Embedded zerotrees of wavelet transforms: Difference between revisions

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=== A. Encoding a coefficient of the significance map ===

In a significance map, the coefficients can be representingrepresented by the following four different symbols. With using these symbols to represent the image information, the coding will be less complicationcomplicated.

==== 1. Zerotree root ====

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==== 2. Isolated zero ====

If the magnitude of a coefficient that is lesslower than a threshold T, but it still has some significant descendants, then this coefficient is called isolated zero.

==== 3. Positive significant coefficient ====

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=== B. Defining threshold ===

The threshold usingused above can be defined as the type belowfollows.

==== 1. Initial threshold T₀:, (Assumeassuming C_max is the largest coefficient.): ====

<span>[[File:Threshold-0119.png|126x126px]]</span>

==== 2. Threshold T_i is iteratively reduced to half of the value of the previous threshold.: ====

[[File:Threshold-01192.png|frameless|133x133px]]

==== 1. Initial threshold T₀: (Assume C_max is the largest coefficient.) ====

<span>[[File:Threshold-0119.png|126x126px]]</span>

==== 2. Threshold T_i is reduced to half of the value of the previous threshold. ====

[[File:Threshold-01192.png|frameless|133x133px]]

=== C. Scanning order for coefficients ===

'''[[Raster scanningscan]]''' is theused rectangularin patterna of image capture and reconstruction. Using this scanning on EZW transform is to perform scanning the coefficients inway such way that no childchildren nodenodes isare scanned before itstheir parent nodenodes. Also, all positionscoefficients in a given subband are scanned before itthose movesof to the next subband.

=== D. Two-pass bitplane coding ===

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[[Category:Image compression]]

[[Category:Trees (data structures)]]

[[Category:WaveletsLossy compression algorithms]]

[[Category:Data compression]]