Two Methods for Display of High Contrast Images

High contrast images are common in night scenes and other scenes that include dark shadows and bright light sources. These scenes are difficult to display because their contrasts greatly exceed the range of most display devices for images. As a result, the image contrasts are compressed or truncated, obscuring subtle textures and details. Humans view and understand high contrast scenes easily, ``adapting'' their visual response to avoid compression or truncation with no apparent loss of detail. By imitating some of these visual adaptation processes, we developed two methods for the improved display of high contrast images. The first builds a display image from several layers of lighting and surface properties. Only the lighting layers are compressed, drastically reducing contrast while preserving much of the image detail. This method is practical only for synthetic images where the layers can be retained from the rendering process. The second method interactively adjusts the displayed image to preserve local contrasts in a small ``foveal'' neighborhood. Unlike the first method, this technique is usable on any image and includes a new tone reproduction operator. Both methods use a sigmoid function for contrast compression. This function has no effect when applied to small signals but compresses large signals to fit within an asymptotic limit. We demonstrate the effectiveness of these approaches by comparing processed and unprocessed images

Three methods of detail-preserving contrast reduction for displayed images

Ph.D.Greg Tur

High Quality Image Warp Filters on Pyramids

Directional filters applied to prefiltered imput image pyramids strike a good balance between fast computation and sharp, alias-free images, and are widely used for texture mapping and image warping. However, most published methods use implicit conversions between discrete and continuous images. This causes two flaws: 1) an input reconstruction filter is missing, causing unpredictable warp-dependent distortions and aliasing artifacts, and 2) address calculations are needlessly complex and inflexible. By including this filter we find a simpler, more accurate, and more general implementation of filtering for texture maps and image warping that can use any desired filter kernel. Effects of cascaded filters in image pyramids are also briefly discussed

Tone Reproduction for Realistic Computer Generated Images

Radiosity and other global illumination methods for image synthesis calculate the 'real world' radiance values of a scene instead of the display radiance values that will represent them. This causes 'display range' problems that are often solved by ad-hoc means, giving little assurance that the evoked visual sensations (brightness, color, etc.) are truly equivalent. Workers in photography have studied such perception matching as 'tone reproduction', and devised correcting operators from both empirical and vision research data. Corrections are usually limited by the chemical/optical restrictions of film. These practical film methods were adopted by television systems and then by computer graphics, despite the ease of implementing better correction operators by computer. In this paper we advocate the use of better tone reproduction for computer graphics. We give a general framework for tone reproduction, where mathematical models of the display device and human observers define an explicit conversion from real-world to display device radiance. These are used to review tone reproduction operators used for film and television. A brief summary of some applicable vision research literature leads to a simple example of an improved operator. We apply the Stevens & Stevens models of brightness vs. luminance relations to our framework to create a new tone reproduction operator for black & white computer generated images. The new operator is shown to be a reasonable solution to the display range problem, and further extensions are suggested

Quadrature Prefiltering for High Quality Antialiasing

This paper describes an efficient and relatively simple new prefiltering algorithm called quadrature prefiltering. Quadrature prefiltering provides very high quality suppression of aliasing artifacts at reasonable cost for images which would require extremely high super sampling rates using either regular super sampling or stochastic sampling to obtain equivalent antialiasing performance and signal to noise ratio. The new algorithm allows arbitrary filter kernels including non-radially symmetric filter kernels while only requiring a two dimensional look up table. Previous algorithms have required a three dimensional lookup table or radially symmetric filter kernels. It is only slightly more complicated to implement than box prefiltering, a commonly used antialiasing prefilter, but it generates images with much less visible aliasing artifacts

Glyphmaker: An Interactive, Programmerless Approach for Customizing, Exploring, and Analyzing Visual Data Representations

Glyphmaker is an interactive system for data visualization and analysis that is built in a dataflow environment. Glyphmaker provides a quite general platform for user-defined visualizations, one that can be extended in many ways and that, in particular, offers the first stage for an integrated visualization/analysis system. It is well-suited for the exploration and analysis of multivariate, highly correlated 3D data, which is increasingly the form of modern data. This is both because of the glyph-based visual representations and the interactivity that are built into the system. To summarize its capabilities, Glyphmaker allows the user to: (a) design glyphs by assembling them from different shapes; (b) choose binding sites on these shapes; (c) bind user data attributes to glyph elements; (d) conditionally isolate certain variable ranges; (e) interactively view, explore, remove, or rebind the resulting glyph sets as solid 3D objects. Each of these capabilities has a graphical user interface and is built into Glyphmaker in a modular form. The Glyphmaker approach of arranging data into data objects that are then bound to 3D graphical objects (glyphs) or manipulated by interactive tools is quite extensible in terms of visual representations and analysis methods