Facsimile and static presentation processing – Natural color facsimile – Color photography previewer
Reexamination Certificate
1998-05-15
2001-03-20
Coles, Edward L. (Department: 2722)
Facsimile and static presentation processing
Natural color facsimile
Color photography previewer
C358S506000, C358S518000, C358S523000, C382S167000
Reexamination Certificate
active
06204940
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to digital image processing and, more particularly, to processing scanned negative films.
2. Description of the Related Art
Systems are known in the art which can scan photos, negatives, and slides into a PC so that the images can be displayed or printed. For example, one such system is the HP PhotoSmart system (Hewlett-Packard Company, Palo Alto, Calif.) which includes the HP PhotoSmart Photo Scanner (part number C5100A) and the HP PhotoSmart Photo Printer (part number C3804A). The photo scanner is a quick and easy way to convert not only existing photographs, but also slides and negatives, to digital images. An operator merely inserts a photo, slide, or negative and the photo scanner automatically launches its software and displays a preview scan on the PC screen. Based on the finished photo size, the photo scanner's software chooses the optimum scanning resolution that will give professional photographic results and keep file size to a minimum.
In traditional analog photofinishing, a number of techniques have been developed by companies such as Kodak and Fuji to process color negatives. Some of the color balancing algorithms adjust image colors based on user preferences rather than actual scene colors. Also, some techniques try to determine the primary scene illuminant using a special sensor. The color images can then be color balanced based on this determination. Other systems rely on user intervention to correctly process the negatives.
Many digital film scanning systems used techniques based on those first developed for analog processing. However, these systems are often less robust than the analog systems they replace, because they attempt to operate without user intervention. Also, they cannot directly sense the film type automatically like the analog systems can. In fact, many digital film scanners give the best results if the user first enters the film type. This requires considerable expertise on the part of the user, and also typically requires a computer interface for enterring the information, so the scanner cannot easily be a standalone device.
Thus, although the scanning software can convert scanned negative film images to positive digital images, current state-of-the-art software is not as robust or easy to use as desired. Moreover, in order to calculate the positive digital image, such software often includes complex, time-consuming calculations.
Thus, it can be seen that current methods of digitally processing scanned negative films impose output speed and image fidelity limits upon image output devices, and hinder the use of these devices in many applications.
Therefore, there is an unresolved need for a technique that can improve the digital processing of scanned negative films by reducing the amount of time necessary to perform the process and by increasing the robustness and quality of the images produced.
SUMMARY OF THE INVENTION
A process and apparatus is described to improve the digital processing of scanned negative films by reducing the amount of time necessary to perform the process and by increasing the robustness and quality of the images produced. These benefits are achieved by a process of color inversion, white point and black point mapping, and midtone adjustment. White and black mapping increases the dynamic range of the image, as well as removes the color cast of the negative film. The black and white point mapping can result in a dark image when light sources, such as lit candles or incandescent bulbs, are visible in the scene. For one embidoment, a backlit image postprocessing algorithm is employed which uses heuristics to identify these situations, which are then brightened using a nonlinear power mapping.
For one embodiment, midtone adjustment includes the sub-steps of contrast reduction and color adjustment. Contrast reduction reverses the film exposure characteristics. Color adjustment removes the remaining color cast in the midtone region of the image, and obtains the correct brightness.
To summarize, starting from images with poor contrast and color cast, the system automatically looks for the appropriate correction parameters to produce images with vivid color and good contrast. This is achieved without rescanning or retaking the picture. The implementation, using one dimensional look-up-tables, is very efficient.
REFERENCES:
patent: 5329383 (1994-07-01), Collette
patent: 5447811 (1995-09-01), Buhr et al.
patent: 5499044 (1996-03-01), Collette
patent: 5724456 (1998-03-01), Boyack et al.
patent: 5781315 (1998-07-01), Yamaguchi
patent: 5956044 (1999-09-01), Giorgianni et al.
patent: 5978106 (1999-11-01), Hayashi
Lin Qian
Rix Malcolm
Stokes Michael
Tretter Daniel R.
Coles Edward L.
Hewlett--Packard Company
Wallerson Mark
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