Research Themes

Laboratory of Mathematical Science for Computing

Themes

Techniques for Restoring Faded Color Photographs

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Since being introduced in the early 1900s, color photographs based on silver halides serve an important role in preserving historic information for future generations.  However, many of these photographs are fading and deteriorating as they continue to age.  The deterioration of a color film depends on factors including the storage environment and the age of the film, so it is generally not sufficient to simply apply a uniform, automatic procedure to recover the original image.  Additionally, it was not clear if true restoration is even possible.  Our laboratory was approached by iword, a Sapporo-based company interested in resolving this problem, to jointly develop techniques and software for restoring faded color photographs.

Many faded photographs contain an area where we can guess the original color, such as the sky, clouds or grass.  We can begin by restoring these areas to their original color.  However, there are infinitely many models that accomplish this restoration, and we wish to choose a simple model that effectively restores the image.  In our joint research, we were fortunate to obtain for several images both the faded color film and prints that had been made before the image had heavily faded.  By analyzing these images, we were able to determine that affine transformations can effectively map the faded colors (as vectors of primary colors) to their restored colors.  This method requires four points where the original and faded colors are known, in order to completely restore the original image.

The attached image shows an image obtained from 60-year old original, faded film on the left, and the restored version produced with our techniques on the right. (The original faded film is provided by Ancient Orient Museum, Tokyo.)

Faculty

Akira Tanaka
Akira Tanaka
Position
Professor
Specialized field
Image and acoustic signal processing, fundamental learning theory
Hobby
Musical appreciation and performance, driving, drinking

I feel that recent students tend to downplay the importance of the theoretical aspects of researches. I think it is crucial to clarify what is guaranteed. In your student days, please find at least one theoretically firm knowledge.

Mayuka F. Kawaguchi
Mayuka F. Kawaguchi
Position
Associate Professor
Specialized field
Fuzzy theory, multiple-valued logic
Hobby
Making preserved foods (basil paste, pickles, jam, etc) and consuming them

Participate proactively to lectures, exercises, experiments provided in our course, not passively. Any proactive approach should give you a clue to find out your research theme. Also, the basic knowledge and learning techniques should be assets through your life as any specialist. I’m looking forward to being inspired by you own unique challenges.