yuv420格式(微信图片存储路径)

大家好，又见面了，我是你们的朋友全栈君。

       网上大多数关于YUV420的资料都是关于YUV420P的，很少有YUV420SP的，因为YUV420SP的UV是交错存放的，处理起来相对麻烦点，但是YUV420SP也是一种常见格式，因此，在这里，我将关于YUV420SP格式数据的处理总结下，方便有需要的同志。

一、YUV420格式数据介绍

               

二、从YUV内存中取数据组方法

       注意YUV是每四个Y对应一个UV,并且YUV420P和YUV420SP的UV的存放格式不同，取法也不同，总的来说，YUV420P的取法简单，YUV420SP的取法相对复杂点。

1、YUV420SP

for(int j=0;j<DataHeight;j++)   
{  
    for(int i=0;i<DataWidth;i++)  
    {  
        y=ybase[i + j * DataWidth];// 每四个y对应一个uv  
        u=ubase[j/2 * DataWidth+(i/2)*2];  
        v=ubase[j/2 * DataWidth+(i/2)*2+1];  //一定要注意是u+1      
    }  
} 

2、YUV420P

for(int j=0;j<DataHeight;j++)   
{  
    for(int i=0;i<DataWidth;i++)  
    {  
        //yyyyyy ... uuuu ...vvv
        y=ybase[i + j * DataWidth];
        u=ubase[j/2 * DataWidth/2+(i/2)];  
        v=vbase[j/2 * DataWidth/2+(i/2)];  
    }  
} 

上面代码里，ybase就是YUV中Y的起始地址，ubase就是u的起始地址，vbase就是v的起始地址。而YUV420SP格式中，V就是U的地址加一；YUV420P中U和V都是连续的。按照上面方法，我们就可以得到每一组YUV数据，然后自己可以将每一组数据保存下来，再进行处理。

三、YUV420转换为RGB数据

1、转换公式

R=Y+1.4075*(V-128)
G=Y-0.3455*(U-128) – 0.7169*(V-128)
B=Y+1.779*(U-128)

2.转换方法

YUV420SP

for(int j=0;j<DataHeight;j++)   
{  
    for(int i=0;i<DataWidth;i++)  
    {  
        unsigned char r,g,b;  
        y=ybase[i + j * DataWidth];
        u=ubase[j/2 * DataWidth+(i/2)*2];  
        v=ubase[j/2 * DataWidth+(i/2)*2+1];      

        b=(unsigned char)(y+1.779*(u- 128));  
        g=(unsigned char)(y-0.7169*(v - 128)-0.3455*(u - 128));    
        r=(unsigned char)(y+ 1.4075*(v - 128));*/  
    }  
}  

YUV420P

for(int j=0;j<DataHeight;j++)   
{  
    for(int i=0;i<DataWidth;i++)  
    {  
        unsigned char r,g,b;  
      
        y=ybase[i + j * DataWidth];
        u=ubase[j/2 * DataWidth/2+(i/2)];  
        v=vbase[j/2 * DataWidth/2+(i/2)];  

        b=(unsigned char)(y+1.779*(u- 128));  
        g=(unsigned char)(y-0.7169*(v - 128)-0.3455*(u - 128));    
        r=(unsigned char)(y+ 1.4075*(v - 128));*/  
    }  
} 

四、RGB数据存储为图片

1、存储为BMP图片

请看另一篇博客，RGB TO BMP

2、存储为JPG图片

存储为JPG图片要用到一个开运库，libjpeg,或者libjpeg-turbo，我用的是libjpeg,网上关于这两个开源库的资料很多，可以从这个下载编译好的包，LIBJPEG包

封装的存储方法如下：

int rgb2jpeg(const char * filename, unsigned char* rgbData,int image_width,int image_height,int quality)  
{  
    struct jpeg_compress_struct jpeg;  //identify a compress object
    struct jpeg_error_mgr jerr;  //error information

    jpeg.err = jpeg_std_error(&jerr);  
    jpeg_create_compress(&jpeg);  //init compress object

    FILE* pFile;
    fopen_s(&pFile,filename,"wb" );  
    if( !pFile )  return 0;  
    jpeg_stdio_dest(&jpeg, pFile);  

    //compress param set,i just did a simple param set
    jpeg.client_data=(void*)&pFile;
    jpeg.image_width = image_width;  
    jpeg.image_height = image_height;  
    jpeg.input_components  = 3;  
    jpeg.in_color_space = JCS_RGB;   
    jpeg_set_defaults(&jpeg);   
     指定亮度及色度质量  
    jpeg.q_scale_factor[0] = jpeg_quality_scaling(100);  
    jpeg.q_scale_factor[1] = jpeg_quality_scaling(100);  
     图像采样率，默认为2 * 2  
    jpeg.comp_info[0].v_samp_factor = 2;  
    jpeg.comp_info[0].h_samp_factor = 2;  
     set jpeg compress quality  
    jpeg_set_quality(&jpeg, quality, TRUE);  //100 is the highest

