avutil/colorspace: add macros for RGB->YUV BT.709

libavutil/colorspace.h

@@ -119,4 +119,32 @@ static inline int C_JPEG_TO_CCIR(int y) {
 (((FIX(0.50000) * r1 - FIX(0.41869) * g1 - \
    FIX(0.08131) * b1 + (ONE_HALF) - 1) >> (SCALEBITS)) + 128)
 
+// Conversion macros for 8-bit RGB to YUV
+// Derived from ITU-R BT.709-6 (06/2015) Item 3.5
+// https://www.itu.int/rec/R-REC-BT.709-6-201506-I/en
+
+#define RGB_TO_Y_BT709(r, g, b) \
+((FIX(0.21260*219.0/255.0) * (r) + FIX(0.71520*219.0/255.0) * (g) + \
+  FIX(0.07220*219.0/255.0) * (b) + (ONE_HALF + (16 << SCALEBITS))) >> SCALEBITS)
+
+#define RGB_TO_U_BT709(r1, g1, b1, shift)\
+(((- FIX(0.11457*224.0/255.0) * r1 - FIX(0.38543*224.0/255.0) * g1 +         \
+     FIX(0.50000*224.0/255.0) * b1 + (ONE_HALF << shift) - 1) >> (SCALEBITS + shift)) + 128)
+
+#define RGB_TO_V_BT709(r1, g1, b1, shift)\
+(((FIX(0.50000*224.0/255.0) * r1 - FIX(0.45415*224.0/255.0) * g1 -           \
+   FIX(0.04585*224.0/255.0) * b1 + (ONE_HALF << shift) - 1) >> (SCALEBITS + shift)) + 128)
+
+#define RGB_TO_Y_BT709_FULL(r, g, b) \
+(FFMIN((FIX(0.21260) * (r) + FIX(0.71520) * (g) + \
+  FIX(0.07220) * (b) + (ONE_HALF)) >> SCALEBITS, 255))
+
+#define RGB_TO_U_BT709_FULL(r1, g1, b1)\
+(((- FIX(0.11457) * r1 - FIX(0.38543) * g1 + \
+     FIX(0.50000) * b1 + (ONE_HALF) - 1) >> (SCALEBITS)) + 128)
+
+#define RGB_TO_V_BT709_FULL(r1, g1, b1)\
+(((FIX(0.50000) * r1 - FIX(0.45415) * g1 - \
+   FIX(0.04585) * b1 + (ONE_HALF) - 1) >> (SCALEBITS)) + 128)
+
 #endif /* AVUTIL_COLORSPACE_H */