From 83a064ddc1156b4d66ff8551b7c639b6432f9dd8 Mon Sep 17 00:00:00 2001
From: BlackMark <me@blackmark.me>
Date: Sun, 29 May 2022 18:45:46 +0200
Subject: [PATCH] Implement multi-channel run length encoded images in flash
 memory

---
 eink.hpp | 50 +++++++++++++++++++++++---------------------------
 1 file changed, 23 insertions(+), 27 deletions(-)

diff --git a/eink.hpp b/eink.hpp
index ce5f3e3..111de6f 100644
--- a/eink.hpp
+++ b/eink.hpp
@@ -1,7 +1,9 @@
 #pragma once
 
-#include <utility>
+#include <tuple>
+#include <type_traits>
 
+#include <cstddef>
 #include <cstdint>
 
 #include <avr/pgmspace.h>
@@ -146,41 +148,35 @@ class Eink {
 		_delay_ms(200);
 	}
 
-	template <typename Image>
-	static void draw(const Image &image)
+	template <typename RleImage>
+	static void draw(const RleImage &rleImage)
 	{
-		constexpr auto lookup = [](std::uint8_t bits) {
-			auto block = ImageBlock{};
-			util::for_constexpr(
-			    [&](const auto idx) {
-				    block[idx.value] = static_cast<Color>(bits % 3);
-				    bits /= 3;
-			    },
-			    std::make_index_sequence<BLOCK_SIZE>{});
-			return block;
+		constexpr auto pgm_load = [](const auto &object) {
+			using object_t = std::remove_cvref_t<decltype(object)>;
+			auto buffer = object_t{};
+			auto rawBuffer = reinterpret_cast<std::byte *>(&buffer);
+			for (auto i = std::size_t{0}; i < sizeof(object_t); ++i) {
+				rawBuffer[i] = static_cast<std::byte>(pgm_read_byte(&reinterpret_cast<const std::byte *>(&object)[i]));
+			}
+			return buffer;
 		};
 
-		constexpr auto sendImageChannel = [lookup](const auto command, const auto image) {
+		constexpr auto sendImageChannel = [pgm_load](const auto command, const auto &image) {
 			sendCommand(command);
-			auto buffer = std::uint8_t{0};
-			auto bufferPos = std::uint8_t{0};
-			for (auto i = std::uint16_t{0}; i < Width * Height / BLOCK_SIZE; i++) {
-				const auto block = lookup(pgm_read_byte(&image[i]));
-				for (auto p = std::uint8_t{0}; p < BLOCK_SIZE; ++p) {
-					const auto pixel = std::uint8_t{(command == Cmd::WRITE_RAM_BLACK) ? (block[p] != Color::BLACK)
-					                                                                  : (block[p] == Color::RED)};
-					buffer |= pixel << (7 - bufferPos++);
-					if (bufferPos == 8) {
-						sendData(buffer);
-						buffer = 0;
-						bufferPos = 0;
+			for (auto j = std::size_t{0}; j < image.size(); ++j) {
+				const auto [count, data] = pgm_load(image[j]);
+				for (auto i = std::uint16_t{0}; i < count; ++i) {
+					if (command == Cmd::WRITE_RAM_BLACK) {
+						sendData(data);
+					} else {
+						sendData(~data);
 					}
 				}
 			}
 		};
 
-		sendImageChannel(Cmd::WRITE_RAM_BLACK, image.data());
-		sendImageChannel(Cmd::WRITE_RAM_RED, image.data());
+		sendImageChannel(Cmd::WRITE_RAM_BLACK, std::get<0>(rleImage));
+		sendImageChannel(Cmd::WRITE_RAM_RED, std::get<1>(rleImage));
 
 		sendCommand(Cmd::DISPLAY_UPDATE_CONTROL_2);
 		sendData(0xF7);