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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 <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.
// For those MCs that can be represented as kr and kb:
// Full range
// float M[3][3]
// {{1,0,2*(1-kr)},{1,-((2*kb)/((2-kb)*(1-kb-kr))),-((2*kr)/((2-kr)*(1-kb-kr)))},{1,2*(1-kb),0}};
// float B[3]
// {1+(256*(1-kr))/255,1-(256*kb)/(255*(2-kb)*(1-kb-kr))-(256*kr)/(255*(2-kr)*(1-kb-kr)),1+(256*(1-kb))/255};
// Limited range
// float M[3][3]
// {{85/73,0,255/112-(255*kr)/112},{85/73,-((255*kb)/(112*(2-kb)*(1-kb-kr))),-((255*kr)/(112*(2-kr)*(1-kb-kr)))},{85/73,255/112-(255*kb)/112,0}};
// float B[3]
// {77662/43435-(1537*kr)/1785,203/219-(1537*kb)/(1785*(2-kb)*(1-kb-kr))-(1537*kr)/(1785*(2-kr)*(1-kb-kr)),77662/43435-(1537*kb)/1785};
// mc bt
// 1 bt.709 KR = 0.2126; KB = 0.0722
// 4 fcc KR = 0.30; KB = 0.11
// 6 bt.601 KR = 0.299; KB = 0.114
// 7 SMPTE 240M KR = 0.212; KB = 0.087
// 10 bt2020 KR = 0.2627; KB = 0.0593
// 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
// https://mymusing.co/bt601-yuv-to-rgb-conversion-color/
// // 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 round(float v) {
return (int)(v + 0.5);
}
int main(int argc, const char* argv[]) {
if (argc < 2) {
printf("color kr kb\n");
return -1;
}
float kr = atof(argv[1]);
float kb = 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 %-3d /* round(%f * 64) */\n", round(ub * 64), ub);
printf("UG %-3d /* round(%f * 64) */\n", round(ug * 64), ug);
printf("VG %-3d /* round(%f * 64) */\n", round(vg * 64), vg);
printf("VR %-3d /* round(%f * 64) */\n", round(vr * 64), vr);
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("Limited 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 %-3d /* round(%f * 64) */\n", round(ub * 64), ub);
printf("UG %-3d /* round(%f * 64) */\n", round(ug * 64), ug);
printf("VG %-3d /* round(%f * 64) */\n", round(vg * 64), vg);
printf("VR %-3d /* round(%f * 64) */\n", round(vr * 64), vr);
return 0;
}
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