convert_tojpg.cs

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Net.Http;
using System.Text;
using System.Threading.Tasks;
using Xamarin.Forms;

namespace MriFilesConvert
{
	public partial class MainPage : ContentPage
	{
        byte[] imageContent;
        public MainPage()
		{
			InitializeComponent();
		}

        protected async override void OnAppearing()
        {
            base.OnAppearing();
            imageContent = await GetMriFilesContent("https://f01.mrcdn.info/file/mrfiles/h/3/q/f/vS.kXnoNLt-.mri");
        }

        private async Task<byte[]> GetMriFilesContent(string url)
        {
            HttpClient _client = new HttpClient();
            var content = await _client.GetAsync(url);

            var page_response = await content.Content.ReadAsByteArrayAsync();
            await DisplayAlert("Page Replied", page_response.ToString(), "ok");
            string temp_data = await ConvertMriFilesToImages(page_response);
            return page_response;
        }

        private async Task<string> ConvertMriFilesToImages(byte[] fileContent)
        {
            int dataLength = fileContent.Length + 7;
            List<int> header = new List<int>() { };
            byte[] _header = new byte[15];
            _header[0] = 82;
            _header[1] = 73;
            _header[2] = 70;
            _header[3] = 70;
            _header[4] = Convert.ToByte(255 & dataLength);
            _header[5] = Convert.ToByte(dataLength >> 8 & 255);
            _header[6] = Convert.ToByte(dataLength >> 16 & 255);
            _header[7] = Convert.ToByte(dataLength >> 24 & 255);
            _header[8] = 87;
            _header[9] = 69;
            _header[10] = 66;
            _header[11] = 80;
            _header[12] = 86;
            _header[13] = 80;
            _header[14] = 56;
            byte[] newcontent = new byte[dataLength];
            int stepper = 0;
            await DisplayAlert("Header Value", string.Join(",", header), "ok");
            foreach (var item in fileContent)
            {
                newcontent[stepper] = Convert.ToByte(Convert.ToInt64(item) ^ 101);
                if (!(stepper>dataLength))
                    stepper++;
            }

            byte[] rv = new byte[_header.Length + newcontent.Length];
            System.Buffer.BlockCopy(_header, 0, rv, 0, _header.Length);
            System.Buffer.BlockCopy(newcontent, 0, rv, _header.Length, newcontent.Length);
            var temp = "";
            foreach (var item in rv)
            {
                temp += (char)item;
            }
            await DisplayAlert("New Content", newcontent.ToList()[0].ToString(), "ok");
            if (SaveFile(newcontent))
                await DisplayAlert("Done", "Success", "ok");
            else
                await DisplayAlert("Failed", "Failed", "ok");

            return "Hello";
        }

        public bool SaveFile(byte[] dataToWrite)
        {
            try
            {
                string fileName = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.MyPictures), "image.jpg");
                var temp = Convert.ToBase64String(dataToWrite);
                File.WriteAllBytes(fileName, dataToWrite);

                return true;
            }
            catch (Exception FileHandlingError)
            {
                Console.WriteLine("File Handling Error : " + FileHandlingError);
                //throw;
                return false;
            }
        }

    }
}