    //start compress
    jpeg_start_compress(&jpeg, TRUE);  

    JSAMPROW row_pointer[1];  

    //from up to down ,set every pixel
    for( unsigned int i=0;i<jpeg.image_height;i++ )  
    {  
        row_pointer[0] = rgbData+i*jpeg.image_width*3;  
        jpeg_write_scanlines( &jpeg,row_pointer,1 );  
    }  
    //stop compress
    jpeg_finish_compress(&jpeg);  

    fclose( pFile );  
    pFile = NULL;  
    jpeg_destroy_compress(&jpeg);  
    return 0;  
}  

五、YUV数据存储为JPG

网上有不少关于YUV420数据存储为JPG的代码和博客，但是我用他们的代码，老是不成功，不是运行不起来，就是效果不好，不过还是表示万分感谢。

1、YUV420SP

int yuv420p_to_jpeg(const char * filename, const char* pdata,int image_width,int image_height, int quality){       struct jpeg_compress_struct cinfo;      struct jpeg_error_mgr jerr;      cinfo.err = jpeg_std_error(&jerr);      jpeg_create_compress(&cinfo);      FILE * outfile;    // target file      if ((outfile = fopen(filename, "wb")) == NULL) {          fprintf(stderr, "can't open %s\n", filename);          exit(1);      }      jpeg_stdio_dest(&cinfo, outfile);      cinfo.image_width = image_width;  // image width and height, in pixels      cinfo.image_height = image_height;      cinfo.input_components = 3;    // # of color components per pixel      cinfo.in_color_space = JCS_YCbCr;  //colorspace of input image      jpeg_set_defaults(&cinfo);      jpeg_set_quality(&cinfo, quality, TRUE );      //      //  cinfo.raw_data_in = TRUE;      cinfo.jpeg_color_space = JCS_YCbCr;      cinfo.comp_info[0].h_samp_factor = 2;      cinfo.comp_info[0].v_samp_factor = 2;      /      jpeg_start_compress(&cinfo, TRUE);      JSAMPROW row_pointer[1];    unsigned char *yuvbuf;    if((yuvbuf=(unsigned char *)malloc(image_width*3))!=NULL)        memset(yuvbuf,0,image_width*3);    unsigned char *ybase,*ubase;    ybase=pdata;    ubase=pdata+image_width*image_height;      int j=0;    while (cinfo.next_scanline < cinfo.image_height)     {        int idx=0;        for(int i=0;i<image_width;i++)        {             yuvbuf[idx++]=ybase[i + j * image_width];            yuvbuf[idx++]=ubase[j/2 * image_width+(i/2)*2];            yuvbuf[idx++]=ubase[j/2 * image_width+(i/2)*2+1];            }        row_pointer[0] = yuvbuf;        jpeg_write_scanlines(&cinfo, row_pointer, 1);        j++;    }    jpeg_finish_compress(&cinfo);      jpeg_destroy_compress(&cinfo);      fclose(outfile);      return 0;  }

2、YUV420P

其实YUV420P和YUV420SP主要区别就是取数据方式不同，前面对于YUV420P如何取数据已经讲得很清楚了，YUV420P存储为JPG只需要在上面YUV420SP存储为JPG的基础上改改取数据方法就好了。

效果：

这是一张1280X720的图片，大小385kb,因为是USB摄像头，所以图片质量感觉不是很高，总的来说效果不错！

六、YUV420SP 与 YUV420P相互转换

       知道了YUV420SP以及YUV420P的内存格式后，互相转换就不是难事了。

1、YUV420SP TO YUV420P

int yuv420sp_to_yuv420p(unsigned char * yuv420sp,unsigned char* yuv420p,int width,int height)
{
    if(yuv420sp==NULL)
        return;
    int i=0,j=0;
    //Y
    for(i=0;i<width*height;i++)
    {
        yuv420p[i]=yuv420sp[i];
    }
    //U
    for(int j=0,i=0;j<width*height/2;j+=2,i++)
    {
        yuv420p[i + width*height] = yuv420sp[j+width*height];
    }
    
    //V
    for(i=0,j=1,j<width*height/2;j+=2,i++)
    {
        yuv420p[i+width*height*5/4] = yuv420sp[j+width*height];
    }
}

2、YUV420P TO YUV420SP

int yuv420p_to_yuv420sp(unsigned char * yuv420p,unsigned char* yuv420sp,int width,int height)
{
    if(yuv420p==NULL)
        return;
    int i=0,j=0;
    //Y
    for(i=0;i<width*height;i++)
    {
        yuv420sp[i]=yuv420p[i];
    }

    int m=0,n=0;
    for(int j=0;j<width*height/2;j++)
    {
        if(j%2==0)
           yuv420sp[j+width*height]=yuv420p[m++];
        else
           yuv420sp[j+width*height]=yuv420p[n++];
    }
}

七、参考博客