【video】YUV420P转换为RGB32格式-USB迷|专注于互联网分享

【video】YUV420P转换为RGB32格式

从网络摄像机中获取的帧数据是YUV420P格式的，而我们处理图像需要RGB格式，在网上找了一段将YUV420P格式的帧转换为RGB的代码。

<方法一> 直接计算，效率低

[cpp] view plaincopy
// 转换 YV12 到 RGB24
// pYUV 的大小 (3 * iWidth * iHeight / 2)
// pRGB 的大小 (3 * iWidth * iHeight)
// 如果成功返回 true, 否则 false
bool YV12_to_RGB24(unsigned char* pYV12, unsigned char* pRGB24, int iWidth, int iHeight)
{
if(!pYV12 || !pRGB24)
return false;

const long nYLen = long(iHeight * iWidth);
const int nHfWidth = (iWidth>>1);

if(nYLen<1 || nHfWidth<1)
return false;

// yv12数据格式，其中Y分量长度为width * height, U和V分量长度都为width * height / 4
// |WIDTH |
// y…y--------
// y…y HEIGHT
// y…y
// y…y--------
// v…v
// v…v
// u…u
// u…u
unsigned char* yData = pYV12;
unsigned char* vData = &yData[nYLen];
unsigned char* uData = &vData[nYLen>>2];

if(!uData || !vData)
return false;

// Convert YV12 to RGB24
//
// formula
// [1 1 1 ]
// [r g b] = [y u-128 v-128] [0 0.34375 0 ]
// [1.375 0.703125 1.734375]
// another formula
// [1 1 1 ]
// [r g b] = [y u-128 v-128] [0 0.698001 0 ]
// [1.370705 0.703125 1.732446]
int rgb[3];
int i, j, m, n, x, y;
m = -iWidth;
n = -nHfWidth;
for(y=0; y < iHeight; y++)
{
m += iWidth;
if(!(y % 2))
n += nHfWidth;
for(x=0; x < iWidth; x++)
{
i = m + x;
j = n + (x>>1);
rgb[2] = int(yData[i] + 1.370705 * (vData[j] - 128)); // r分量值
rgb[1] = int(yData[i] - 0.698001 * (uData[j] - 128) - 0.703125 * (vData[j] - 128)); // g分量值
rgb[0] = int(yData[i] + 1.732446 * (uData[j] - 128)); // b分量值

j = nYLen - iWidth - m + x;
i = (j<<1) + j;
for(j=0; j<3; j++)
{
if(rgb[j]>=0 && rgb[j]<=255)
pRGB24[i + j] = rgb[j];
else
pRGB24[i + j] = (rgb[j] < 0) ? 0 : 255;
}
}
}
return true;
}

在利用OpenCV进行处理时，如果直接将转换好的数据赋给IplImage->imageData，会出现红蓝通道对调的情况，因为OpenCV中默认使用的是BGR的排列方式。
将代码中的给rgb复制的一段稍微改一下就行，改为：

[cpp] view plaincopy
rgb[0] = int(yData[i] + 1.370705 * (vData[j] - 128)); // r分量值
rgb[1] = int(yData[i] - 0.698001 * (uData[j] - 128) - 0.703125 * (vData[j] - 128)); // g分量值
rgb[2] = int(yData[i] + 1.732446 * (uData[j] - 128)); // b分量值

<方法二>查表，效率高

[cpp] view plaincopy
#include
#include <string.h>
using namespace std;

static long int crv_tab[256];
static long int cbu_tab[256];
static long int cgu_tab[256];
static long int cgv_tab[256];
static long int tab_76309[256];
static unsigned char clp[1024]; //for clip in CCIR601

void InitConvtTbl();
void YUV2RGB420(unsigned char *src, unsigned char *dst_ori,
int width,int height);

//
/ Sum the input /
/ Input: input, len /
/ Output: input /
/ Algorithm: add /
//
void InitConvtTbl()
{
long int crv,cbu,cgu,cgv;
int i,ind;

crv   =   104597;   cbu   =   132201;     /*   fra   matrise   i   global.h   */   
cgu   =   25675;     cgv   =   53279;   for   (i   =   0;   i   <   256;   i++)   {   crv_tab[i]   =   (i-128)   *   crv;   cbu_tab[i]   =   (i-128)   *   cbu;   cgu_tab[i]   =   (i-128)   *   cgu;   cgv_tab[i]   =   (i-128)   *   cgv;   tab_76309[i]   =   76309*(i-16);   
}   for   (i=0;   i <384;   i++)   clp[i]   =0;   
ind=384;   
for   (i=0;i <256;   i++)   clp[ind++]=i;   
ind=640;   
for   (i=0;i <384;i++)   clp[ind++]=255;

}

void YUV2RGB420(unsigned char *src, unsigned char *dst_ori,
int width,int height)
{
unsigned char *src0;
unsigned char *src1;
unsigned char *src2;
int y1,y2,u,v;
unsigned char *py1,*py2;
int i,j, c1, c2, c3, c4;
unsigned char *d1, *d2, *d3;

//Initialization   
src0=src;   
src1=src+width*height;   
src2=src+width*height+width*height/4;   py1=src0;   
py2=py1+width;   
d1=dst_ori + 3 * width * (height -1);   
d2=d1-3*width;   
for   (j   =   0;   j   <   height;   j   +=   2)   {     for   (i   =   0;   i   <   width;   i   +=   2)   {   u   =   *src1++;   v   =   *src2++;   c1   =   crv_tab[v];   c2   =   cgu_tab[u];   c3   =   cgv_tab[v];   c4   =   cbu_tab[u];   //up-left   y1   =   tab_76309[*py1++];   *d1++   =   clp[384+((y1   +   c4)>> 16)];       *d1++   =   clp[384+((y1   -   c2   -   c3)>> 16)];   *d1++   =   clp[384+((y1   +   c1)>> 16)];   //down-left   y2   =   tab_76309[*py2++];   *d2++   =   clp[384+((y2   +   c4)>> 16)];       *d2++   =   clp[384+((y2   -   c2   -   c3)>> 16)];   *d2++   =   clp[384+((y2   +   c1)>> 16)];   //up-right   y1   =   tab_76309[*py1++];   *d1++   =   clp[384+((y1   +   c4)>> 16)];       *d1++   =   clp[384+((y1   -   c2   -   c3)>> 16)];   *d1++   =   clp[384+((y1   +   c1)>> 16)];   //down-right   y2   =   tab_76309[*py2++];   *d2++   =   clp[384+((y2   +   c4)>> 16)];       *d2++   =   clp[384+((y2   -   c2   -   c3)>> 16)];   *d2++   =   clp[384+((y2   +   c1)>> 16)];   }   d1   -=   3*width * 3;   d2   -=   3*width * 3;   py1+=       width;   py2+=       width;   
}

}