Read dimensions of BMP image

Create a program in C# to read the dimensions of an image in Windows bitmap format. You should first check that it is a valid .bmp image, reviewing the header data 'BM'. If it is a valid .bmp image then it obtained its dimensions (width x height) and display them on the screen.

It is a format of the Windows operating system. You can save images up to 24 bits (16.7 million colors).

The header of a BMP image is as follows:

Input

Output

48x48

Solution

using System;
using System.IO;

public class ReadDimensionsBmpImage
{
    public static void Main(string[] args)
    {
        string fileName = "logo.bmp";
        int size = 54, width, height;
        byte[] data = new byte[size];

        using (FileStream file = File.OpenRead(fileName))
        {
            file.Read(data, 0, size);
        }

        if (data[0] != 'B' || data[1] != 'M')
        {
            return; // Not a BMP file
        }

        width = data[18] + (data[19] * 256) +
               (data[20] * 256 * 256) +
               (data[21] * 256 * 256 * 256);

        height = data[22] + (data[23] * 256) +
                (data[24] * 256 * 256) +
                (data[25] * 256 * 256 * 256);

        Console.WriteLine("{0}x{1}", width, height);
    }
}