Lanczos3算法在matlab中的实现方法

Lanczos插值算法简介：

Lanczos插值算法是一种高质量的图像插值方法。其利用一定数量的窗口像素计算出预测像素，用于生成更高分辨率的图像。

Lanczos3算法在matlab中的实现方法：

首先，我们需要在matlab中定义一个函数，包含双线性插值和Lanczos插值算法。在程序中，我们使用imread函数读取需要插值的图像，使用interp2函数进行插值计算。代码片段如下：

function outImg = lanczos_interp(img, scale)
    [m,n,~] = size(img);
    m_new = m*scale;
    n_new = n*scale;
    [x,y] = meshgrid(1:n_new, 1:m_new);
    x = x/scale;
    y = y/scale;
    outImg = zeros(m_new, n_new, 3);

    % 双线性插值
    for i=1:3
        outImg(:,:,i) = interp2(img(:,:,i), x, y, 'linear');

        % Lancaster插值
        for j=1:m_new
            for k=1:n_new
                if (ceil(x(j,k))-2)<1||(ceil(x(j,k))+3)>n||...
                    (ceil(y(j,k))-2)<1||(ceil(y(j,k))+3)>m       
                    continue;
                end
                Lanczosf = zeros(1,6);
                dx = x(j,k) - floor(x(j,k));
                dy = y(j,k) - floor(y(j,k));
                for x_offset=-2:3
                    distancex = dx - x_offset;
                    if distancex == 0
                        Lanczosf(x_offset+3) = 1;
                    else
                        Lanczosf(x_offset+3) = abs(sin(pi*distancex)*sin(pi*distancex/3)/(pi*distancex)^2);
                    end
                end

                l_r = 0;
                l_g = 0;
                l_b = 0;
                Lsum = 0;
                for x_offset=-2:3
                    for y_offset=-2:3
                        lanczosw = Lanczosf(x_offset+3)*Lanczosf(y_offset+3);
                        Lsum = Lsum+lanczosw;
                        l_r = l_r + img(ceil(y(j,k))+y_offset,ceil(x(j,k))+x_offset,1)*lanczosw;
                        l_g = l_g + img(ceil(y(j,k))+y_offset,ceil(x(j,k))+x_offset,2)*lanczosw;
                        l_b = l_b + img(ceil(y(j,k))+y_offset,ceil(x(j,k))+x_offset,3)*lanczosw;
                    end
                end
                outImg(j,k,1) = (l_r/Lsum);
                outImg(j,k,2) = (l_g/Lsum);
                outImg(j,k,3) = (l_b/Lsum);
            end
        end
    end
end