Resampling

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# Resampling - PowerPoint PPT Presentation

Resampling. MALTAB. improfile(f,[XFP x],[YFP y],search_radius,\' bicubic \'); f ：原圖 [ ] ：座標 search_radius ：點數 bicubic ：函式. 各方法簡介 - 雙線性內插法. 雙線性內插法 (bilinear interpolation) 實際上為連續記算三次線性內插的結果 與最近相鄰內插法一樣，利用相鄰四點求取新的像素值 下頁式子中的 α 、 β 為點 p 對應鄰近四點的相對水平與垂直距離 假設點與點間距離為 1 ， 故 0 &lt; α 、 β &lt; 1. 3.

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## PowerPoint Slideshow about ' Resampling' - lali

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Presentation Transcript

### Resampling

MALTAB
• f：原圖
• [ ] ：座標
• bicubic：函式

• 雙線性內插法(bilinear interpolation)
• 實際上為連續記算三次線性內插的結果
• 與最近相鄰內插法一樣，利用相鄰四點求取新的像素值
• 下頁式子中的α、β為點p對應鄰近四點的相對水平與垂直距離
• 假設點與點間距離為1 ， 故 0 < α、β < 1

3

• 作法
• 第一次線性內插
• 即a 、b兩點對p的影響，可求出e點像素
• 第二次線性內插
• 即c 、d兩點對p的影響，可求出f點像素
• 最後對e 、f兩點做內插

4

C / C++
• //計算bilinear需要的alpha,beta值
• alpha = point_x - prepoint_x ;
• beta = 1 - ( point_y - prepoint_y ) ;
• //start bilinear interpolation
• gray_a = ( 1 - alpha ) * *( pImage + 8 * ( prepoint_x ) + ( prepoint_y + 1 ) ) + alpha * *( pImage + 8 * ( prepoint_x + 1 ) + ( prepoint_y + 1 ) ) ;
• gray_b = ( 1 - alpha ) * *( pImage + 8 * ( prepoint_x ) + ( prepoint_y ) ) + alpha * *( pImage + 8 * ( prepoint_x + 1 ) + ( prepoint_y ) ) ;
• last_gray = ( 1 - beta ) * gray_a + beta * gray_b ;
• gray_value[ count1++ ] = ( int )last_gray ;