How to Divide an array on c#?

Question

I have to do a program that read and image and puts it into a byte array

var Imagenoriginal = File.ReadAllBytes("10M.bmp");

And Divide That byte Array into 3 Diferent Arrays in order to send each one of this new arrays to other computer ( Using Pipes ) to process them there and finally take them back to the origial computer and finally give the result. But my question Is how do I do an Algorithm able to divide the byte array in three different bytes arrays if the image selected can have diferent size. Thanks for your help, have a nice day. =)

Answer 1

You can divide length of array, so you have three integers n1 , n2 and n3 with all of them summing up to array.Length . Then, this snippet, using LINQ should be of help:

var arr1 = sourceArray.Take(n1).ToArray();
var arr2 = sourceArray.Skip(n1).Take(n2).ToArray();
var arr3 = sourceArray.Skip(n1+n2).Take(n3).ToArray();

Now, in arr1 , arr2 and arr3 you will have three parts of your source array. You need to use LINQ, so in the beginning of the code don't forget using System.Linq; .

Answer 2

You can try like this:

public static IEnumerable<IEnumerable<T>> DivideArray<T>(this T[] array, int size)
{
    for (var i = 0; i < (float)array.Length / size; i++)
    {
        yield return array.Skip(i * size).Take(size);
    }
}

The call like this:

var arr = new byte[] {1, 2, 3, 4, 5,6};
var dividedArray = arr.DivideArray(3);

Here is a LINQ approach:

public List<List<byte>> DivideArray(List<byte> arr)
{
    return arr
             .Select((x, i) => new { Index = i, Value = x })
             .GroupBy(x => x.Index / 100)
             .Select(x => x.Select(v => v.Value).ToList())
             .ToList();
}

Answer 3

Have you considered using Streams ? You could extend the Stream class to provide the desired behavior, as follows:

public static class Utilities
{
    public static IEnumerable<byte[]> ReadBytes(this Stream input, long bufferSize)
    {
        byte[] buffer = new byte[bufferSize];
        int read;

        while ((read = input.Read(buffer, 0, buffer.Length)) > 0)
        {
            using (MemoryStream tempStream = new MemoryStream())
            {
                tempStream.Write(buffer, 0, read);
                yield return tempStream.ToArray();
            }            
        }
    }

    public static IEnumerable<byte[]> ReadBlocks(this Stream input, int nblocks)
    {
        long bufferSize = (long)Math.Ceiling((double)input.Length / nblocks);
        return input.ReadBytes(bufferSize);
    }
}

• The ReadBytes extension method reads the input Stream and returns its data as a sequence of byte arrays, using the specified bufferSize .

• The ReadBlocks extension method calls ReadBytes with the appropriate buffer size, so that the number of elements in the sequence equals nblocks .

You could then use ReadBlocks to achieve what you want:

public class Program
{
    static void Main()
    {
        FileStream inputStream = File.Open(@"E:\10M.bmp", FileMode.Open);
        const int nblocks = 3;

        foreach (byte[] block in inputStream.ReadBlocks(nblocks))
        {
            Console.WriteLine("{0} bytes", block.Length);
        }
    }
}

Note how ReadBytes uses tempStream and read to write in memory the bytes read from the input stream before converting them into an array of bytes, it solves the problem with the leftover bytes mentioned in the comments.