1.基于DCT的圖像壓縮方法是將一幅圖像分割成矩形像素塊，再分別對每一獨立的像素塊DCT變換、量化、編碼和傳輸。

2.打開VS2010，新建Visual C++下Win32控制臺應用程序demo，主程序如下：

// demo.cpp : 定義控制臺應用程序的入口點。
//

#include "stdafx.h"
#include "highgui.h"
#include <math.h>
#include <cv.h>
#include "cxcore.h"
#define cvCvtPlaneToPix cvMerge
double PSNR_B = 0;?
double PSNR_G = 0;?
double PSNR_R = 0;?
double PSNR;?

int _tmain(int argc, _TCHAR* argv[])
{
?const char* imagename = "D:/demo/demo.jpg";
?IplImage *src;?
??? CvScalar SrcPixel;?
??? CvScalar DstPixel;?
??? double sumB = 0;?
??? double sumG = 0;?
??? double sumR = 0;?
??? double mseB;?
??? double mseG;?
??? double mseR;?
?
??? src= cvLoadImage( imagename,1 ) ;???
??? if( !src )?
??? {?
??????? printf("can't open the image...\n");?
??????? return -1;?
??? }?
??? // YUV顏色空間??
??? IplImage* YUVImage = cvCreateImage(cvSize(src->width,src->height), src->depth, 3);?
??? IplImage* dst = cvCreateImage(cvSize(src->width,src->height), src->depth, 3);?
??? // YUV顏色空間各通道??
??? IplImage* Y = cvCreateImage(cvSize(src->width,src->height), IPL_DEPTH_8U, 1);?
??? IplImage* U = cvCreateImage(cvSize(src->width,src->height), IPL_DEPTH_8U, 1);?
??? IplImage* V = cvCreateImage(cvSize(src->width,src->height), IPL_DEPTH_8U, 1);?
?????
?????
??? //cvNamedWindow( "Origin Image", CV_WINDOW_AUTOSIZE );??
??? cvCvtColor(src, YUVImage, CV_BGR2YUV); //BGR→YUV??
??? cvSplit( YUVImage, Y, U, V, NULL);//分割通道??
?????
??? CvMat* MatY = cvCreateMat(Y->height,Y->width,CV_64FC1);?
??? CvMat* MatU = cvCreateMat(V->height,U->width,CV_64FC1);?
??? CvMat* MatV = cvCreateMat(V->height,V->width,CV_64FC1);?
?
??? CvMat* DCTY = cvCreateMat(Y->height, Y->width,CV_64FC1);?
??? CvMat* DCTU = cvCreateMat(U->height, U->width,CV_64FC1);?
??? CvMat* DCTV = cvCreateMat(V->height, V->width,CV_64FC1);?
?????
??? cvScale( Y, MatY );?
??? cvScale( U, MatU );?
??? cvScale( V, MatV );?
?
??? cvDCT(MatY, DCTY, CV_DXT_FORWARD); //余弦變換??
??? cvDCT(MatU, DCTU, CV_DXT_FORWARD); //余弦變換??
??? cvDCT(MatV, DCTV, CV_DXT_FORWARD); //余弦變換??
?????
??? //Y 通道壓縮??
??? for(int i = 0; i < Y->height; i++)???
??? {?
??????? for(int j = 0; j < Y->width; j++)?
??????? {?
??????????? double? element = CV_MAT_ELEM( *DCTY, double, i, j );?
??????????? if ( abs(element) < 10 )?
??????????????? CV_MAT_ELEM( *DCTY, double, i, j ) = 0;?
??????? }?
??? }?
?
??? // U 通道壓縮??
??? for(int i = 0; i < U->height; i++)???
??? {?
??????? for(int j = 0; j < U->width; j++)?
??????? {?
??????????? double? element = CV_MAT_ELEM( *DCTU, double, i, j );?
??????????? if (???? abs(element) < 20 )?
??????????????? CV_MAT_ELEM( *DCTU, double, i, j ) = 0;?
??????? }?
??? }?
?
??? // V 通道壓縮??
??? for(int i = 0; i < V->height; i++)???
??? {?
??????? for(int j = 0; j < V->width; j++)?
??????? {?
??????????? double? element = CV_MAT_ELEM( *DCTV, double, i, j );?
??????????? if (???? abs(element) < 20 )?
??????????????? CV_MAT_ELEM( *DCTV, double, i, j ) = 0;?
??????? }?
??? }?
??? cvDCT(DCTY, MatY, CV_DXT_INVERSE); //余弦反變換??
??? cvDCT(DCTU, MatU, CV_DXT_INVERSE);??
??? cvDCT(DCTV, MatV, CV_DXT_INVERSE);??
?
??? cvScale( MatY, Y );?
??? cvScale( MatU, U );?
??? cvScale( MatV, V );?
?????
??? cvMerge( Y, U, V, NULL, YUVImage );?
??? cvCvtColor( YUVImage, dst, CV_YUV2BGR); //YUV→BGR??
?
??? //? 計算前后兩幅圖像的PSNR值??
??? for(int i = 0; i < src->height; i++)?
??? {?
??????? for(int j = 0; j < src->width; j++)?
??????? {?
??????????? SrcPixel = cvGet2D( src, i, j );?
??????????? DstPixel = cvGet2D( dst, i, j );?
??????????? sumB += ( SrcPixel.val[0] - DstPixel.val[0] ) * ( SrcPixel.val[0] - DstPixel.val[0] );?
??????????? sumG += ( SrcPixel.val[1] - DstPixel.val[1] ) * ( SrcPixel.val[1] - DstPixel.val[1] );?
??????????? sumR += ( SrcPixel.val[2] - DstPixel.val[2] ) * ( SrcPixel.val[2] - DstPixel.val[2] );?
?????????????
??????? }?
??? }?
??? mseB = sumB / ((src->width) * (src->height)); //計算均方差??
??? mseG = sumG / ((src->width) * (src->height));??
??? mseR = sumR / ((src->width) * (src->height));??
?
??? PSNR_B = 10.0 * ( log10( 255.0 * 255.0 / mseB ) );?
??? PSNR_G = 10.0 * ( log10( 255.0 * 255.0 / mseG ) );?
??? PSNR_R = 10.0 * ( log10( 255.0 * 255.0 / mseR ) );?
??? PSNR=(PSNR_B + PSNR_G + PSNR_R) / 3;?
?????
??? cvShowImage( "YImage", Y );?
??? cvShowImage( "UImage", U );?
??? cvShowImage( "VImage", V );?
??? cvShowImage( "DstImage", dst );?
??? cvSaveImage( "D:/demo/dstdemo.jpg", dst);?
?
??? while( 1 )?
??? {?
??????? if( cvWaitKey(0) == 27 ) break;?
??? }?
?
??? cvDestroyWindow("YImage");?
??? cvDestroyWindow("UImage");?
??? cvDestroyWindow("VImage");?
??? cvDestroyWindow("DstImage");?
?
?????
??? cvReleaseImage(&Y);?
??? cvReleaseImage(&U);?
??? cvReleaseImage(&V);?
??? cvReleaseImage(&src);?
??? cvReleaseImage(&dst);?
??? cvReleaseImage(&YUVImage);?
?
??? return 0;?

}

?

3.參考用，jpg圖片越壓縮越大，代碼有待優化來達到壓縮效果！

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