OS-Labs/lab1/src/libppm.cpp

#include "libppm.h"
#include <iostream>
#include <fstream>

using namespace std;

uint8_t skip_blanks_comments_while_reading(ifstream *read_stream) //returns the byte at the first position after the skipping of the blank space
{
	uint8_t val;
	while(true)
	{
		val = read_stream->get();
		if(val == '#')
		{
			while(val != '\n')
			{
				val = read_stream->get();
			}
		}
		if(val == '\n' || val == ' ' || val == '\t')
		{
			continue;
		}
		else if(val != '#')
			return val;
	}
	return val;
}

struct image_t* read_ppm_file(char* path_to_input_file)
{
	//cout << "input image file = " << path_to_input_file << "\n";
	
	ifstream read_stream(path_to_input_file, ios::binary | ios::in);
	
	if(read_stream.is_open())
	{
		struct image_t* image = new struct image_t;
		
		uint8_t val = skip_blanks_comments_while_reading(&read_stream); // 'P'
		val = read_stream.get(); //'6'
		
		// width
		val = skip_blanks_comments_while_reading(&read_stream);		
		while(true)
		{
			if(val == ' ' || val == '\t' || val == '\n')
				break;
			image->width = image->width * 10 + (val - '0');
			val = read_stream.get();
		}
		//cout << "width = " << image->width << "\n";
		
		// height
		val = skip_blanks_comments_while_reading(&read_stream);		
		while(true)
		{
			if(val == ' ' || val == '\t' || val == '\n')
				break;
			image->height = image->height * 10 + (val - '0');
			val = read_stream.get();
		}
		//cout << "height = " << image->height << "\n";
		
		image->image_pixels = new uint8_t**[image->height];
		for(int i = 0; i < image->height; i++)
		{
			image->image_pixels[i] = new uint8_t*[image->width];
			for(int j = 0; j < image->width; j++)
				image->image_pixels[i][j] = new uint8_t[3];
		}
		
		// maxval
		val = skip_blanks_comments_while_reading(&read_stream);		
		while(true)
		{
			if(val == ' ' || val == '\t' || val == '\n')
				break;
			val = read_stream.get();
		}
		
		// get pixel values
		val = skip_blanks_comments_while_reading(&read_stream);		
		for(int i = 0; i < image->height; i++)
		{
			for(int j = 0; j < image->width; j++)
			{
				for(int k = 0; k < 3; k++)
				{
					image->image_pixels[i][j][k] = val;
					val = read_stream.get(); //assuming maxval of <=255
				}
			}
		}
		//read_stream.seekg(-1, ios_base::cur);
		//read_stream.read(((char*)image->image_pixels), image->height * image->width * 3); //assuming maxval of <=255
		
		read_stream.close();
		
		return image;
	}
	else
	{
		cerr << "failed to open file " << path_to_input_file << "\n\n";
		exit(1);
	}
}

void write_ppm_file(char * path_to_output_file, struct image_t* image)
{
	//cout << "output image file = " << path_to_output_file << "\n";
	
	ofstream write_stream(path_to_output_file, ios::binary | ios::out);
	
	if(write_stream.is_open())
	{
		write_stream.write("P6\n", 3);
		std::string width_string = std::to_string(image->width);
		//cout << "width = " << width_string << "\n";
		write_stream.write(width_string.c_str(), width_string.length());
		write_stream.write(" ", 1);
		std::string height_string = std::to_string(image->height);
		//cout << "height = " << height_string << "\n";
		write_stream.write(height_string.c_str(), height_string.length());
		write_stream.write("\n255\n", 5);
		for(int i = 0; i < image->height; i++)
		{
			for(int j = 0; j < image->width; j++)
			{
				for(int k = 0; k < 3; k++)
				{
					write_stream.put(image->image_pixels[i][j][k]); //assuming maxval of <=255
				}
			}
		}
		//write_stream.write(((char*)image->image_pixels), image->height * image->width * 3);
		write_stream.close();
	}
	else
	{
		cerr << "failed to open file " << path_to_output_file << "\n\n";
		exit(1);
	}
}