您正在看的计算机英语是:计算机新词及其详解。

　　Wavelets

　　Definition: Wavelets are mathematical functions that let us divide data into different frequency components and then study each component with a resolution appropriate for its overall scale. Wavelets are used in computer imaging, animation, noise reduction and data compression.

　　In many fields of study, from science and engineering to economics and psychology, we need to analyze data so that we can discover underlying patterns and information. A common way of doing this is to transform the data by applying mathematical functions.

　　One of the best-known processing techniques is Fourier analysis, in which you can approximate a real-world data stream by adding together a series of sine and cosine curves at different frequencies; the more curves you include in your approximation, the more closely you can replicate the original data. Since we know how to work with these well-defined trigonometric curves, we can often deduce patterns in the data that would otherwise remain hidden.

　　But Fourier analysis has limitations. It works best when the original data has features that repeat periodically, and it has trouble with transient signals or data that shows abrupt changes, such as the spoken word. Often, we need to be able to change our analytical representation depending on the actual data, so that we can resolve more detail in specific parts of the data stream. In essence, we need a way to change scale at various points, and scale is at the heart of wavelets.

　　The following eXPlanation is adapted from Dana Mackenzie’s highly recommended article “Wavelets: Seeing the Forest and the Trees” .

　　Consider how we view a landscape. If you’re looking down from a jet airliner in summer, a forest appears as a solid canopy of green. If you’re in a car driving by, however, you see individual trees. If you stop and move closer, you can make out individual branches and leaves. Up close, you may spot a dewdrop or an insect sitting on a leaf. With a magnifying glass, you can see structural details of the leaf and its veins.

　　As we get ever closer to an object, our view becomes narrower and we see finer and finer detail. In other words, as our scope becomes smaller, our resolution becomes greater.

　　Our eyes and mind adapt quickly to these changes in perspective, moving from the macro scale to the micro. Unfortunately, we can’t apply this technique to a photograph or computerized digital image.

　　If you enlarged a picture of a forest (as if you were trying to get