How to deal with RGB to YUV conversion

The formula says:

Y = 0.299 * R + 0.587 * G + 0.114 * B;

U = -0.14713 * R - 0.28886 * G + 0.436 * B;

V = 0.615 * R - 0.51499 * G - 0.10001 * B;

What if, for example, the U variabl开发者_高级运维e becomes negative?

U = -0.14713 * R - 0.28886 * G + 0.436 * B;

Assume maximum values for R and G (ones) and B = 0 So, I am interested in implementing this convetion function in OpenCV, So, how to deal with negative values? Using float image? anyway please explain me, may be I don't understand something..

Y, U and V are all allowed to be negative when represented by decimals, according to the YUV color plane.

You can convert RGB<->YUV in OpenCV with cvtColor using the code CV_YCrCb2RGB for YUV->RGB and CV_RGBYCrCb for RGB->YUV.

void cvCvtColor(const CvArr* src, CvArr* dst, int code)

Converts an image from one color space to another.

for planar formats OpenCV is not the right tool for the job. Instead you are better off using ffmpeg. for example

static void rgbToYuv(byte* src, byte* dst, int width,int height)
{

    byte* src_planes[3] = {src,src + width*height, src+ (width*height*3/2)};
    int src_stride[3] = {width, width / 2, width / 2};
    byte* dest_planes[3] = {dst,NULL,NULL};
    int dest_stride[3] = {width*4,0,0};
    struct SwsContext *img_convert_ctx = sws_getContext(
        width,height,
        PIX_FMT_YUV420P,width,height,PIX_FMT_RGB32,SWS_POINT,NULL,NULL,NULL);
        sws_scale(img_convert_ctx, src_planes,src_stride,0,height,dest_planes,dest_stride); 
    sws_freeContext(img_convert_ctx);
}

will convert a YUV420 image to RGB32