图片压缩 DCT变换 实时视频 2

上一篇的源码进行优化，将cosx运算提取出来，变成矩阵形式。

#include "stdafx.h"
#include <string.h>
#include <iostream>
#include <math.h>

using namespace std;
#define PI 3.1415926

int _tmain(int argc, _TCHAR* argv[])
{
    double        dInput[] = {0.0, 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0};
    int            iFactor[] = {1, 1, 1, 1, 0, 0, 0, 0, 0, 0};
    double        dOut[10] = {0};
    double        dOut1[10]= {0};
    
    const int N = sizeof(dInput)/sizeof(double);
    double*        pdFactor = new double[N*N];

    for (int row=0; row<N; row++)
    {
        for (int col=0; col<N; col++)
        {
            if (row==0)
                pdFactor[row*N+col] = cos((2*col + 1)*PI*row/(2*N)) / sqrt((double)N);
            else
                pdFactor[row*N+col] = cos((2*col + 1)*PI*row/(2*N)) * sqrt(2.0) / sqrt((double)N);
        }
    }

    for (int i=0; i<N; i++)
    {
        for (int j=0; j<N; j++)
        {
            dOut[i]+= dInput[j] * pdFactor[i*N+j];
        }
    }
    printf("\n变换前：\n");
    for (int i=0; i<N; i++)
    {
        printf("%f\t", dInput[i]);
    }

    printf("\n变换后：\n");
    for (int i=0; i<N; i++)
    {
        printf("%f\t", dOut[i]);
    }

    //printf("\n去除高频：\n");
    //for (int i=0; i<N; i++)
    //{
    //    dOut[i] *= iFactor[i];
    //    printf("%f\t", dOut[i]);
    //}

    printf("\n逆变换：\n");
    for (int i=0; i<N; i++)
    {
        for (int j=0; j<N; j++)
        {
            dOut1[i]+= dOut[j] * pdFactor[j*N+i];
        }
    }

    for (int i=0; i<N; i++)
    {
        printf("%f\t", dOut1[i]);
    }

    getchar();
    delete[] pdFactor;
}

 由此源码发现。

 参数因子pdFactor,由编码的逐行积相加，变为解码的逐列的积相加。