待更新

梦里梦外; 2022-07-19 00:21 307阅读 0赞

mark

图像压缩

# [OpenCV探索之路（十八）：使用imwrite调整保存的图片质量][OpenCV_imwrite] #

[DCT简单图像压缩的OpenCV实现][DCT_OpenCV]

**OpenCV实现基于8\*8块DCT变换的图像压缩**

void DctCompresss(const Mat& src, Mat& match , double T)
    {
    
    	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> YUV;
    	split(yuvimg, YUV);
    
    	//先转换下格式  
    	Mat float_Y, float_U, float_V;
    	YUV[0].convertTo(float_Y, CV_64FC1);
    	YUV[1].convertTo(float_U, CV_64FC1);
    	YUV[2].convertTo(float_V, CV_64FC1);
    
    	//基于8*8块的DCT变换及其反变换  
    	Rect windows;        //利用这个8*8的矩形来进行8*8块的DCT变换  
    	//DCT变换  
    	Mat DCTU, DCTV, DCTY;
    	float_Y.copyTo(DCTY);
    	float_U.copyTo(DCTU);
    	float_V.copyTo(DCTV);
    
    	for (int i = 0; i < src.cols / 8; i++)
    	{
    		for (int j = 0; j < src.rows / 8; j++)
    		{
    			windows.x = 8 * i;
    			windows.y = 8 * j;
    			windows.height = 8;
    			windows.width = 8;
    			dct(float_Y(windows), DCTY(windows));
    			dct(float_U(windows), DCTU(windows));
    			dct(float_V(windows), DCTV(windows));
    		}
    	}
    
    	//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;
    		}
    	}
    
    	//反DCT变换  
    	for (int i = 0; i < src.cols / 8; i++)
    	{
    		for (int j = 0; j < src.rows / 8; j++)
    		{
    			windows.x = 8 * i;
    			windows.y = 8 * j;
    			windows.height = 8;
    			windows.width = 8;
    			dct(DCTY(windows), float_Y(windows), DCT_INVERSE);
    			dct(DCTU(windows), float_U(windows), DCT_INVERSE);
    			dct(DCTV(windows), float_V(windows), DCT_INVERSE);
    		}
    	}
    
    	vector<Mat> YUV_dst(3);
    	//格式转换  
    	float_Y.convertTo(YUV_dst[0], CV_8UC1);
    	float_U.convertTo(YUV_dst[1], CV_8UC1);
    	float_V.convertTo(YUV_dst[2], CV_8UC1);
    
    	//将三个通道进行合并  
     
    	merge(YUV_dst, yuvimg);
     
    	//将压缩后图像从YUV空间重新转换到BGR空间    
    	cvtColor(yuvimg, dst, CV_YUV2BGR);
    
    	match = dst;
    }

[OpenCV_imwrite]: http://www.cnblogs.com/skyfsm/p/7136709.html
[DCT_OpenCV]: http://blog.csdn.net/xfijun/article/details/51040128