具有聚類(lèi)結(jié)構(gòu)相似性的非參數(shù)貝葉斯字典學(xué)習(xí)算法
doi: 10.11999/JEIT190496 cstr: 32379.14.JEIT190496
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海軍航空大學(xué)信號(hào)與信息處理山東省重點(diǎn)實(shí)驗(yàn)室 煙臺(tái) 264001
A Nonparametric Bayesian Dictionary Learning Algorithm with Clustering Structure Similarity
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Signal and Information Processing Key Laboratory in Shandong, Navy Aviation University, Yantai 264001, China
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摘要: 利用圖像結(jié)構(gòu)信息是字典學(xué)習(xí)的難點(diǎn),針對(duì)傳統(tǒng)非參數(shù)貝葉斯算法對(duì)圖像結(jié)構(gòu)信息利用不充分,以及算法運(yùn)行效率低下的問(wèn)題,該文提出一種結(jié)構(gòu)相似性聚類(lèi)beta過(guò)程因子分析(SSC-BPFA)字典學(xué)習(xí)算法。該算法通過(guò)Markov隨機(jī)場(chǎng)和分層Dirichlet過(guò)程實(shí)現(xiàn)對(duì)圖像局部結(jié)構(gòu)相似性和全局聚類(lèi)差異性的兼顧,利用變分貝葉斯推斷完成對(duì)概率模型的高效學(xué)習(xí),在確保算法收斂性的同時(shí)具有聚類(lèi)的自適應(yīng)性。實(shí)驗(yàn)表明,相比目前非參數(shù)貝葉斯字典學(xué)習(xí)方面的主流算法,該文算法在圖像去噪和插值修復(fù)應(yīng)用中具有更高的表示精度、結(jié)構(gòu)相似性測(cè)度和運(yùn)行效率。
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關(guān)鍵詞:
- 變分貝葉斯 /
- Markov隨機(jī)場(chǎng) /
- 字典學(xué)習(xí) /
- 去噪 /
- 修復(fù)
Abstract: Making use of image structure information is a difficult problem in dictionary learning, the traditional nonparametric Bayesian algorithms lack the ability to make full use of image structure information, and faces problem of inefficiency. To this end, a dictionary learning algorithm called Structure Similarity Clustering-Beta Process Factor Analysis (SSC-BPFA) is proposed in this paper, which completes efficient learning of the probabilistic model via variational Bayesian inference and ensures the convergence and self-adaptability of the algorithm. Image denoising and inpainting experiments show that this algorithm has significant advantages in representation accuracy, structure similarity index and running efficiency compared with the existing nonparametric Bayesian dictionary learning algorithms.-
Key words:
- Variational Bayesian /
- Markov Random Field (MRF) /
- Dictionary Learning (DL) /
- Denoising /
- Inpainting
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表 1 模型中隱變量及其變分參數(shù)的VB推斷更新公式
隱變量 變分分布 變分參數(shù)的VB推斷更新公式 隱變量更新公式 ${{q7j3ldu95}_k}$ $q\left( {{{q7j3ldu95}_k}} \right) \propto {\rm{Normal}}\left( {{{q7j3ldu95}_k}|{{{\tilde { m}}}_k},{{{\tilde { \Lambda }}}_k}} \right)$ ${ {\tilde{ \varLambda } }_k} = P{ {{I} }_P} + \displaystyle\sum\nolimits_{i = 1}^N {\dfrac{ { { {\tilde e}_0} } }{ { { {\tilde f}_0} } }\left( {\tilde \mu _{ik}^2 + \tilde \sigma _{ik}^2} \right){ {\tilde \rho }_{ik} }{ {{I} }_P} }$,
