www.pudn.com > spiht-0.3.rar > func_SPIHT_Dec.m
function m = func_SPIHT_Dec(in_stream)
% Matlab implementation of SPIHT (without Arithmatic coding stage)
%
% Decoder
%
% input: in_stream: input compression file stream
%
% output: m : reconstructed image in wavelet domain
%
% Jing Tian
% Contact me : scuteejtian@hotmail.com
% This program is part of my undergraduate project in GuangZhou, P. R. China.
% April - July 1999
%--------------here updata by swf000117@sina.com------------
fid=fopen(in_stream,'rb');
in(1,1)=fread(fid,1,'short');
in(1,2)=fread(fid,1,'uchar');
in(1,3)=fread(fid,1,'uchar');
in(1,4)=fread(fid,1,'float');
%max_bytes=in(1,1)^2*in(1,4)/8-2-1-1-4-1;
a=fread(fid,'uchar');
fclose(fid);
max_bytes=length(a);
for i=1:max_bytes
for j=1:8
in(1,8*(i-1)+5+j-1)=bitget(a(i),j);
end
end
%----------- Initialization -----------------
% image size, number of bit plane, wavelet decomposition level should be
% written as bit stream header.
m = zeros(in(1,1));
n_max = in(1,2);
level = in(1,3);
rate= in(1,4);
ctr = 5;
max_bits=8*max_bytes+4-16;%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%----------- Initialize LIP, LSP, LIS ----------------
temp = [];
bandsize = 2.^(log2(in(1,1)) - level + 1);
temp1 = 1 : bandsize;
for i = 1 : bandsize
temp = [temp; temp1];
end
LIP(:, 1) = temp(:);
temp = temp';
LIP(:, 2) = temp(:);
LIS(:, 1) = LIP(:, 1);
LIS(:, 2) = LIP(:, 2);
LIS(:, 3) = zeros(length(LIP(:, 1)), 1);
pstart = 1;
pend = bandsize / 2;
for i = 1 : bandsize / 2
LIS(pstart : pend, :) = [];
pdel = pend - pstart + 1;
pstart = pstart + bandsize - pdel;
pend = pend + bandsize - pdel;
end
LSP = [];
%----------- coding ----------------
n = n_max;
while (n>=0) %(ctr <= size(in,2))
%Sorting Pass
LIPtemp = LIP; temp = 0;
for i = 1:size(LIPtemp,1)
temp = temp+1;
if ctr > max_bits
return
end
if in(1,ctr) == 1
ctr = ctr + 1;
if in(1,ctr) > 0
m(LIPtemp(i,1),LIPtemp(i,2)) = 2^n + 2^(n-1);
else
m(LIPtemp(i,1),LIPtemp(i,2)) = -2^n - 2^(n-1);
end
LSP = [LSP; LIPtemp(i,:)];
LIP(temp,:) = []; temp = temp - 1;
end
ctr = ctr + 1;
end
LIStemp = LIS; temp = 0; i = 1;
while ( i <= size(LIStemp,1))
temp = temp + 1;
if ctr > max_bits
return
end
if LIStemp(i,3) == 0
if in(1,ctr) == 1
ctr = ctr + 1;
x = LIStemp(i,1); y = LIStemp(i,2);
if ctr > max_bits
return
end
if in(1,ctr) == 1
LSP = [LSP; 2*x-1 2*y-1];
ctr = ctr + 1;
if in(1,ctr) == 1
m(2*x-1,2*y-1) = 2^n + 2^(n-1);
else
m(2*x-1,2*y-1) = -2^n - 2^(n-1);
end
ctr = ctr + 1;
else
LIP = [LIP; 2*x-1 2*y-1];
ctr = ctr + 1;
end
if ctr > max_bits
return
end
if in(1,ctr) == 1
ctr = ctr + 1;
LSP = [LSP; 2*x-1 2*y];
if in(1,ctr) == 1;
m(2*x-1,2*y) = 2^n + 2^(n-1);
else
m(2*x-1,2*y) = -2^n - 2^(n-1);
end
ctr = ctr + 1;
else
LIP = [LIP; 2*x-1 2*y];
ctr = ctr + 1;
end
if ctr > max_bits
return
end
if in(1,ctr) == 1
ctr = ctr + 1;
LSP = [LSP; 2*x 2*y-1];
if in(1,ctr) == 1
m(2*x,2*y-1) = 2^n + 2^(n-1);
else
m(2*x,2*y-1) = -2^n - 2^(n-1);
end
ctr = ctr + 1;
else
LIP = [LIP; 2*x 2*y-1];
ctr = ctr + 1;
end
if ctr > max_bits
return
end
if in(1,ctr) == 1
ctr = ctr + 1;
LSP = [LSP; 2*x 2*y];
if in(1,ctr) == 1
m(2*x,2*y) = 2^n + 2^(n-1);
else
m(2*x,2*y) = -2^n - 2^(n-1);
end
ctr = ctr + 1;
else
LIP = [LIP; 2*x 2*y];
ctr = ctr + 1;
end
if ((2*(2*x)-1) < size(m) & (2*(2*y)-1) < size(m))
LIS = [LIS; LIStemp(i,1) LIStemp(i,2) 1];
LIStemp = [LIStemp; LIStemp(i,1) LIStemp(i,2) 1];
end
LIS(temp,:) = []; temp = temp-1;
else
ctr = ctr + 1;
end
else
if in(1,ctr) == 1
x = LIStemp(i,1); y = LIStemp(i,2);
LIS = [LIS; 2*x-1 2*y-1 0; 2*x-1 2*y 0; 2*x 2*y-1 0; 2*x 2*y 0];
LIStemp = [LIStemp; 2*x-1 2*y-1 0; 2*x-1 2*y 0; 2*x 2*y-1 0; 2*x 2*y 0];
LIS(temp,:) = []; temp = temp - 1;
end
ctr = ctr + 1;
end
i = i+1;
end
% Refinement Pass
temp = 1;
value = m(LSP(temp,1), LSP(temp,2));
while (abs(value) >= 2^(n+1) & (temp <= size(LSP,1)))
if ctr > max_bits
return
end
value = value + ((-1)^(in(1,ctr) + 1)) * (2^(n-1))*sign(m(LSP(temp,1),LSP(temp,2)));
m(LSP(temp,1),LSP(temp,2)) = value;
ctr = ctr + 1;
temp = temp + 1;
if temp <= size(LSP,1)
value = m(LSP(temp,1),LSP(temp,2));
end
end
n = n-1;
end