Leica Geosystems’ ImageEqualizer Eliminates Flaws 05.01.2002
Even with the best satellite sensors, aerial cameras and scanners available today, digital photogrammetry professionals must contend with imperfections inherent in imagery acquired in varying conditions. Thanks to ImageEqualizer, these imagery problems can be easily resolved. New from Leica Geosystems’ GIS & Mapping Division, ImageEqualizer is a standalone application for correcting image variations such as hot spots, unequal lighting, atmospheric and temporal effects, or color cast, in single and multiple images simultaneously. ImageEqualizer features an intuitive, real-time graphical interface, which allows users to define optimal correction parameters quickly, saving valuable time and effort.
Owing to the nature of camera lenses, weather conditions, sun angle, seasonal variations, different film types and processing, obtaining consistent radiometric content across large areas is difficult. Although some variations in image quality can be remedied during scanning, most scanned imagery requires further manipulation and correction prior to use for photogrammetric applications. This is especially true for mosaicking projects, which demand a smooth transition and homogenous balance of color and contrast between many independent images.
Once the user selects the image or images to be corrected, ImageEqualizer sections the imagery into tiles of selectable size and collects statistical information about the brightness and contrast for each color band per tile. The program then uses this information to create a correction function, the parameters of which can be manipulated to compensate for disproportionate variations in color and contrast for each image. The user-friendly interface gives the operator complete control over the settings and constraints for each color band. The program's instantaneous preview window displays the images with the original and modified settings side-by-side for easy and quick evaluation of the optimal parameters towards which the images need to converge. The chosen settings can then be applied to one or more images.
ImageEqualizer is the only standalone, user-friendly image correcting software tailored to fit photogrammetrists' needs that offers real-time, graphical preview and is able to correct for several imperfections within a single image. Particularly helpful in preparing frame imagery for mosaicking, ImageEqualizer can quickly compensate for imagery defects by applying chosen brightness and contrast parameters for each color band in a smooth, piecewise fashion to multiple images in the same project. Alternatively, ImageEqualizer can drive all images towards the parameters of a single image in the project. The preview functionality is also useful for quality control and review of large batches of imagery simultaneously. For further convenience and efficiency, ImageEqualizer is fully multithreaded and multiprocessor-enabled, ensuring the highest computer throughput and utilization. Extremely customizable and versatile, ImageEqualizer also allows the user to arrange the layout of the application windows for the preferred size, resolution and location of the displayed imagery. The viewing windows’ settings for percent overlap, strip layout, and cropping percentage provide the user with an instantaneous mosaic view of the balanced or raw imagery.
Although experience and training are important when it comes to photogrammetric applications, it doesn't take an expert to use ImageEqualizer. The program is extremely easy to learn and use and comes with a built-in, interactive help guide. ImageEqualizer can run on a Windows or Unix platform and recognizes a wide variety of image file types. Specialists using large digital files of imagery for applications where the visual appearance of the imagery is important will find ImageEqualizer to be an invaluable tool.