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How to perform RGB->YUV conversion in C/C++?
I have some Bitmap.. RGB I need to convert it to YUV
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The relation between data rate and sampling (A:B:C) is defined by the ratio between Y to U and V channel. To convert from RGB to YUV or back, it is simplest to use RGB888 and YUV444. For YUV411, YUV422 and YUV420, the bytes need to be converted to YUV444 first.
YUV color-spaces are a more efficient coding and reduce the bandwidth more than RGB capture can. Most video cards, therefore, render directly using YUV or luminance/chrominance images. The most important component for YUV capture is always the luminance, or Y component.
V = 0.615 * R - 0.51499 * G - 0.10001 * B; figure(7),imshow(V); YUV = cat(3,Y,U,V); figure(8),imshow(YUV);
You might also want to try these integer only calculations (should be faster than floats)
#define CLIP(X) ( (X) > 255 ? 255 : (X) < 0 ? 0 : X)
// RGB -> YUV
#define RGB2Y(R, G, B) CLIP(( ( 66 * (R) + 129 * (G) + 25 * (B) + 128) >> 8) + 16)
#define RGB2U(R, G, B) CLIP(( ( -38 * (R) - 74 * (G) + 112 * (B) + 128) >> 8) + 128)
#define RGB2V(R, G, B) CLIP(( ( 112 * (R) - 94 * (G) - 18 * (B) + 128) >> 8) + 128)
// YUV -> RGB
#define C(Y) ( (Y) - 16 )
#define D(U) ( (U) - 128 )
#define E(V) ( (V) - 128 )
#define YUV2R(Y, U, V) CLIP(( 298 * C(Y) + 409 * E(V) + 128) >> 8)
#define YUV2G(Y, U, V) CLIP(( 298 * C(Y) - 100 * D(U) - 208 * E(V) + 128) >> 8)
#define YUV2B(Y, U, V) CLIP(( 298 * C(Y) + 516 * D(U) + 128) >> 8)
// RGB -> YCbCr
#define CRGB2Y(R, G, B) CLIP((19595 * R + 38470 * G + 7471 * B ) >> 16)
#define CRGB2Cb(R, G, B) CLIP((36962 * (B - CLIP((19595 * R + 38470 * G + 7471 * B ) >> 16) ) >> 16) + 128)
#define CRGB2Cr(R, G, B) CLIP((46727 * (R - CLIP((19595 * R + 38470 * G + 7471 * B ) >> 16) ) >> 16) + 128)
// YCbCr -> RGB
#define CYCbCr2R(Y, Cb, Cr) CLIP( Y + ( 91881 * Cr >> 16 ) - 179 )
#define CYCbCr2G(Y, Cb, Cr) CLIP( Y - (( 22544 * Cb + 46793 * Cr ) >> 16) + 135)
#define CYCbCr2B(Y, Cb, Cr) CLIP( Y + (116129 * Cb >> 16 ) - 226 )
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