如何在分辨率不变的情况下进行图像放大？要求用到插值方法

我也想知道~~~

内插法：
ratio=input('please input ratio:');
a=imread('1.jpg');
imshow(a);
[row,col,n]=size(a);
r1=round(row*ratio);
c1=round(col*ratio);
b=zeros(r1,c1,n);

    for i=1:r1
        for j=1:c1
            i1=round(i/ratio);
            j1=round(j/ratio);
            if i1<1
                i1=1;
            end
            if j1<1
                j1=1;
            end
       b(i,j,1)=a(i1,j1,1);
       b(i,j,2)=a(i1,j1,2);
       b(i,j,3)=a(i1,j1,3);
     end
 end
 
 b=uint8(b);
 figure;
 imshow(b);