Support reading PBM images & fix all Netpbm readers

libs/gfx/include/psemek/gfx/pixmap.hpp

@@ -58,6 +58,7 @@ namespace psemek::gfx
 	using pixmap_rgba = basic_pixmap<color_rgba>;
 	using pixmap_float = basic_pixmap<float>;
 
+	pixmap_monochrome read_pbm(std::istream & is);
 	pixmap_monochrome read_pgm(std::istream & is);
 	pixmap_rgb read_ppm(std::istream & is);
 

libs/gfx/source/pixmap.cpp

@@ -1,10 +1,70 @@
 #include <psemek/gfx/pixmap.hpp>
 
 #include <iostream>
+#include <sstream>
+#include <vector>
 
 namespace psemek::gfx
 {
 
+	pixmap_monochrome read_pbm(std::istream & is)
+	{
+		auto fail = [](std::string str)
+		{
+			throw std::runtime_error("Error loading PBM image: " + str);
+		};
+
+		std::string line;
+		std::getline(is, line);
+
+		bool binary = true;
+
+		if (line == "P1")
+		{
+			binary = false;
+		}
+		else if (line == "P4")
+		{
+			binary = true;
+		}
+		else
+			fail("unknown format " + line);
+
+		if (!binary)
+			fail("P1 format is not supported");
+
+		std::getline(is, line);
+		std::istringstream sline(line);
+
+		std::size_t width, height;
+		pixmap_monochrome pixmap;
+
+		sline >> width >> height;
+
+		pixmap.resize(width, height);
+
+		std::size_t bytes = width * height;
+		if ((bytes % 8) == 0)
+			bytes = bytes / 8;
+		else
+			bytes = (bytes + 7) / 8;
+		std::vector<std::uint8_t> data(bytes);
+		is.read(reinterpret_cast<char *>(data.data()), bytes);
+
+		for (std::size_t i = 0; i < width * height; ++i)
+		{
+			std::size_t b = i / 8;
+			std::size_t o = 7 - (i % 8);
+			bool const white = (data[b] & (1 << o)) == 0;
+			pixmap.data()[i] = white ? 255 : 0;
+		}
+
+		if (!is)
+			fail("stream error");
+
+		return pixmap;
+	}
+
 	pixmap_monochrome read_pgm(std::istream & is)
 	{
 		auto fail = [](std::string str)
@@ -28,11 +88,18 @@ namespace psemek::gfx
 		else
 			fail("unknown format " + line);
 
+		std::getline(is, line);
+		std::istringstream sline(line);
+
 		std::size_t width, height;
 		std::size_t max;
 		pixmap_monochrome pixmap;
 
-		is >> width >> height >> max;
+		sline >> width >> height;
+
+		std::getline(is, line);
+		sline.str(line);
+		sline >> max;
 
 		if (max != 255)
 			fail("max value " + std::to_string(max) + " is not supported");
@@ -73,11 +140,18 @@ namespace psemek::gfx
 		else
 			fail("unknown format " + line);
 
+		std::getline(is, line);
+		std::istringstream sline(line);
+
 		std::size_t width, height;
 		std::size_t max;
 		pixmap_rgb pixmap;
 
-		is >> width >> height >> max;
+		sline >> width >> height;
+
+		std::getline(is, line);
+		sline.str(line);
+		sline >> max;
 
 		if (max != 255)
 			fail("max value " + std::to_string(max) + " is not supported");