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Definition of a lens

Lenses

A lens is a custom view of the content in the repository. You can think of it as a fancy kind of list that will let you see content through the eyes of organizations and people you trust.

What is in a lens?

Lens makers point to materials (modules and collections), creating a guide that includes their own comments and descriptive tags about the content.

Who can create a lens?

Any individual member, a community, or a respected organization.

What are tags?

Tags are descriptors added by lens makers to help label content, attaching a vocabulary that is meaningful in the context of the lens.

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• eScience, eResearch and Computational Problem Solving

This module is included inLens: eScience, eResearch and Computational Problem Solving
By: Jan E. OdegardAs a part of collection: "Image Coding"

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Wavelets

Module by: Nick Kingsbury. E-mail the author

Summary: This module introduces the wavelets.

The process of creating the outputs y1 y1 to y0000 y0000 from xx is known as the discrete wavelet transform (DWT); and the reconstruction process is the inverse DWT.

The word wavelet refers to the impulse response of the cascade of filters which leads to a given bandpass output. The frequency response of the wavelet at level kk is obtained by substituting z=eiω Ts z ω Ts in the z-transfer function H k , 1 H k , 1 from this equation and this equation from our discussion of the binary filter tree. Ts Ts is the sampling period at the input to the filter tree.

Since the frequency responses of the bandpass bands are scaled down by 2:1 at each level, their impulse responses become longer by the same factor at each level, BUT their shapes remain very similar. The basic impulse response wave shape is almost independent of scale and known as the mother wavelet.

The impulse response to a lowpass output H k , 0 H k , 0 is called the scaling function at level kk.

Figure 1 shows these effects using the impulse responses and frequency responses for the five outputs of the 4-level tree of Haar filters, based on the z-transforms given in this group of equations. Notice the abrupt transitions in the middle and at the ends of the Haar wavelets. These result in noticeable blocking artefacts in decompressed images (as in part (b) of this previous figure).

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PDF | EPUB (?)

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My Favorites (?)

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Definition of a lens

Lenses

A lens is a custom view of the content in the repository. You can think of it as a fancy kind of list that will let you see content through the eyes of organizations and people you trust.

What is in a lens?

Lens makers point to materials (modules and collections), creating a guide that includes their own comments and descriptive tags about the content.

Who can create a lens?

Any individual member, a community, or a respected organization.

What are tags?

Tags are descriptors added by lens makers to help label content, attaching a vocabulary that is meaningful in the context of the lens.

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