DCT简单图像压缩的OpenCV实现

利用DCT变换实现简单图像压缩：

1）对图像进行DCT变换

2）找出小于阈值T的DCT系数，并将其设置为0

3）进行DCT逆变换恢复图像

#include <opencv2/opencv.hpp>    
#include <math.h>  
#include <cv.h>  
#include <iostream>  
using namespace cv;  
  
double T = 40;  
  
int main()  
{  
    Mat src = imread("lena512.bmp");  
    imshow("Origin Image", src);  
  
    int h = src.rows;  
    int w = src.cols;  
    
    //从BGR空间转换到YUV空间（也可以不转换，直接在RGB空间）    
    Mat yuvimg(src.size(), CV_8UC3);  
    cvtColor(src, yuvimg, CV_BGR2YUV); //定义YUV空间图像为yuvimage  
    Mat dst(src.size(), CV_64FC3);     //定义输出图像为dst  
       
    //分割YUV通道  
    vector<Mat> channels;  
    split(yuvimg, channels);   
       
    //提取YUV颜色空间各通道    
    Mat Y = channels.at(0); imshow("Y image", Y);  
    Mat U = channels.at(1); imshow("U image", U);  
    Mat V = channels.at(2); imshow("V image", V);  
  
    //DCT系数的三个通道  
    Mat DCTY(src.size(), CV_64FC1);  
    Mat DCTU(src.size(), CV_64FC1);  
    Mat DCTV(src.size(), CV_64FC1);  
  
    //DCT变换  
    dct(Mat_<double>(Y), DCTY);  
    dct(Mat_<double>(U), DCTU);  
    dct(Mat_<double>(V), DCTV);  
  
    //Y通道压缩    
    for (int i = 0; i < h; i++)  
    {  
        double *p = DCTY.ptr<double>(i);  
        for (int j = 0; j < w; j++)  
        {  
            if (abs(p[j]) < T)  
                p[j] = 0;  
        }  
    }  
  
    //U通道压缩    
    for (int i = 0; i < h; i++)  
    {  
        double *p = DCTU.ptr<double>(i);  
        for (int j = 0; j < w; j++)  
        {  
            if (abs(p[j]) < T)  
                p[j] = 0;  
        }  
    }  
  
    //V通道压缩    
    for (int i = 0; i < h; i++)  
    {  
        double *p = DCTV.ptr<double>(i);  
        for (int j = 0; j < w; j++)  
        {  
            if (abs(p[j]) < T)  
                p[j] = 0;  
        }  
    }  
    Mat dstY(src.size(), CV_64FC1);  
    Mat dstU(src.size(), CV_64FC1);  
    Mat dstV(src.size(), CV_64FC1);  
  
    //DCT逆变换  
    idct(DCTY, dstY);     
    idct(DCTU, dstU);  
    idct(DCTV, dstV);  
  
    //merge方式1  
    //Mat planes[] = { Mat_<uchar>(dstB), Mat_<uchar>(dstG), Mat_<uchar>(dstR) };  
    //merge(planes, 3, yuvimg);   
    //cvtColor(yuvimg, dst, CV_YUV2BGR);  
    
    //merge方式2  
    channels.at(0) = Mat_<uchar>(dstY);  
    channels.at(1) = Mat_<uchar>(dstU);  
    channels.at(2) = Mat_<uchar>(dstV);  
    merge(channels, yuvimg);  
          
    //将压缩后图像从YUV空间重新转换到BGR空间  
    cvtColor(yuvimg, dst, CV_YUV2BGR);  
  
    imshow("Recoverd Y image", Mat_<uchar>(dstY));  
    imshow("Recoverd U image", Mat_<uchar>(dstU));  
    imshow("Recoverd V image", Mat_<uchar>(dstV));  
    imshow("DstImage", dst);  
  
    waitKey(0);  
  
    return 0;  
  
}