From 637ec35d6a28f3d9e08acc0c1305ed0c2436f5f4 Mon Sep 17 00:00:00 2001
From: Thomas Harte <thomas.harte@gmail.com>
Date: Tue, 11 Aug 2020 19:58:57 -0400
Subject: [PATCH] Adds getters for standard colour-space conversion matrices.

These are just more details on the meaning of the colour spaces, so I think they belong here.
---
 Outputs/ScanTarget.hpp | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/Outputs/ScanTarget.hpp b/Outputs/ScanTarget.hpp
index b8f5858ae..92899e0c3 100644
--- a/Outputs/ScanTarget.hpp
+++ b/Outputs/ScanTarget.hpp
@@ -9,6 +9,7 @@
 #ifndef Outputs_Display_ScanTarget_h
 #define Outputs_Display_ScanTarget_h
 
+#include <array>
 #include <cstddef>
 #include <cstdint>
 #include "../ClockReceiver/TimeTypes.hpp"
@@ -153,6 +154,34 @@ constexpr inline DisplayType natural_display_type_for_data_type(InputDataType da
 	}
 }
 
+/// @returns A 3x3 matrix in row-major order to convert from @c colour_space to RGB.
+inline std::array<float, 9> to_rgb_matrix(ColourSpace colour_space) {
+	const std::array<float, 9> yiq_to_rgb = {1.0f, 1.0f, 1.0f, 0.956f, -0.272f, -1.106f, 0.621f, -0.647f, 1.703f};
+	const std::array<float, 9> yuv_to_rgb = {1.0f, 1.0f, 1.0f, 0.0f, -0.39465f, 2.03211f, 1.13983f, -0.58060f, 0.0f};
+
+	switch(colour_space) {
+		case ColourSpace::YIQ:	return yiq_to_rgb;
+		case ColourSpace::YUV:	return yuv_to_rgb;
+	}
+
+	// Should be unreachable.
+	return std::array<float, 9>{};
+}
+
+/// @returns A 3x3 matrix in row-major order to convert to @c colour_space to RGB.
+inline std::array<float, 9> from_rgb_matrix(ColourSpace colour_space) {
+	const std::array<float, 9> rgb_to_yiq = {0.299f, 0.596f, 0.211f, 0.587f, -0.274f, -0.523f, 0.114f, -0.322f, 0.312f};
+	const std::array<float, 9> rgb_to_yuv = {0.299f, -0.14713f, 0.615f, 0.587f, -0.28886f, -0.51499f, 0.114f, 0.436f, -0.10001f};
+
+	switch(colour_space) {
+		case ColourSpace::YIQ:	return rgb_to_yiq;
+		case ColourSpace::YUV:	return rgb_to_yuv;
+	}
+
+	// Should be unreachable.
+	return std::array<float, 9>{};
+}
+
 /*!
 	Provides an abstract target for 'scans' i.e. continuous sweeps of output data,
 	which are identified by 2d start and end coordinates, and the PCM-sampled data