual quality. Although the gain depends on the compression rate, such a DCT design is a simple and effective way to prolong the lifetime of the camera nodes, and thereby the network lifetime.

Over the last few decades, the Chilean Government has constantly promoted the construction of private highways in order to increase the effectiveness in terms of transportation of goods and people all along the country. In this way, heavy road infrastructures, landscape fragmentation, loss of endangered animals’ habitat, loss of visual quality, and a decrease of biodiversity patches have emerged. Despite this, some greenery – native and introduced flora/fauna, natural elements, colors, lines, patterns, among others- can be partly seen in certain areas of Chilean highways. In particular, this paper focuses on the main route connecting Puerto Montt and Pargua cities in Los Lagos region.The objectives of this qualitative research are threefold. Firstly, to measure main Landscape attributes and Visual scale characteristics through a fieldwork by the roadside of Pargua highway (Alto Bonito Area) using a scale of attributes adapted from Tveit et al. (2007). Secondly, to measure the type of vegetation through an environmental inventory (phytosociological analysis). Thirdly, to measure the degree of management of the highway considering its maintenance and human intervention.Wilderness and Naturalness are scarcely observed on the roadside due to a concentrated presence of human interventions such as landfills and overpasses. The visual scale is checked in fieldwork from several scopes. On the southeast side of the road, Las Canchas Area is covered by high trees, houses, and industries which hinder the view of the natural surrounding landscape. On the right side of the road, it presents a clear skyline of Calbuco and Osorno volcanoes. Finally, any management of high quality of the visual scenery of this type of landscape from the route concessionaire is is randomly done. However, the vegetation surface itself has been working out a way to protect the land from erosion and desertification.

In the report, we address a problem of high resolution image representation by the sets of primitive structures (geometric models) in a wide range of scales for the aims of effective image processing and patterns manipulation. While various methods of vectorization of high resolution images have been reported in the literature, professional computer-graphics tools implement geometric models that allow representation of only synthetic images like cartoons. Processing and animation of high resolution real-world images requires novel geometric models, which allow representation of complex patterns with arbitrary visual structures. The major problem in this field is a geometric representation of the images in the fine scale without loss of visual quality. In the report, we present a novel vectorization method, which completely solves the indicated problem.

This paper describes a combined method of facial reconstruction and morphing between two heads, showing the extensive usage of feature points detected from pictures. We first present an efficient method to generate a 3D head for animation from picture data and then a simple method to do 3D-shape interpolation and 2D morphing based on triangulation. The basic idea is to generate an individualized head modified from a generic model using orthogonal picture input, then process automatic texture mapping with texture image generation by combining orthogonal pictures and coordinate generation by projection from a resulted head in front, right and left views, which results a nice triangulation on texture image. Then an intermediate shape can be obtained from interpolation between two different persons. The morphing between 2D images is processed by generating an intermediate image and new texture coordinate. Texture coordinates are interpolated linearly, and the texture image is created using Barycentric coordinates for each pixel in each triangle given from a 3D head. Various experiments, with different ratio between shape, images and various expressions, are illustrated.Keywordsclonea generic modelautomatic texture mappinginterpolationBarycentric coordinateimage morphingexpression

Texture mapping greatly influences the performance of visualization in many 3D applications. Sometimes the texture data is so large that it has to be stored in slower external storage, rather than fast texture memory or host memory. In these circumstances, texture mapping becomes the performance bottleneck. In this paper, we present a compact multiresolution model, Texture Mipmap Quadtree (TMQ), to represent large-scale textures. It facilitates fast loading and pre-filtering of textures from slower external storage. Integrating continuous LOD model of terrain geometry, we present a criterion to select proper textures from TMQ according to viewing parameters during rendering stage. By exploiting temporal coherence, a dynamic texture management scheme is devised based on two-level cache hierarchy to further increase the performance of texture mapping.

This study proposes a unified LZ and hybrid coding (ULHC) method for compound image and video compression of visually lossless quality and high compression ratio. The method is macroblock‐based for ultra‐low coding latency and compatibility with the conventional and most popular hybrid video coding standards such as H.264 and MPEG‐2. First, each macroblock is coded by two tools: (i) gzip, a popular lossless LZ coding tool, modified to be macroblock‐oriented and to be seamlessly unifiable with a lossy hybrid coding tool; (ii) H.264, an advanced lossy hybrid coding tool. Then rate‐distortion optimisation is used to select either the modified gzip or H.264 as the final coding. To seamlessly unify these two coding tools for maximum quality and high compression ratio in ULHC, the modified gzip uses the most recent reconstructed and specially serialised macroblock data as the dictionary. Experimental results show that for images and videos composed of natural or synthesised picture, text and graphics, the proposed method provides higher peak signal‐to‐noise ratio and better subjective quality than H.264 at the same bitrate, and also achieves much higher compression ratio than gzip without any visual quality loss. In fact, ULHC can achieve partial‐lossless and partial‐near‐lossless coding with a high compression ratio.

To evaluate the clinical impact and possible causes of a spontaneous decentration of a phakic refractive lens (PRL) implanted in a highly myopic eye, and analyzing the visual, refractive, and aberrometric outcome as well as the possible causes for this phenomenon. The description of a case of bilateral high myopia corrected by implantation with the phakic intraocular lens (pIOL) PRL (Carl Zeiss Meditec, Germany) is presented and documented. Both eyes had similar anatomical configuration, and therefore, a pIOL (Model 101) with the same size was implanted without any associated intraoperative complication. Clinical outcomes were evaluated during a 3-month follow-up. Implanted pIOLs were properly positioned in both eyes and provided an excellent visual outcome during the immediate postoperative period. However, 1 month after surgery, the patient presented a logarithm of the minimum angle of resolution uncorrected distance visual acuity of 0.15 and 0 in the OD and OS, respectively. Subjective refraction in the OD was +1.00 to 1.00 × 15°, with logarithm of the minimum angle of resolution corrected distance visual acuity of 0. Temporal displacement of the PRL was evident in the biomicroscopic examination and analyzed in detail with advanced imaging techniques finding an asymmetric vault. Regarding aberrometry, larger amounts of primary coma, and spherical aberration were present in the OS. Two months later, the situation remained stable. Spontaneous PRL decentration is not necessarily associated with a visual quality loss and a bad selection of pIOL size. For implantation of this pIOL, a comprehensive analysis of the zonule would be necessary.

Video-based free-viewpoint rendering from multiple view video capture has achieved video-realistic performance replay. Existing free-viewpoint rendering approaches require storage, streaming and re-sampling of multiple videos, which requires high bandwidth and computational resources limiting applications to local replay on high-performance computers. This paper introduces a layered texture representation for efficient storage and view-dependent rendering from multiple view video capture whilst maintaining the video-realism. Layered textures re-sample the captured video according to the surface visibility. Prioritisation of layers according to surface visibility allows the N-best views for all surface elements to be pre-computed significantly reducing both storage and rendering cost. Typically 3 texture map layers are required for free-viewpoint rendering with an equivalent visual quality to the multiple view video giving a significant reduction in storage cost. Quantitative evaluation demonstrates that the layered representation achieves a 90% reduction in storage cost and 50% reduction in rendering cost without loss of visual quality compared to storing only the foreground of the original multiple view video. This reduces the storage and transmission cost for free-viewpoint video rendering from eight cameras to be similar to the requirements for a single video. Streaming the layered representation enables, for the first time, demonstration of free-viewpoint video rendering on mobile devices and web platforms.