How to deal with RGB to YUV conversion
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04-10-2019 - |
Question
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 variable 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..
Solution
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.
OTHER TIPS
Y, U and V are all allowed to be negative when represented by decimals, according to the YUV color plane.
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