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/*
* Copyright 2021 The LibYuv Project Authors. All rights reserved.
*
* Use of this source code is governed by a BSD-style license
* that can be found in the LICENSE file in the root of the source
* tree. An additional intellectual property rights grant can be found
* in the file PATENTS. All contributing project authors may
* be found in the AUTHORS file in the root of the source tree.
*/
#include <math.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
// This utility computes values needed to generate yuvconstants based on
// white point values.
// The yuv formulas are tuned for 8 bit YUV channels.
// See Also
// https://mymusing.co/bt601-yuv-to-rgb-conversion-color/
// BT.709 full range YUV to RGB reference
// R = Y + V * 1.5748
// G = Y - U * 0.18732 - V * 0.46812
// B = Y + U * 1.8556
// KR = 0.2126
// KB = 0.0722
// // Y contribution to R,G,B. Scale and bias.
// #define YG 16320 /* round(1.000 * 64 * 256 * 256 / 257) */
// #define YB 32 /* 64 / 2 */
//
// // U and V contributions to R,G,B.
// #define UB 113 /* round(1.77200 * 64) */
// #define UG 22 /* round(0.34414 * 64) */
// #define VG 46 /* round(0.71414 * 64) */
// #define VR 90 /* round(1.40200 * 64) */
//
// // Bias values to round, and subtract 128 from U and V.
// #define BB (-UB * 128 + YB)
// #define BG (UG * 128 + VG * 128 + YB)
// #define BR (-VR * 128 + YB)
int main(int argc, const char* argv[]) {
if (argc < 3) {
printf("yuvconstants [KR] [KB]\n");
printf(" e.g. yuvconstants 0.2126 0.0722\n");
printf(" MC BT KR KB\n");
printf(" 1 BT.709 KR = 0.2126; KB = 0.0722\n");
printf(" 4 FCC KR = 0.30; KB = 0.11\n");
printf(" 6 BT.601 KR = 0.299; KB = 0.114\n");
printf(" 7 SMPTE 240M KR = 0.212; KB = 0.087\n");
printf(" 9 BT.2020 KR = 0.2627; KB = 0.0593\n");
return -1;
}
float kr = (float)atof(argv[1]);
float kb = (float)atof(argv[2]);
float kg = 1 - kr - kb;
float vr = 2 * (1 - kr);
float ug = 2 * ((1 - kb) * kb / kg);
float vg = 2 * ((1 - kr) * kr / kg);
float ub = 2 * (1 - kb);
printf("Full range\n");
printf("R = Y + V * %5f\n", vr);
printf("G = Y - U * %6f - V * %6f\n", ug, vg);
printf("B = Y + U * %5f\n", ub);
printf("KR = %4f; ", kr);
printf("KB = %4f\n", kb);
// printf("KG = %4f\n", kg);
// #define YG 16320 /* round(1.000 * 64 * 256 * 256 / 257) */
// #define YB 32 /* 64 / 2 */
//
// // U and V contributions to R,G,B.
printf("UB %-3.0f /* round(%f * 64 = %8.4f) */\n", round(ub * 64), ub, ub * 64);
printf("UG %-3.0f /* round(%f * 64 = %8.4f) */\n", round(ug * 64), ug, ug * 64);
printf("VG %-3.0f /* round(%f * 64 = %8.4f) */\n", round(vg * 64), vg, vg * 64);
printf("VR %-3.0f /* round(%f * 64 = %8.4f) */\n", round(vr * 64), vr, vr * 64);
vr = 255.f / 224.f * 2 * (1 - kr);
ug = 255.f / 224.f * 2 * ((1 - kb) * kb / kg);
vg = 255.f / 224.f * 2 * ((1 - kr) * kr / kg);
ub = 255.f / 224.f * 2 * (1 - kb);
printf("\nLimited range\n");
printf("R = (Y - 16) * 1.164 + V * %5f\n", vr);
printf("G = (Y - 16) * 1.164 - U * %6f - V * %6f\n", ug, vg);
printf("B = (Y - 16) * 1.164 + U * %5f\n", ub);
// printf("KG = %4f\n", kg);
// #define YG 16320 /* round(1.000 * 64 * 256 * 256 / 257) */
// #define YB 32 /* 64 / 2 */
//
// // U and V contributions to R,G,B.
printf("UB %-3.0f /* round(%f * 64 = %8.4f) */\n", round(ub * 64), ub, ub * 64);
printf("UG %-3.0f /* round(%f * 64 = %8.4f) */\n", round(ug * 64), ug, ug * 64);
printf("VG %-3.0f /* round(%f * 64 = %8.4f) */\n", round(vg * 64), vg, vg * 64);
printf("VR %-3.0f /* round(%f * 64 = %8.4f) */\n", round(vr * 64), vr, vr * 64);
return 0;
}
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