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 dicult 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 rst 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 rst 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 eect when applied to small signals but compresses large signals to t within an asymptotic limit. We demonstrate the eectiveness of these approaches by comparing processed and unprocessed images.