From f688471fa4900855af71efd5621ded62e27b116d Mon Sep 17 00:00:00 2001
From: GeorgH93 <git@georgh93.eu>
Date: Tue, 15 Dec 2020 22:54:26 +0100
Subject: [PATCH] Add basic pnm support

---
 openVulkanoCpp/IO/Files/Pnm.hpp | 121 ++++++++++++++++++++++++++++++++
 1 file changed, 121 insertions(+)
 create mode 100644 openVulkanoCpp/IO/Files/Pnm.hpp

diff --git a/openVulkanoCpp/IO/Files/Pnm.hpp b/openVulkanoCpp/IO/Files/Pnm.hpp
new file mode 100644
index 0000000..bd8a606
--- /dev/null
+++ b/openVulkanoCpp/IO/Files/Pnm.hpp
@@ -0,0 +1,121 @@
+/*
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+#pragma once
+
+#include <inttypes.h>
+#include <string>
+#include <sstream>
+#include <memory>
+#include <cmath>
+
+namespace openVulkanoCpp
+{
+	//TODO handle comments
+	/**
+	 * Implements Portable Anymap file headers
+	 * See https://de.wikipedia.org/wiki/Portable_Anymap
+	 */
+	class PnmHeader
+	{
+		static constexpr std::string_view FILE_TYPES[] = { "PBM", "PGM", "PPM" };
+		static constexpr std::string_view FILE_EXT[] = { ".pbm", ".pgm", ".ppm" };
+	public:
+		enum class ColorMode : uint8_t { BW = 1, GRAY, COLOR };
+
+		uint32_t width, height, maxValue;
+		ColorMode color;
+		bool ascii;
+
+		constexpr PnmHeader() : width(0), height(0), maxValue(0), color(ColorMode::GRAY), ascii(false) {}
+
+		constexpr PnmHeader(uint32_t width, uint32_t height, bool color, uint32_t maxValue = 255, bool ascii = false) :
+				width(width), height(height), maxValue(maxValue), color(color ? ColorMode::COLOR : ColorMode::GRAY), ascii(ascii)
+		{}
+
+		constexpr PnmHeader(uint32_t width, uint32_t height, ColorMode color = ColorMode::COLOR, uint32_t maxValue = 255, bool ascii = false) :
+				width(width), height(height), maxValue(maxValue), color(color), ascii(ascii)
+		{}
+
+		constexpr std::string_view GetFileType() const
+		{
+			return FILE_TYPES[static_cast<uint8_t>(color) - 1];
+		}
+
+		constexpr std::string_view GetFileExtension() const
+		{
+			return FILE_EXT[static_cast<uint8_t>(color) - 1];
+		}
+
+		std::string ToString() const
+		{
+			std::stringstream headerStream;
+			headerStream << *this;
+			return headerStream.str();
+		}
+
+		constexpr uint8_t GetMagicNumberValue() const
+		{
+			uint8_t value = static_cast<uint8_t>(color);
+			if (!ascii) value += 3;
+			return value;
+		}
+
+		friend std::ostream& operator<< (std::ostream& outStream, const PnmHeader& pnmHeader)
+		{
+			outStream << 'P';
+			outStream << ('0' + pnmHeader.GetMagicNumberValue());
+			outStream << '\n';
+			outStream << pnmHeader.width << ' ' << pnmHeader.height << '\n';
+			outStream << pnmHeader.maxValue << '\n';
+			return outStream;
+		}
+
+		friend std::istream& operator>> (std::istream& inStream, PnmHeader& pnmHeader)
+		{
+			std::string marker;
+			inStream >> marker;
+			if (marker.length() != 2 || marker[0] != 'P') throw std::runtime_error("Malformed PNM header!");
+			uint8_t val = marker[1] - '0';
+			if (val > 6) throw std::runtime_error("Malformed PNM header!");
+			pnmHeader.ascii = val < 4;
+			pnmHeader.color = static_cast<ColorMode>(val & 0x11);
+			inStream >> pnmHeader.width >> pnmHeader.height;
+			inStream >> pnmHeader.maxValue;
+			return inStream;
+		}
+
+		constexpr size_t GetImageSize() const
+		{
+			size_t size = height * width;
+			if (color == ColorMode::COLOR)
+			{
+				size *= 3;
+				if (maxValue > 255) size *= 2;
+				return size;
+			}
+			if (color == ColorMode::BW)
+			{
+				return std::ceil(size / 8.0);
+			}
+			return size;
+		}
+
+		static std::pair<PnmHeader, std::unique_ptr<char[]>> ReadImage(std::istream& inStream)
+		{
+			std::pair<PnmHeader, std::unique_ptr<char[]>> image;
+			inStream >> image.first;
+
+			// TODO handle ascii mode
+			if (image.first.ascii) throw std::runtime_error("ascii mode not supported!");
+
+			size_t size = image.first.GetImageSize();
+			image.second = std::make_unique<char[]>(size);
+			inStream.read(image.second.get(), size);
+			return image;
+		};
+	};
+}