Resampling
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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 < α 、 β < 1. 3.

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Resampling

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Resampling

Resampling


Maltab

MALTAB

  • improfile(f,[XFP x],[YFP y],search_radius,'bicubic');

    • f:原圖

    • [ ] :座標

    • search_radius :點數

    • bicubic:函式


Resampling

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 < α、β < 1

3


Resampling

各方法簡介-雙線性內插法

  • 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

      可求得p點像素

4


Resampling

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 ;


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