The.Algorithm.Design.Manual.Springer-Verlag.1998

War Story: Evolution of the Lobster
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Programming
War Story: Evolution of the Lobster
I'll confess that I'm always surprised to see graduate students stop by my office early in the morning.
Something about working through the night makes that time inconvenient for them. But there they were,
two future Ph.D.s working in the field of high-performance computer graphics. They studied new
techniques for rendering pretty computer images. The picture they painted for me that morning was
anything but pretty, however.
``You see, we want to build a program to morph one image into another,'' they explained.
``What do you mean by morph?'' I asked.
``For special effects in movies, we want to construct the intermediate stages in transforming one image
into another. Suppose we want to turn you into Humphrey Bogart. For this to look realistic, we must
construct a bunch of in-between frames that start out looking like you and end up looking like him.''
``If you can realistically turn me into Bogart, you have something,'' I agreed.
``But our problem is that it isn't very realistic.'' They showed me a dismal morph between two images.
``The trouble is that we must find the right correspondence between features in the two images. It looks
real bad when we get the correspondence wrong and try to morph a lip into an ear.''
``I'll bet. So you want me to give you an algorithm for matching up lips?''
Figure: A successful alignment of two lines of pixels
``No, even simpler. We just morph each row of the initial image into the identical row of the final image.
You can assume that we give you two lines of pixels, and you have to find the best possible match
between the dark pixels in a row from object A to the dark pixels in the corresponding row of object B.
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