YUYV转RGB-C-Cuda实现

介绍Cuda实现YUYV转RGB算法。

1.YUV介绍

  YUV是被欧洲电视系统所采用的一种颜色编码方法(属于PAL，Phase Alternation Line)，是PAL和SECAM模拟彩色电视制式采用的颜色空间。其中的Y、U、V几个字母不是英文单词的组合词，Y代表亮度，其实Y就是图像的灰度值；UV代表色差，U和V是构成彩色的两个分量。

1.1 YUV转RGB公式

YUV到RGB的转换有如下公式：

R = 1.164*(Y-16) + 1.159*(V-128); 
G = 1.164*(Y-16) - 0.380*(U-128)+ 0.813*(V-128); 
B = 1.164*(Y-16) + 2.018*(U-128));

那么YUYV(Y0UY1V)的实现就是使用Y0UV转换出一个RGB像素，使用Y1UV转换出第二个像素，那么就实现了四个字节转换出6个字节（2个RGB像素）。

2.代码实现

C语言实现：

void CPU_YUYV2RGB(char* arrOut, char* arrIn)
{
	unsigned char y0, y1, u, v;
	int r, g, b;
	int nIndex = 0;
	for(nIndex = 0; nIndex < N/2; nIndex++)
	{
		y0 = *(arrIn + nIndex*4);
		u = *(arrIn + nIndex*4 + 1);
		y1 = *(arrIn + nIndex*4 + 2);
		v = *(arrIn + nIndex*4 + 3);

		r = 1.164*(y0-16) + 1.159*(v-128);
		g = 1.164*(y0-16) - 0.380*(u-128) + 0.813*(v-128);
		b = 1.164*(y0-16) + 2.018*(u-128);

		if (r > 255) r = 255;
		if (g > 255) g = 255;
		if (b > 255) b = 255;
		if (r < 0) r = 0;
		if (g < 0) g = 0;
		if (b < 0) b = 0;

		*(arrOut + nIndex*6) = r;
		*(arrOut + nIndex*6+1) = g;
		*(arrOut + nIndex*6+2) = b;

		r = 1.164*(y1-16) + 1.159*(v-128);
		g = 1.164*(y1-16) - 0.380*(u-128) + 0.813*(v-128);
		b = 1.164*(y1-16) + 2.018*(u-128);

		if (r > 255) r = 255;
		if (g > 255) g = 255;
		if (b > 255) b = 255;
		if (r < 0) r = 0;
		if (g < 0) g = 0;
		if (b < 0) b = 0;

		*(arrOut + nIndex*6+3) = r;
		*(arrOut + nIndex*6+4) = g;
		*(arrOut + nIndex*6+5) = b;
	}
}

Cuda代码实现：

__global__ void YUYV2RGB(char *g_out, char *g_in, int N)
{
	unsigned int i = 0, j = 0;
	unsigned char y0, y1, u, v;
	int r, g, b;

    int nStart = blockIdx.x * 320 * 4 + threadIdx.x * 4 ;
    int nOut = blockIdx.x * 320 * 6 + threadIdx.x * 6 ;

    char *YUV = (char*)g_in + nStart;
    char* RGB = (char*)g_out + nOut;

    //for (i = 0, j = 0; i < (N << 1); i += 4, j += 6)
     //{
       y0 = (unsigned char)YUV[i + 0];
       u = (unsigned char)YUV[i + 1];
       y1 = (unsigned char)YUV[i + 2];
       v = (unsigned char)YUV[i + 3];

       r = 1.164*(y0-16) + 1.159*(v-128);
       g = 1.164*(y0-16) - 0.380*(u-128) + 0.813*(v-128);
       b = 1.164*(y0-16) + 2.018*(u-128);

       if (r > 255) r = 255;
       if (g > 255) g = 255;
       if (b > 255) b = 255;
       if (r < 0) r = 0;
       if (g < 0) g = 0;
       if (b < 0) b = 0;

       //YUV2RGB(y0, u, v, &r, &g, &b);
       RGB[j + 0] = r;
       RGB[j + 1] = g;
       RGB[j + 2] = b;
       //YUV2RGB(y1, u, v, &r, &g, &b);

       r = 1.164*(y1-16) + 1.159*(v-128);
       g = 1.164*(y1-16) - 0.380*(u-128) + 0.813*(v-128);
       b = 1.164*(y1-16) + 2.018*(u-128);

       if (r > 255) r = 255;
       if (g > 255) g = 255;
       if (b > 255) b = 255;
       if (r < 0) r = 0;
       if (g < 0) g = 0;
       if (b < 0) b = 0;

       RGB[j + 3] = r;
       RGB[j + 4] = g;
       RGB[j + 5] = b;
     //}
}