图像像素灰度内插(Matlab实现)

常用的像素灰度内插法：最近邻元法、双线性内插法、三次内插法

%%像素灰度内插
factor = 0.75;%缩放比
u = 0.6;v = 0.7;
itp1 = uint8(zeros(ceil(h/factor),ceil(w/factor)));
itp2 = uint8(zeros(ceil(h/u),ceil(w/v)));
itp3 = uint8(zeros(ceil(h/u),ceil(w/v)));

下述的J3为待插值灰度图像，itp为插值图像

1.最近邻元法

         在待求像素的四邻像素中，将距离这点最近的邻像素灰度赋给待求像素。

%最近邻元法
 for i = 1:h/factor
    for j = 1:w/factor
        itp1(i,j) = J3(floor(i*factor+0.5),floor(j*factor+0.5));
    end
 end

2.双线性内插法

%双线性内插法
for i = 2:h/u-1
    for j = 2:w/v-1
        itp2(i,j) = (1-(i*u-floor(i*u)))*(1-(j*v-floor(j*v)))*J3(floor(i*u),floor(j*v))...
                   +(1-(i*u-floor(i*u)))*(j*v-floor(j*v))*J3(floor(i*u),floor(j*v)+1)...
                   +(i*u-floor(i*u))*(1-(j*v-floor(j*v)))*J3(floor(i*u)+1,floor(j*v))...
                   +(i*u-floor(i*u))*(j*v-floor(j*v))*J3(floor(i*u)+1,floor(j*v)+1);         

    end
end

3.三次内插法

function [f] = S(x)
if (0<=abs(x))&&(abs(x)<1)
    f = 1-2*(abs(x))^2+(abs(x))^3;
elseif (1<=abs(x))&&(abs(x)<2)
    f = 4-8*abs(x)+5*(abs(x))^2-(abs(x))^3;
else
    f = 0;
end
end


%三次内插法
f = double(J3);
u = 0.6;v = 0.7;
for i = ceil(2/u):h/u-2
    for j = ceil(2/v):w/v-2
       A = [S(1+(j*v-floor(j*v))) S((j*v-floor(j*v))) S(1-(j*v-floor(j*v))) S(2-(j*v-floor(j*v)))];
       C = [S(1+(i*u-floor(i*u)));S((i*u-floor(i*u)));S(1-(i*u-floor(i*u)));S(2-(i*u-floor(i*u)))];
       i1 = floor(i*u); j1 = floor(j*v);
       B = [f(i1-1,j1-1) f(i1-1,j1) f(i1-1,j1+1) f(i1-1,j1+2);
            f(i1,j1-1) f(i1,j1) f(i1,j1+1) f(i1,j1+2);
            f(i1+1,j1-1) f(i1+1,j1) f(i1+1,j1+1) f(i1+1,j1+2);
            f(i1+2,j1-1) f(i1+2,j1) f(i1+2,j1+1) f(i1+2,j1+2);];
        itp3(i,j) = A*B*C;
    end
end

上述的内插法处理的结果出现了黑边，可以通过将黑边区域赋予原始图像的对应区域的像素灰度值。

可通过以下循环实现。

%去黑边
    [m,n] = size(J3);%原始图像的行列数

    for i = 1:floor(1/u) 
        for j = 1:floor(n/v)
          itp(i,j) = J3(ceil(i*u),ceil(j*v));
          itp(floor(m/u),j) = J3(m,ceil(j*v));
        end
    end
    for j = 1:floor(1/v)
        for i = 1:floor(m/u)
           itp(i,j) = J3(ceil(i*u),ceil(j*v));
           itp(i,floor(n/v)) = J3(ceil(i*u),n);
        end
    end