rgb2yuv.h

/**************************************************************************/
/*  rgb2yuv.h                                                             */
/**************************************************************************/
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/* Copyright (c) 2007-2014 Juan Linietsky, Ariel Manzur.                  */
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#pragma once

#include "core/typedefs.h"

// For reference, see:
// - https://stackoverflow.com/a/9467305
// - https://en.wikipedia.org/wiki/YCbCr#Approximate_8-bit_matrices_for_BT.601

static void _rgb2yuv420(uint8_t *y, uint8_t *u, uint8_t *v, uint8_t *rgb, size_t width, size_t height, size_t pixel_size) {
	size_t uvpos = 0;
	size_t i = 0;
	for (size_t line = 0; line < height; line += 2) {
		for (size_t x = 0; x < width; x += 2) {
			uint8_t r = rgb[pixel_size * i];
			uint8_t g = rgb[pixel_size * i + 1];
			uint8_t b = rgb[pixel_size * i + 2];

			y[i++] = ((66 * r + 129 * g + 25 * b) >> 8) + 16;

			u[uvpos] = ((-38 * r + -74 * g + 112 * b) >> 8) + 128;
			v[uvpos] = ((112 * r + -94 * g + -18 * b) >> 8) + 128;
			uvpos++;

			r = rgb[pixel_size * i];
			g = rgb[pixel_size * i + 1];
			b = rgb[pixel_size * i + 2];

			y[i++] = ((66 * r + 129 * g + 25 * b) >> 8) + 16;
		}
		for (size_t x = 0; x < width; x += 1) {
			uint8_t r = rgb[pixel_size * i];
			uint8_t g = rgb[pixel_size * i + 1];
			uint8_t b = rgb[pixel_size * i + 2];

			y[i++] = ((66 * r + 129 * g + 25 * b) >> 8) + 16;
		}
	}
}

static void rgb2yuv420(uint8_t *y, uint8_t *u, uint8_t *v, uint8_t *rgb, size_t width, size_t height) {
	_rgb2yuv420(y, u, v, rgb, width, height, 3);
}

static void rgba2yuv420(uint8_t *y, uint8_t *u, uint8_t *v, uint8_t *rgba, size_t width, size_t height) {
	_rgb2yuv420(y, u, v, rgba, width, height, 4);
}