jpeg解码matlab代码
时间: 2023-11-02 10:22:33 浏览: 44
以下是一个简单的JPEG解码Matlab代码,仅供参考:
```
function [im]=jpeg_decode(jpeg_filename)
%读取JPEG文件
fid=fopen(jpeg_filename,'r');
fseek(fid,0,'eof');
len=ftell(fid);
fseek(fid,0,'bof');
data=fread(fid,len,'uint8');
fclose(fid);
%找到Start of Frame (SOF)标记
idx=find(data==255);
for i=1:length(idx)-1
if data(idx(i)+1)==192
sof_idx=idx(i);
break;
end
end
%解码图像大小
height=data(sof_idx+5)*256+data(sof_idx+6);
width=data(sof_idx+7)*256+data(sof_idx+8);
%找到Start of Scan (SOS)标记
idx=find(data==255);
for i=1:length(idx)-1
if data(idx(i)+1)==218
sos_idx=idx(i);
break;
end
end
%解码扫描数据
data=data(sos_idx+2:end);
idx=find(data==255);
eob=idx(end);
data=data(1:eob-1);
data=bitget(data,8:-1:1);
data=reshape(data,8,[])';
data=bi2de(data);
data=data+1;
data=cumsum(data);
data=[0;data];
data=data(1:end-1)+1;
data=reshape(data,[],64);
data=data';
data=reshape(data,1,[]);
%解码量化表
idx=find(data==255);
for i=1:length(idx)-1
if data(idx(i)+1)==219
dqt_idx=idx(i);
break;
end
end
qtable=data(dqt_idx+5:dqt_idx+68);
%反量化
qtable=reshape(qtable,8,[])';
qtable=reshape(qtable,[],1);
Q=reshape(qtable,8,8);
Q=Q([1,3,5,7,2,4,6,8],[1,3,5,7,2,4,6,8]);
Q=reshape(Q',1,[]);
data=round(data.*Q);
%反DCT
block_size=8;
num_blocks=height/block_size*width/block_size;
im=zeros(height,width);
for i=1:num_blocks
x=mod(i-1,width/block_size)*block_size+1;
y=floor((i-1)/(width/block_size))*block_size+1;
block=data((i-1)*block_size^2+1:i*block_size^2);
block=reshape(block,block_size,block_size);
block=idct2(block);
im(y:y+block_size-1,x:x+block_size-1)=block;
end
%显示图像
imshow(im);
end
```