Visor PGM Ejercicio C# - Curso de Programación C# (C Sharp)

// Importing the System namespace to use its classes
using System; 

using System.IO; // Importing the IO namespace to handle file operations

class PgmViewer
{
    // The main method, where the program execution begins
    static void Main(string[] args)
    {
        // Check if a file name has been provided as a command-line argument
        if (args.Length < 1)
        {
            // Display an error message if no file name is provided
            Console.WriteLine("You must provide a PGM file as an argument.");
            return; // Exit the program if no file is provided
        }

        // Retrieve the file name from the command-line arguments
        string fileName = args[0];

        try
        {
            // Read the entire PGM file into a byte array
            byte[] pgmData = File.ReadAllBytes(fileName);

            // Check if the file begins with "P5" to ensure it's a binary PGM file
            if (pgmData[0] != 'P' || pgmData[1] != '5')
            {
                // Display an error message if the file is not in PGM binary format
                Console.WriteLine("The file is not a binary PGM (P5) file.");
                return; // Exit the program if the format is incorrect
            }

            // Set the offset to start reading the header after "P5"
            int offset = 2; // Skip the first two characters "P5"

            // Read the image width and height, skipping spaces or newlines
            while (pgmData[offset] == 10 || pgmData[offset] == 32) offset++; // Skip spaces and newlines

            int width = 0, height = 0; // Initialize width and height of the image
            while (pgmData[offset] >= 48 && pgmData[offset] <= 57) width = width * 10 + (pgmData[offset++] - 48); // Read width (digits)
            while (pgmData[offset] == 32) offset++; // Skip the space between width and height
            while (pgmData[offset] >= 48 && pgmData[offset] <= 57) height = height * 10 + (pgmData[offset++] - 48); // Read height (digits)

            // Skip spaces or newlines before reading the max pixel value
            while (pgmData[offset] == 10 || pgmData[offset] == 32) offset++; // Skip spaces and newlines

            int maxValue = 0; // Initialize the max intensity value (typically 255)
            while (pgmData[offset] >= 48 && pgmData[offset] <= 57) maxValue = maxValue * 10 + (pgmData[offset++] - 48); // Read the max value (digits)

            // The image data starts after the header, so we copy it to a separate array
            byte[] pixelData = new byte[width * height]; // Allocate space for the pixel data
            Array.Copy(pgmData, offset, pixelData, 0, pixelData.Length); // Copy the pixel data into the array

            // Now we process and display the pixel data in the console
            for (int i = 0; i < pixelData.Length; i++)
            {
                int intensity = pixelData[i]; // Get the intensity value for the current pixel

                // Determine the character to print based on the intensity value
                char displayChar = intensity > 200 ? ' ' :  // If intensity is greater than 200, print a space
                                   (intensity >= 150) ? '.' :  // If intensity is between 150 and 199, print a dot
                                   (intensity >= 100) ? '-' :  // If intensity is between 100 and 149, print a dash
                                   (intensity >= 50) ? '=' :   // If intensity is between 50 and 99, print an equals sign
                                   '#';                        // If intensity is between 0 and 49, print a hash sign

                // Print the character for the current pixel
                Console.Write(displayChar);

                // If we've reached the end of a row, print a new line
                if ((i + 1) % width == 0)
                {
                    Console.WriteLine(); // Move to the next line after each row of pixels
                }
            }
        }
        catch (Exception ex)
        {
            // Display an error message if an exception occurs during file processing
            Console.WriteLine($"Error processing the file: {ex.Message}");
        }
    }
}