${ {\tilde { m} }_k} = {\tilde { \varLambda } }_k^{ - 1} \cdot \left( {\displaystyle\sum\nolimits_{i = 1}^N {\dfrac{ { { {\tilde e}_0} } }{ { { {\tilde f}_0} } }{ {\tilde \mu }_{ik} }{ {\tilde \rho }_{ik} }{{x} }_i^{ - k} } } \right)$${{q7j3ldu95}_k} = {{\tilde { m}}_k}$ ${s_{ik}}$ $q\left( {{s_{ik}}} \right) \propto {\rm{Normal}}\left( {{s_{ik}}|{{\tilde \mu }_{ik}},\tilde \sigma _{ik}^2} \right)$ $\tilde \sigma _{ik}^2 = {\left\{ {\dfrac{ { { {\tilde e}_0} } }{ { { {\tilde f}_0} } }{ {\tilde \rho }_{ik} }\left[ { {\tilde { m} }_k^{\rm{T} }{ { {\tilde { m} } }_k} + {\rm{tr(} }{\tilde { \varLambda } }_k^{ - 1}{\rm{)} } } \right] + \dfrac{ { { {\tilde c}_0} } }{ { { {\tilde f}_0} } } } \right\}^{ - 1} }$,
${\tilde \mu _{ik}} = \tilde \sigma _{ik}^2 \cdot \left( {\dfrac{{{{\tilde e}_0}}}{{{{\tilde f}_0}}}{{\tilde \rho }_{ik}}{\tilde { m}}_k^{\rm{T}}{{x}}_i^{ - k}} \right)$${s_{ik}} = {\tilde \mu _{ik}}$ ${z_{ik}}$ $q\left( {{z_{ik}}} \right) \propto {\rm{Bernoulli}}\left( {{z_{ik}}|{{\tilde \rho }_{ik}}} \right)$ ${\tilde \rho _{ik}} = \dfrac{{{\rho _{ik,1}}}}{{{\rho _{ik,1}} + {\rho _{ik,0}}}}$,
${\rho _{ik,0}} = \exp \left\{ \displaystyle\sum\nolimits_{l = 1}^L {{{\tilde \xi }_{il}} \cdot [\psi ({{\tilde b}_{lk}}) - \psi ({{\tilde a}_{lk}} + {{\tilde b}_{lk}})]} \right\} $$\begin{array}{l} {\rho _{ik,1} } = \exp \Bigr\{ - \dfrac{1}{2}\dfrac{ { { {\tilde e}_0} } }{ { { {\tilde f}_0} } }(\tilde \mu _{ik}^2 + \tilde \sigma _{ik}^2)({\tilde { m} }_k^{\rm{T} }{ { {\tilde { m} } }_k} + {\rm{tr} }({\tilde { \varLambda } }_k^{ - 1})) \\\qquad\quad\ + \dfrac{ { { {\tilde e}_0} } }{ { { {\tilde f}_0} } }{ {\tilde \mu }_{ik} }{\tilde { m} }_k^{\rm{T} }{{x} }_i^{ - k} + \displaystyle\sum\nolimits_{l = 1}^L { { {\tilde \xi }_{il} } \cdot [\psi ({ {\tilde a}_{lk} }) - \psi ({ {\tilde a}_{lk} } + { {\tilde b}_{lk} })]} \Bigr\} \end{array}$${z_{ik}} = {\tilde \rho _{ik}}$ $\pi _{lk}^ * $ $q\left( {\pi _{lk}^ * } \right) \propto {\rm{Beta}}\left( {\pi _{lk}^ * |{{\tilde a}_{lk}},{{\tilde b}_{lk}}} \right)$ ${\tilde a_{lk} } = { { {a_0} } / K} + \displaystyle\sum\nolimits_{i = 1}^N { { {\tilde \rho }_{ik} }{ {\tilde \xi }_{il} } }$, ${\tilde b_{lk}} = {{{b_0}(K - 1)} / K} + \displaystyle\sum\nolimits_{i = 1}^N {(1 - {{\tilde \rho }_{ik}}){{\tilde \xi }_{il}}} $ $\pi _{lk}^ * = \dfrac{{{{\tilde a}_{lk}}}}{{{{\tilde a}_{lk}} + {{\tilde b}_{lk}}}}$ ${t_i}$ $q\left( { {t_i} } \right) \propto {\rm{Multi} }\left( { { {\tilde \xi }_{i1} },{ {\tilde \xi }_{i2} },···,{ {\tilde \xi }_{iL} } } \right)$ ${\tilde \xi _{il}} = {{{\xi _{il}}} / {\displaystyle\sum\nolimits_{l' = 1}^L {{\xi _{il'}}} }}$,
