跟雷神学音视频-6.YUV像素数据处理

分离YUV420P

int yuv420pSplit(char *url,int w,int h,int num){
    unsigned char *pic=(unsigned char *)malloc(w*h*3/2);
    FILE *fp=fopen(url,"rb+");
    
    for(int i=0;i<num;i++){
        fread(pic,1,w*h*3/2,fp);
        
        pic;//Y w*h
        pic+w*h;//U w*h/4
        pic+w*h*5/4;//V w*h/4
    }
    free(pic);
    close(fp);
    
    return 0;
}

分离YUV444P

int yuv444Split(char *url,int w,int h,int num){
    unsigned char *pic=(unsigned char *)malloc(w*h*3);
    FILE *fp=fopen(url,"rb+");
    
    for(int i=0;i<num;i++){
        fread(pic,1,w*h*3,fp);
        
        pic;//Y w*h
        pic+w*h;//U w*h
        pic+w*h*2;//V w*h
    }
    free(pic);
    close(fp);
    
    return 0;
}

去掉YUV420P的颜色

int yuv420Gray(char *url,int w,int h,int num){
    unsigned char *pic=(unsigned char *)malloc(w*h*3/2);
    FILE *fp=fopen(url,"rb+");
    
    for(int i=0;i<num;i++){
        fread(pic,1,w*h*3/2,fp);
        memset(pic+w*h,128,w*h/2);
        
        //色度分量在偏置处理前的取值范围是-128至127,此时无色对应0。经偏置后变成0-255，此时无色对应为128
        //因此只需要将U V设置成128
    }
    free(pic);
    close(fp);
    
    return 0;
}

YUV的PSNR计算

PSNR是最基本的视频质量评价方法，

RGB2BMP

BMP文件是由BITMAPFILEHEADER、BITMAPINFOHEADER、BGR像素数据共3个部分构成，它的结构如下图所示

typedef  struct  tagBITMAPFILEHEADER
{ 
unsigned short int  bfType;       //位图文件的类型，必须为BM 
unsigned long       bfSize;       //文件大小，以字节为单位
unsigned short int  bfReserverd1; //位图文件保留字，必须为0 
unsigned short int  bfReserverd2; //位图文件保留字，必须为0 
unsigned long       bfbfOffBits;  //位图文件头到数据的偏移量，以字节为单位
}BITMAPFILEHEADER; 
typedef  struct  tagBITMAPINFOHEADER 
{ 
long biSize;                        //该结构大小，字节为单位
long  biWidth;                     //图形宽度以象素为单位
long  biHeight;                     //图形高度以象素为单位
short int  biPlanes;               //目标设备的级别，必须为1 
short int  biBitcount;             //颜色深度，每个象素所需要的位数
short int  biCompression;        //位图的压缩类型
long  biSizeImage;              //位图的大小，以字节为单位
long  biXPelsPermeter;       //位图水平分辨率，每米像素数
long  biYPelsPermeter;       //位图垂直分辨率，每米像素数
long  biClrUsed;            //位图实际使用的颜色表中的颜色数
long  biClrImportant;       //位图显示过程中重要的颜色数
}BITMAPINFOHEADER;

void RGB2BMP(const char * rgbUrl,int width,int height,const char * bmpUrl){
    int i=0,j=0;
	BITMAPFILEHEADER m_BMPHeader={0};
	BITMAPINFOHEADER  m_BMPInfoHeader={0};
	char bfType[2]={'B','M'};
	int header_size=sizeof(bfType)+sizeof(BITMAPFILEHEADER)+sizeof(BITMAPINFOHEADER);
	unsigned char *rgb24_buffer=(unsigned char *)malloc(width*height*3);
    
    FILE *fp_rgb24=fopen(rgb24path,"rb"),*fp_bmp=fopen(bmppath,"wb");
	fread(rgb24_buffer,1,width*height*3,fp_rgb24);
    
    m_BMPHeader.bfSize=3*width*height+header_size;
	m_BMPHeader.bfbfOffBits=header_size;
 
	m_BMPInfoHeader.biSize=sizeof(InfoHead); 
	m_BMPInfoHeader.biWidth=width;
	//BMP storage pixel data in opposite direction of Y-axis (from bottom to top).
	m_BMPInfoHeader.biHeight=-height;
	m_BMPInfoHeader.biPlanes=1;
	m_BMPInfoHeader.biBitcount=24;
	m_BMPInfoHeader.biSizeImage=3*width*height;
    
    fwrite(bfType,1,sizeof(bfType),fp_bmp);
	fwrite(&m_BMPHeader,1,sizeof(m_BMPHeader),fp_bmp);
	fwrite(&m_BMPInfoHeader,1,sizeof(m_BMPInfoHeader),fp_bmp);
    
    //BMP save R1|G1|B1,R2|G2|B2 as B1|G1|R1,B2|G2|R2
	//It saves pixel data in Little Endian
	//So we change 'R' and 'B'
	for(j =0;j<height;j++){
		for(i=0;i<width;i++){
			char temp=rgb24_buffer[(j*width+i)*3+2];
			rgb24_buffer[(j*width+i)*3+2]=rgb24_buffer[(j*width+i)*3+0];
			rgb24_buffer[(j*width+i)*3+0]=temp;
		}
	}
	fwrite(rgb24_buffer,3*width*height,1,fp_bmp);
	fclose(fp_rgb24);
	fclose(fp_bmp);
	free(rgb24_buffer);
    
    return 0;
}

RGB2YUV420P

int RGB2YUV420P(unsigned char *rgbBuf,int w,int h,unsigned char *yuvBuf){
    memset(yuvBuf,0,w*h*3/2);
    unsigned char *pY,*pU,*pV,*pRGB;
    
    pY=yuvBuf;
    pU=yuvBuf+w*h;
    pV=yuvBuf+w*h*5/4;
    
    unsigned char y,u,v,r,g,b;
	for (int j = 0; j<h;j++){
		pRGB = rgbBuf + w*j*3 ;
		for (int i = 0;i<w;i++){
			
			r = *(pRGB++);
			g = *(pRGB++);
			b = *(pRGB++);
			y = (unsigned char)( ( 66 * r + 129 * g +  25 * b + 128) >> 8) + 16  ;       
			u = (unsigned char)( ( -38 * r -  74 * g + 112 * b + 128) >> 8) + 128 ;       
			v = (unsigned char)( ( 112 * r -  94 * g -  18 * b + 128) >> 8) + 128 ;
            
            //过滤一下y u v的大小 确保在0~255
            
			*(pY++) = y;
			if (j%2==0&&i%2 ==0){
				*(pU++) =u;
			}else{
				if (i%2==0){
					*(pV++) =v;
				}
			}
		}

        return 0;
}
    /*
Y= 0.299*R+0.587*G+0.114*B
U=-0.147*R-0.289*G+0.463*B
V= 0.615*R-0.515*G-0.100*B
    */