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sparse image representation via combined transforms - Convex ...

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2.3 Discussion..................................... 21<br />

2.4 Proof........................................ 22<br />

3 Image Transforms and Image Features 25<br />

3.1 DCT and Homogeneous Components ...................... 28<br />

3.1.1 Discrete Fourier Transform . ...................... 28<br />

3.1.2 Discrete Cosine Transform . . ...................... 38<br />

3.1.3 Discrete Sine Transform . . . ...................... 43<br />

3.1.4 Homogeneous Components . ...................... 44<br />

3.1.5 2-DDCT ................................. 52<br />

3.2 Wavelets and Point Singularities . . ...................... 52<br />

3.2.1 MultiresolutionAnalysis......................... 54<br />

3.2.2 FilterBanks ............................... 57<br />

3.2.3 Discrete Algorithm . . .......................... 58<br />

3.2.4 PointSingularities ............................ 60<br />

3.3 Edgelets and Linear Singularities . . ...................... 64<br />

3.3.1 Edgelet System .............................. 64<br />

3.3.2 Edgelet Transform . . .......................... 64<br />

3.3.3 Edgelet Features . . . .......................... 65<br />

3.3.4 Fast Approximate Edgelet Transform . . . .............. 65<br />

3.4 OtherTransforms................................. 66<br />

3.4.1 Transformsfor1-DSignals ....................... 66<br />

3.4.2 Transforms for 2-D Images . ...................... 73<br />

3.5 Discussion..................................... 74<br />

3.6 Conclusion .................................... 76<br />

3.7 Proofs ....................................... 76<br />

4 Combined Image Representation 81<br />

4.1 Why Combined Image Representation? . . . .................. 81<br />

4.2 SparseDecomposition .............................. 83<br />

4.3 Minimum l 1 NormSolution ........................... 84<br />

4.4 Lagrange Multipliers . .............................. 86<br />

4.5 How to Choose ρ and λ ............................. 88<br />

4.6 Homotopy ..................................... 91<br />

xiv

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