added reader and writer for Netpbm P5 and P6 files

README.md

@@ -146,6 +146,14 @@ Interface for reading and writing [PCM](https://en.wikipedia.org/wiki/Pulse-code
 
 Read and write [WAV](https://en.wikipedia.org/wiki/WAV) files
 
+### [pel.hh](pel.hh)
+
+Interface for reading and writing [pixel](https://en.wikipedia.org/wiki/Pixel) data
+
+### [netpbm.hh](netpbm.hh)
+
+Read and write [Netpbm](https://en.wikipedia.org/wiki/Netpbm) files
+
 ### [spline.hh](spline.hh)
 
 * Algorithm for computing uniform and [natural cubic splines](https://en.wikipedia.org/wiki/Spline_(mathematics)#Algorithm_for_computing_natural_cubic_splines)

netpbm.hh

@@ -0,0 +1,180 @@
+/*
+Read and write Netpbm files
+
+Copyright 2020 Ahmet Inan <inan@aicodix.de>
+*/
+
+#pragma once
+
+#include <fstream>
+#include "pel.hh"
+
+namespace DSP {
+
+template <typename TYPE>
+class ReadPNM : public ReadPEL<TYPE>
+{
+	std::ifstream is;
+	int width_, height_, maxval_;
+	bool mono_;
+
+	TYPE linear(int val)
+	{
+		int K0 = std::nearbyint(0.03928 * maxval_);
+		TYPE phi(12.92 * maxval_), a(0.055 * maxval_), gamma(2.4);
+		return val <= K0 ? val / phi : std::pow((val + a) / (maxval_ + a), gamma);
+	}
+	static bool space(int c)
+	{
+		return c == ' ' || c == '\n' || c == '\t';
+	}
+	static bool newline(int c)
+	{
+		return c == '\n';
+	}
+	static bool digit(int c)
+	{
+		return c >= '0' && c <= '9';
+	}
+	static int value(int c)
+	{
+		return c - '0';
+	}
+public:
+	ReadPNM(const char *name) : is(name, std::ios::binary)
+	{
+		if (is.get() != 'P')
+			return;
+		int c = is.get();
+		if (!digit(c))
+			return;
+		int number = value(c);
+		if (number == 5)
+			mono_ = true;
+		else if (number == 6)
+			mono_ = false;
+		else
+			return;
+		c = is.get();
+		if (!space(c))
+			return;
+		int num[3];
+		for (int i = 0; i < 3; ++i) {
+			if (newline(c))
+				for (c = is.get(); c == '#'; c = is.get())
+					while (is.good() && !newline(is.get()));
+			while (space(c))
+				c = is.get();
+			for (num[i] = 0; digit(c); c = is.get())
+				num[i] = 10 * num[i] + value(c);
+		}
+		if (!space(c))
+			return;
+		width_ = num[0];
+		height_ = num[1];
+		maxval_ = num[2];
+	}
+	void read(TYPE *buf, int num, int stride = -1)
+	{
+		if (mono_) {
+			if (stride < 0)
+				stride = 1;
+			for (int i = 0; i < num; ++i) {
+				int G = is.get();
+				buf[stride*i] = linear(G);
+			}
+		} else {
+			if (stride < 0)
+				stride = 3;
+			for (int i = 0; i < num; ++i) {
+				int R = is.get();
+				int G = is.get();
+				int B = is.get();
+				buf[stride*i+0] = linear(R);
+				buf[stride*i+1] = linear(G);
+				buf[stride*i+2] = linear(B);
+			}
+		}
+	}
+	bool good()
+	{
+		return is.good();
+	}
+	bool mono()
+	{
+		return mono_;
+	}
+	int width()
+	{
+		return width_;
+	}
+	int height()
+	{
+		return height_;
+	}
+};
+
+template <typename TYPE>
+class WritePNM : public WritePEL<TYPE>
+{
+	std::ofstream os;
+	int width_, height_, maxval_;
+	bool mono_;
+
+	int srgb(TYPE val)
+	{
+		TYPE K0(0.03928), a(0.055), phi(12.92), gamma(2.4);
+		val = std::min(std::max(val, TYPE(0)), TYPE(1));
+		val = val <= K0 / phi ? val * phi : (1 + a) * std::pow(val, 1 / gamma) - a;
+		return std::nearbyint(maxval_ * val);
+	}
+public:
+	WritePNM(const char *name, int width, int height, bool mono = false, int maxval = 255) :
+		os(name, std::ios::binary | std::ios::trunc),
+		width_(width), height_(height), maxval_(maxval), mono_(mono)
+	{
+		int number = mono ? 5 : 6;
+		os << 'P' << number << ' ' << width << ' ' << height << ' ' << maxval << '\n';
+	}
+	void write(const TYPE *buf, int num, int stride = -1)
+	{
+		if (mono_) {
+			if (stride < 0)
+				stride = 1;
+			for (int i = 0; i < num; ++i) {
+				int G = srgb(buf[stride*i]);
+				os.put(G);
+			}
+		} else {
+			if (stride < 0)
+				stride = 3;
+			for (int i = 0; i < num; ++i) {
+				int R = srgb(buf[stride*i+0]);
+				int G = srgb(buf[stride*i+1]);
+				int B = srgb(buf[stride*i+2]);
+				os.put(R);
+				os.put(G);
+				os.put(B);
+			}
+		}
+	}
+	bool good()
+	{
+		return os.good();
+	}
+	bool mono()
+	{
+		return mono_;
+	}
+	int width()
+	{
+		return width_;
+	}
+	int height()
+	{
+		return height_;
+	}
+};
+
+}
+

pel.hh

@@ -0,0 +1,34 @@
+/*
+Interface for reading and writing pixel data
+
+Copyright 2020 Ahmet Inan <inan@aicodix.de>
+*/
+
+#pragma once
+
+namespace DSP {
+
+template <typename TYPE>
+struct WritePEL
+{
+	virtual void write(const TYPE *, int, int = -1) = 0;
+	virtual bool good() = 0;
+	virtual bool mono() = 0;
+	virtual int width() = 0;
+	virtual int height() = 0;
+	virtual ~WritePEL() = default;
+};
+
+template <typename TYPE>
+struct ReadPEL
+{
+	virtual void read(TYPE *, int, int = -1) = 0;
+	virtual bool good() = 0;
+	virtual bool mono() = 0;
+	virtual int width() = 0;
+	virtual int height() = 0;
+	virtual ~ReadPEL() = default;
+};
+
+}
+