matlab双三次插值代码

以下是 MATLAB 的双三次插值代码：

function output = bicubic_interpolation(input, scale)
    [height, width] = size(input);
    new_height = round(height * scale);
    new_width = round(width * scale);
    output = zeros(new_height, new_width);
    for i = 1:new_height
        for j = 1:new_width
            x = i / scale;
            y = j / scale;
            if x < 3 || y < 3 || x > height - 2 || y > width - 2
                continue;
            end
            x1 = floor(x);
            x2 = x1 + 1;
            x3 = x1 + 2;
            x4 = x1 + 3;
            y1 = floor(y);
            y2 = y1 + 1;
            y3 = y1 + 2;
            y4 = y1 + 3;            dx = x - x1;
            dy = y - y1;
            d_matrix = [input(x1, y1), input(x1, y2), input(x1, y3), input(x1, y4);
                        input(x2, y1), input(x2, y2), input(x2, y3), input(x2, y4);
                        input(x3, y1), input(x3, y2), input(x3, y3), input(x3, y4);
                        input(x4, y1), input(x4, y2), input(x4, y3), input(x4, y4)];
            a_matrix = [-0.5, 1.5, -1.5, 0.5;
                        1, -2.5, 2, -0.5;
                        -0.5, 0, 0.5, 0;
                        0, 1, 0, 0];
            x_vector = [1, dx, dx^2, dx^3];
            y_vector = [1; dy; dy^2; dy^3];
            output(i, j) = x_vector * a_matrix * d_matrix * a_matrix' * y_vector;
        end
    end
    output = uint8(output);
end

其中，`input` 是输入的图像，`scale` 是缩放比例。函数返回的 `output` 是双三次插值后的图像。