jpg_dct.m

实现基本JPEG的压缩和编码 ％ 1． 首先通过DCT变换去除数据冗余； ％ 2． 使用量化表对DCT系数进行量化； ％ 3． 对量化后的系数进行Huffman编码。

%%%%%%%%%% 实现基本JPEG的压缩和编码 %%%%%%%%%%%%
% 1． 首先通过DCT变换去除数据冗余；
% 2． 使用量化表对DCT系数进行量化；
% 3． 对量化后的系数进行Huffman编码。
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

clear;
clc;
%%%%%%%%%%%%%%%%%%%%%%
%%1．主程序
%%%%%%%%%%%%%%%%%%%%%%
I=imread('lenna.bmp');
yiq=rgb2ntsc(I); % transform RGB to NTSC



my=[16 11 10 16 24 40 51 61;
12 12 14 19 26 58 60 55;
14 13 16 24 40 57 69 56;
14 17 22 29 51 87 80 62;
18 22 37 56 68 109 103 77;
24 35 55 64 81 104 113 92;
49 64 78 87 103 121 120 101;
72 92 95 98 112 100 103 99];



miq=[17 18 24 47 99 99 99 99;
18 21 26 66 99 99 99 99;
24 26 56 99 99 99 99 99;
47 66 99 99 99 99 99 99;
99 99 99 99 99 99 99 99;
99 99 99 99 99 99 99 99;
99 99 99 99 99 99 99 99;
99 99 99 99 99 99 99 99];



I1=yiq(:, :, 1);
I2=yiq(:, :, 2);
[m n]=size(I1);



t1=8;
ti1=1;
while (t1<(m+8))
t1=t1+8;
ti1=ti1+1;
end



t2=8;
ti2=1;
while (t2<(n+8))
t2=t2+8;
ti2=ti2+1;
end



times=0;
for k=0:ti1-2
for j=0:ti2-2
dct8x8(I1(k*8+1:k*8+8,j*8+1:j*8+8),my,times*64+1);
dct8x8(I2(k*8+1:k*8+8,j*8+1:j*8+8),miq,times*64+1);
times=times+1;
end
block(I2(k*8+1:k*8+8,j*8+1:t2),[8 8], 'dctmtx(8)');
end



for j=0:ti2-2
dct8x8(I1(k*8+1:t1,j*8+1:j*8+8),times*64+1);
times=times+1;
end



dct8x8(I1(k*8+1:t1,j*8+1:t2),times*64+1);



%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%2．function dct8x8(I,m,s) %定义DCT量化子程序
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
function dct8x8(I,m,s)
T=inline('dctmtx(8)');
y=blkproc(I,[8 8],T);
y=round(y./m);
p=1;te=1;
while (p<=64)
for q=1:te
y1(s+p)=y(te-q+1,q);p=p+1;
end
for q=te:-1:1
y1(s+p)=y(te-q+1,q);p=p+1;
end
end



f=haffman(y1);
c(s:s+64,1)=f(:,1);
c(s:s+64,2)=f(:,2);
c(s:s+64,3)=f(:,3)



%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%3．function c=haffman(I) %定义Huffman编码子程序
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
[m,n]=size(I);
p1=1;
s=m*n;
for k=1:m
for h=1:n
f=0;
for b=1:p1-1
if (c(b,1)==I(k,h)) 
f=1;
break;
end
end
if (f==0) 
c(p1,1)=I(k,h);
p1=p1+1;
end
end
end



for g=1:p1-1
p(g)=0;c(g,2)=0;
for k=1:m
for h=1:n
if (c(g,1)==I(k,h)) 
p(g)=p(g)+1;
end
end
end
p(g)=p(g)/s;
end



pn=0;po=1;
while (1)
if(pn>=1.0) 
break;
else
[pm p2]=min(p(1:p1-1));
p(p2)=1.1;
[pm2,p3]=min(p(1:p1-1));
p(p3)=1.1;
pn=pm+pm2;
p(p1)=pn;
tree(po,1)=p2;
tree(po,2)=p3;
po=po+1;
p1=p1+1;
end
end



for k=1:po-1
tt=k;
m1=1;
if (or(tree(k,1)<9,tree(k,2)<9))
if (tree(k,1)<9)
c(tree(k,1),2)=c(tree(k,1),2)+m1;
m2=1;
while(tt)
m1=m1*2;
for h=tt:po-1
if (tree(h,1)==tt+g)
c(tree(k,1),2)=c(tree(k,1),2)+m1;
m2=m2+1;
tt=h;
break;
elseif (tree(h,2)==tt+g)
m2=m2+1;
tt=h;
break;
end
end
end
c(tree(k,1),3)=m2;
end
tt=k;
m1=1;
if (tree(k,2)<9)
m2=1;
while (tt)
m1=m1*2;
for h=tt:po-1
if (tree(h,1)==tt+g)
c(tree(k,2),2)=c(tree(k,2),2)+m1;
m2=m2+1;
tt=h;
break;
elseif (tree(l,2)==tt+g)
m2=m2+1,
tt=h;
break;
end
end
dct8x8(I1(k*8+1:k*8+8,j*8+1:j*8+8),my,times*64+1);
dct8x8(I2(k*8+1:k*8+8,j*8+1:j*8+8),miq,times*64+1);
times=times+1;
end
c(tree(k,2),3)=m2;
end
end
end