April 2014
Beginner to intermediate
830 pages
15h 21m
Chinese
Content preview from Mathematica 錦囊妙計
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352
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第八章
不連續區域的效應較明顯，而對變化緩慢的區域則影響不大。從以下範例中可觀察到這
一點，將輸入圖形進行反向的拉普拉斯算符。
圖 8-2 摺積核心
[Page-355]
ch08.indd 352 2014/4/2 下午 12:24:00
8.6 使用傅立葉轉換實作影像清晰化及模糊化
|
353
延伸資訊
Mathematica 7 開始提供內建
Sharpen
指令進行影像清晰化（
http://bit.ly/2rutpn
）。
8.6 使用傅立葉轉換實作影像清晰化及模糊化
問題點
你想加強影像的低頻或高頻特性。[Page-356]
解決方案
內建的
Fourier
指令可直接進行高品質的
快速傅立葉轉換
（
Fast Fourier Transform
，
FFT），因此傅立葉轉換影像處理在 Mathematica 中特別簡單。傅立葉影像處理的步驟
如下：
1. 計算圖形的傅立葉轉換。
2. 集中化（centering）傅立葉轉換，方法請見後文「討論說明」部分。
3. 作用濾波函數於轉換結果。
4. 恢復集中化。
5. 進行反傅立葉轉換，並忽略虛部。
集中化轉換
ch08.indd 353 2014/4/2 下午 12:24:01
354
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第八章
以上建立的
fourierFilter
函數可使用自訂的濾波函數，以下提供幾
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