function outImg = downSample( origImg, scale ,type)
%UNTITLED Summary of this function goes here
% Detailed explanation goes here
origImg = double(origImg);
[M,N,P] = size(origImg);
m = ceil(M/scale);
n = ceil(N/scale);
outImg = uint8(zeros(m,n,P));
col = (M/m) .*(1:m) - (M/(2*m));
row = (N/n) .*(1:n) - (N/(2*n));
switch type
%最邻近采样法
case 'nearest'
outImg(:,:,:) = uint8(origImg(ceil(col),ceil(row),:));
%二次差值法
case 'linear'
u = col;
v = row;
col = fix(col);
row = fix(row);
col(col==0) = 1;
row(row==0) = 1;
u = u - col;
v = v - row;
for i = 1:P
outImg(:,:,i) = uint8(((1-u)'*(1-v)).*origImg(col,row,i)+...
((1-u)'*v).*origImg(col,row+1,i)+...
(u'*(1-v)).*origImg(col+1,row,i)+...
(u'*v).*origImg(col+1,row+1,i));
end
%双三次卷积法
case 'cubic'
u = col - fix(col);
v = row - fix(row);
origImg = cat(1,origImg(1,:,:),origImg,origImg(end,:,:),origImg(end,:,:));
origImg = cat(2,origImg(:,1,:),origImg,origImg(:,end,:),origImg(:,end,:));
col = ceil(col) + 1;
row = ceil(row) + 1;
for a = 1:P
for i = 1:m
for j = 1:n
A = [S(1+v(j)),S(v(j)),S(1-v(j)),S(2-v(j))];
C = [S(1+u(i)),S(u(i)),S(1-u(i)),S(2-u(i))];
B = origImg((col(i)-1):(col(i)+2),(row(j)-1):(row(j)+2),a);
outImg(i,j,a) = A * B * C';
end
end
end
outImg = uint8(outImg);
end
end