$\begin{array}{l} {\xi _{il} } = \exp \Bigr\{ \displaystyle\sum\nolimits_{k = 1}^K { { {\tilde \rho }_{ik} }[\psi ({ {\tilde a}_{lk} }) - \psi ({ {\tilde a}_{lk} } + { {\tilde b}_{lk} })]} \\ \qquad\quad + \displaystyle\sum\nolimits_{k = 1}^K {(1 - { {\tilde \rho }_{ik} })[\psi ({ {\tilde b}_{lk} }) - \psi \left({ {\tilde a}_{lk} } + { {\tilde b}_{lk} }\right)]} \\ \qquad\quad + \psi ({ {\tilde \zeta }_{il} }) - \psi \left(\displaystyle\sum\nolimits_{l' = 1}^L { { {\tilde \zeta }_{il'} } } \right)\Bigr\} \\ \end{array}$${t_i} = \mathop {\arg \max }\limits_l \left\{ {{{\tilde \xi }_{il}},_{}^{}\forall l \in [1,L]} \right\}$ ${\beta _{il}}$ $q\left( {\{ {\beta _{il} }\} _{l = 1}^L} \right) \propto {\rm{Diri} }\left( { { {\tilde \lambda }_{i1} },{ {\tilde \lambda }_{i2} },···,{ {\tilde \lambda }_{iL} } } \right)$ ${\tilde \lambda _{il}} = {\tilde \xi _{il}} + {\alpha _0}{G_{il}}$ ${\beta _{il}} = {{{{\tilde \lambda }_{il}}} / {\displaystyle\sum\nolimits_{l' = 1}^L {{{\tilde \lambda }_{il'}}} }}$ ${\gamma _s}$ $q\left( {{\gamma _s}} \right) \propto {\rm{Gamma}}\left( {{\gamma _s}|{{\tilde c}_0},{{\tilde d}_0}} \right)$ ${\tilde c_0} = {c_0} + \dfrac{1}{2}NK$, ${\tilde d_0} = {d_0} + \dfrac{1}{2}\displaystyle\sum\nolimits_{i = 1}^N {\displaystyle\sum\nolimits_{k = 1}^K {\left( {\tilde \mu _{ik}^2 + \tilde \sigma _{ik}^2} \right)} } $ ${\gamma _s} = {{{{\tilde c}_0}} / {{{\tilde d}_0}}}$ ${\gamma _\varepsilon }$ $q\left( {{\gamma _\varepsilon }} \right) \propto {\rm{Gamma}}\left( {{\gamma _\varepsilon }|{{\tilde e}_0},{{\tilde f}_0}} \right)$ ${\tilde e_0} = {e_0} + \dfrac{1}{2}NP$, ${\tilde f_0} = {f_0} + \dfrac{1}{2}\displaystyle\sum\nolimits_{i = 1}^N {\left\| {{{{x}}_i} - {\hat{ D}}\left( {{{{\hat{ s}}}_i} \odot {{{\hat{ z}}}_i}} \right)} \right\|} $ ${\gamma _\varepsilon } = {{{{\tilde e}_0}} / {{{\tilde f}_0}}}$ 算法1 SSC-BPFA算法 輸入:訓(xùn)練數(shù)據(jù)樣本集$\left\{ {{{{x}}_i}} \right\}_{i = 1}^N$ 輸出:字典${{D}}$、權(quán)重$\left\{ {{{{s}}_i}} \right\}_{i = 1}^N$、稀疏模式指示向量$\left\{ {{{{z}}_i}} \right\}_{i = 1}^N$及聚類(lèi)標(biāo)簽$\left\{ {{t_i}} \right\}_{i = 1}^N$ 步驟 1 設(shè)置收斂閾值$\tau $和迭代次數(shù)上限${\rm{it}}{{\rm{r}}_{\max }}$,初始化原子數(shù)目$K$與聚類(lèi)數(shù)目$L$,通過(guò)K-均值算法對(duì)數(shù)據(jù)樣本進(jìn)行初始聚類(lèi); 步驟 2 按照式(1)—式(15)完成NPB-DL的概率建模; 步驟 3 初始化隱變量集${{\varTheta } }$和變分參數(shù)集${{{ H}}}$,計(jì)算${\hat{ X}} = {{D}}\left( {{{S}} \odot {{Z}}} \right)$,令迭代索引${\rm{itr}}$=1; 步驟 4 按照表1的VB推斷公式對(duì)${{\varTheta } }$和${{{ H}}}$進(jìn)行更新,計(jì)算${{\hat{ X}}^{{\rm{new}}}} = {{D}}\left( {{{S}} \odot {{Z}}} \right)$;
步驟 5 令${\rm{itr}}$值增加1,刪除${{D}}$中未使用的原子并更新$K$的值,計(jì)算$r = {{\left\| {{{{\hat{ X}}}^{{\rm{new}}}} - {\hat{ X}}} \right\|_{\rm{F}}^2} / {\left\| {{\hat{ X}}} \right\|_{\rm{F}}^2}}$,若$r < \tau $或${\rm{itr}} \ge {\rm{it}}{{\rm{r}}_{\max }}$,刪除所含樣本
占全部樣本數(shù)量比例低于${10^{ - 3}}$的聚類(lèi),將被刪聚類(lèi)內(nèi)的樣本分配到剩余聚類(lèi)中${\tilde \xi _{il}}$最大的那個(gè)聚類(lèi)中,進(jìn)入步驟6,否則跳回步驟4;步驟 6 固定${t_i}$和${\beta _{il}}$及其變分參數(shù)的估計(jì)結(jié)果,將${{q7j3ldu95}_k}$, ${s_{ik}}$, ${z_{ik}}$, $\pi _{lk}^ * $, ${\gamma _s}$和${\gamma _\varepsilon }$這6個(gè)隱變量及其對(duì)應(yīng)的變分參數(shù)繼續(xù)進(jìn)行迭代優(yōu)化更新,直至
重新達(dá)到收斂.下載: 導(dǎo)出CSV
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