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Check and Validate GIF Image File in C#

This program checks if a GIF image file is correctly formatted by inspecting the first few bytes of the file. It reads the first four bytes to confirm if they match the ASCII codes for 'G', 'I', 'F', and '8' (0x47, 0x49, 0x46, 0x38). If the file appears to be a valid GIF file, the program further checks the next byte to determine if the version is "87" or "89" based on whether the byte is 7 or 9. This simple validation method ensures that the file is a GIF image and helps identify its version.



Group

File Handling in C#

Objective

1. The program will ask the user for the name of the GIF file to check.
2. It will open the file and read the first four bytes.
3. If the bytes match the expected "GIF8" signature, the program will continue checking the version byte.
4. If the version byte is 7, the program will identify the GIF as version 87. If the byte is 9, it will identify the GIF as version 89.
5. If the first four bytes do not match the expected signature, the program will inform the user that the file is not a valid GIF.

Create a C# program to check if a GIF image file seems to be correct. It must see if the first four bytes are G, I, F, 8. In case it seems correct, it must also display the GIF version (87 or 89), checking if the following byte is a 7 or a 9.

Example C# Exercise

 Copy C# Code 
using System;
using System.IO;

class GifValidator
{
    // Method to validate if a file is a correct GIF image and determine its version
    public static void CheckGifFile(string filePath)
    {
        // Step 1: Check if the file exists
        if (!File.Exists(filePath))
        {
            Console.WriteLine("The file does not exist.");
            return;
        }

        // Step 2: Open the file and read the first few bytes
        using (FileStream fs = new FileStream(filePath, FileMode.Open, FileAccess.Read))
        {
            // Step 3: Create a byte array to hold the first 5 bytes
            byte[] bytes = new byte[5];

            // Step 4: Read the first 5 bytes from the file
            fs.Read(bytes, 0, 5);

            // Step 5: Check if the first four bytes match "GIF8"
            if (bytes[0] == 0x47 && bytes[1] == 0x49 && bytes[2] == 0x46 && bytes[3] == 0x38)
            {
                // Step 6: Check the next byte to determine the version
                if (bytes[4] == 0x37)
                {
                    Console.WriteLine("This is a valid GIF file (Version 87).");
                }
                else if (bytes[4] == 0x39)
                {
                    Console.WriteLine("This is a valid GIF file (Version 89).");
                }
                else
                {
                    Console.WriteLine("This is a valid GIF file, but the version could not be determined.");
                }
            }
            else
            {
                // Step 7: If the first four bytes don't match, it's not a valid GIF
                Console.WriteLine("This is not a valid GIF file.");
            }
        }
    }
}

class Program
{
    static void Main(string[] args)
    {
        // Step 1: Ask the user for the name of the GIF file to validate
        Console.WriteLine("Enter the path of the GIF file to check:");

        // Step 2: Get the file path from the user
        string filePath = Console.ReadLine();

        // Step 3: Validate the GIF file
        GifValidator.CheckGifFile(filePath);
    }
}

 Output

// If the user provides a valid GIF file path (valid.gif), and the file has the first four bytes as GIF8 and the next byte is 0x37 (for version 87), the output will be:
This is a valid GIF file (Version 87).

//If the file has the first four bytes as GIF8 and the next byte is 0x39 (for version 89), the output will be:
This is a valid GIF file (Version 89).

//If the file does not have the GIF8 signature, the output will be:
This is not a valid GIF file.

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