JPEG.rar_jpeg

%function JPEGEncodeDecode %UNTITLED7 Summary of this function goes here % Detailed explanation goes here clc; clear all; img=imread('slena.bmp'); subplot(121);imshow(img);title('原图'); %显示原图 img_ycbcr = rgb2ycbcr(img); % rgb->yuv [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4:2:0采样 Y=img_ycbcr(:,:,1); %Y分量 Cb=zeros(row_expand/2,col_expand/2); %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 Qua_Factor=0.5;%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 %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); %对三个通道分别反量化和反DCT 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(:,:,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 imwrite(I_in,'compressed_lena.bmp'); subplot(122);imshow(I_in);title('重构后的图片');