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compression2.m
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function compression2
path = "D:\Project\dataset\Helen\";
Qua_Factor=90;%量化因子,最小为0.01,最大为255,建议在0.5和3之间,越小质量越好文件越大
k = 12;
p = 4;
thr = 4;
for Qua_Factor = 60:10:80
mkdir('D:\Project\ID3\experiments\Helen', strcat('Q=',num2str(Qua_Factor)));
for xx = 1 : 100
xx
filename = strcat(path,num2str(xx),".png");
img=imread(filename);
img_ycbcr = rgb2ycbcr(img); % rgb->yuv转换
[row,col,~]=size(img_ycbcr); % 取出行列数，~表示3个通道算1列
%对图像进行扩展
row_expand=ceil(row/16)*16; %行数上取整再乘16，及扩展成16的倍数
if mod(row,16)~=0 %行数不是16的倍数，用最后一行进行扩展
for i=row:row_expand
img_ycbcr(i,:,:)=img_ycbcr(row,:,:);
end
end
col_expand=ceil(col/16)*16; %列数上取整
if mod(col,16)~=0 %列数不是16的倍数，用最后一列进行扩展
for j=col:col_expand
img_ycbcr(:,j,:)=img_ycbcr(:,col,:);
end
end
%对Y,Cb,Cr分量进行4:2:2采样
Y=img_ycbcr(:,:,1); %Y分量
Cb=zeros(row_expand/2,col_expand/2); %Cb分量
Cr=zeros(row_expand/2,col_expand/2); %Cr分量
for i=1:row_expand/2
for j=1:2:col_expand/2-1 %奇数列
Cb(i,j)=double(img_ycbcr(i*2-1,j*2-1,2));
Cr(i,j)=double(img_ycbcr(i*2-1,j*2+1,3));
end
end
for i=1:row_expand/2
for j=2:2:col_expand/2 %偶数列
Cb(i,j)=double(img_ycbcr(i*2-1,j*2-2,2));
Cr(i,j)=double(img_ycbcr(i*2-1,j*2,3));
end
end
%分别对三种颜色分量进行编码
Y_Table=[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];%亮度量化表
CbCr_Table=[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];%色差量化表
%对三个通道分别DCT和量化
Y_dct_q=Dct_Quantize(Y,Qua_Factor,Y_Table);
Cb_dct_q=Dct_Quantize(Cb,Qua_Factor,CbCr_Table);
Cr_dct_q=Dct_Quantize(Cr,Qua_Factor,CbCr_Table);
Y_in_q_dct=Inverse_Quantize_Dct(Y_dct_q,Qua_Factor,Y_Table);
Cb_in_q_dct=Inverse_Quantize_Dct(Cb_dct_q,Qua_Factor,CbCr_Table);
Cr_in_q_dct=Inverse_Quantize_Dct(Cr_dct_q,Qua_Factor,CbCr_Table);
%恢复出YCBCR图像
YCbCr_in = uint8(zeros([row_expand col_expand 3]));
YCbCr_in(:,:,1)=Y_in_q_dct;
for i=1:row_expand/2
for j=1:col_expand/2
YCbCr_in(2*i-1,2*j-1,2)=Cb_in_q_dct(i,j);
YCbCr_in(2*i-1,2*j,2)=Cb_in_q_dct(i,j);
YCbCr_in(2*i,2*j-1,2)=Cb_in_q_dct(i,j);
YCbCr_in(2*i,2*j,2)=Cb_in_q_dct(i,j);
YCbCr_in(2*i-1,2*j-1,3)=Cr_in_q_dct(i,j);
YCbCr_in(2*i-1,2*j,3)=Cr_in_q_dct(i,j);
YCbCr_in(2*i,2*j-1,3)=Cr_in_q_dct(i,j);
YCbCr_in(2*i,2*j,3)=Cr_in_q_dct(i,j);
end
end
I_in=ycbcr2rgb(YCbCr_in);
I_in(row+1:row_expand,:,:)=[];%去掉扩展的行
I_in(:,col+1:col_expand,:)=[];%去掉扩展的列
I_th = Thumbnail(I_in,8);
imwrite(I_in,strcat('D:\Project\ID3\experiments\Helen\', strcat('Q=',num2str(Qua_Factor),"\",num2str(xx),".jpg")));
imwrite(I_th,strcat('D:\Project\ID3\experiments\Helen\', strcat('Q=',num2str(Qua_Factor),"\th_",num2str(xx),".jpg")));
end
end
end