C语言 将 RGB 转换为 YCbCr - C 代码
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/7086820/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
Convert RGB to YCbCr - C code
提问by Vinicius Garcia
I need to convert RGB to YCbCr for my final project and I trying to do this way (I'm programming in C):
我需要为我的最终项目将 RGB 转换为 YCbCr，我尝试这样做（我正在用 C 编程）：
/* Autor: Vinicius Garcia
* Data : 09.ago.2011
*
* Fun??o que converte um pixel RGB em YCbCr
*
* param : int R valor do pixel no canal red
* param : int G valor do pixel no canal green
* param : int B valor do pixel no canal blue
* return: int* vetor de inteiros com os valores H, S e V calculados - nesta ordem
*/
int* converter_RGB_para_YCbCr(int R, int G, int B){
int* YCbCr = (int*) malloc(3 * sizeof(int));
double delta = 128.0; //Constante necessaria para o calculo da convers?o de cor
double Y = (0.299 * R + 0.587 * G + 0.114 * B);
double Cb = ((B - Y) * 0.564 + delta);
double Cr = ((R - Y) * 0.713 + delta);
YCbCr[0] = (int) Y;
YCbCr[1] = (int) Cb;
YCbCr[2] = (int) Cr;
return YCbCr;
}
But it doesn't work for me!
但这对我不起作用！
I was comparing with cvCvtColor (from OpenCv library) and the results doesn't match:
我正在与 cvCvtColor （来自 OpenCv 库）进行比较，结果不匹配：
R = 88, G = 76, B = 78
cvCvtColor: Y = 80, Cb = 127, Cr = 134
myfunction: Y = 382, Cb = 132, Cr = 132 (cr and cr are always equal!)
I really need help with this, I trying do this for a long time and I couldn't find any answer for my doubt.
我真的需要这方面的帮助，我尝试这样做了很长时间，但找不到任何答案来解决我的疑问。
Do you guys think I'm getting the RGB values wrong? I'm doing this way:
你们认为我把RGB值弄错了吗？我这样做：
uchar B = CV_IMAGE_ELEM(img_RGB, uchar, linha, coluna * 3);
uchar G = CV_IMAGE_ELEM(img_RGB, uchar, linha, coluna * 3 + 1);
uchar R = CV_IMAGE_ELEM(img_RGB, uchar, linha, coluna * 3 + 2);
Then I'm calling my conversion function this way:
然后我以这种方式调用我的转换函数：
converter_RGB_para_YCbCr(R, G, B);
My function expects int R, int G, int B but I'm passing uchar B, uchar G, uchar R. its that ok?
我的函数需要 int R、int G、int B，但我正在传递 uchar B、uchar G、uchar R。它可以吗？
回答by Russ Clarke
int y = (int)( 0.299 * R + 0.587 * G + 0.114 * B);
int cb = (int)(-0.16874 * R - 0.33126 * G + 0.50000 * B);
int cr = (int)( 0.50000 * R - 0.41869 * G - 0.08131 * B);
回答by Geomorillo
you should use this formula matlab uses it
你应该使用这个公式 matlab 使用它
Y = 0.257R′ + 0.504G′ + 0.098B′ + 16
Y = 0.257R' + 0.504G' + 0.098B' + 16
Cb = -0.148R′ - 0.291G′ + 0.439B′ + 128
Cb = -0.148R' - 0.291G' + 0.439B' + 128
Cr = 0.439R′ - 0.368G′ - 0.071B′ + 128
Cr = 0.439R' - 0.368G' - 0.071B' + 128
and to rgb
和 rgb
R′ = 1.164(Y - 16) + 1.596(Cr - 128)
R' = 1.164(Y - 16) + 1.596(Cr - 128)
G′ = 1.164(Y - 16) - 0.813(Cr - 128) - 0.392(Cb - 128)
G′ = 1.164(Y - 16) - 0.813(Cr - 128) - 0.392(Cb - 128)
B′ = 1.164(Y - 16) + 2.017(Cb - 128)
B' = 1.164(Y - 16) + 2.017(Cb - 128)
I have tested them in a software im making they work ok
我已经在软件中对它们进行了测试，使它们可以正常工作
