双线性插值算法推导及代码实现

来源：互联网发布：数组可以不指定长度吗编辑：程序博客网时间：2024/06/06 19:23

双线性插值，是一种比较重要的插值方法，尤其在数字图像处理领域。本篇博文分为三个部分：一是双线性插值的算法推导，二是双线性插值的算法实现，三是算法的运行结果。

一双线性插值的算法推导

二代码实现（matlab）

function [out] = bilinearInterpolation(im, out_dims)    in_rows = size(im,1);    in_cols = size(im,2);    out_rows = out_dims(1);    out_cols = out_dims(2);    S_R = in_rows / out_rows;    S_C = in_cols / out_cols;    [cf, rf] = meshgrid(1 : out_cols, 1 : out_rows);    rf = rf * S_R;    cf = cf * S_C;    r = floor(rf);    c = floor(cf);    r(r < 1) = 1;    c(c < 1) = 1;    r(r > in_rows - 1) = in_rows - 1;    c(c > in_cols - 1) = in_cols - 1;    delta_R = rf - r;    delta_C = cf - c;    in1_ind = sub2ind([in_rows, in_cols], r, c);    in2_ind = sub2ind([in_rows, in_cols], r+1,c);    in3_ind = sub2ind([in_rows, in_cols], r, c+1);    in4_ind = sub2ind([in_rows, in_cols], r+1, c+1);           out = zeros(out_rows, out_cols, size(im, 3));    out = cast(out, class(im));     for idx = 1 : size(im, 3)        chan = double(im(:,:,idx)); %// Get i'th channel        %// Interpolate the channel        tmp = chan(in1_ind).*(1 - delta_R).*(1 - delta_C) + ...                       chan(in2_ind).*(delta_R).*(1 - delta_C) + ...                       chan(in3_ind).*(1 - delta_R).*(delta_C) + ...                       chan(in4_ind).*(delta_R).*(delta_C);        out(:,:,idx) = cast(tmp, class(im));    end

三双线性插值运行结果

>>I = imread('lena.jpg');
>> figure,imshow(I)
>> S = bilinearInterpolation(I,[1000,1000]);
>> figure,imshow(S)

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