KeplerNet

FitsFile.cs

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text;
using System.Drawing;
using SixLabors.ImageSharp;
using SixLabors.ImageSharp.Processing;
using SixLabors.ImageSharp.PixelFormats;

public class FitsFile : IDisposable
{
    const string END_FLAG = " END ";
    const int CHUNK_SIZE = 80;
    const int BLOCK_SIZE = 2880;

    Stream stream = null;
    public FitsFile(string path)
    {
        this.stream = new FileStream(path, FileMode.Open);
    }

    public void Reset()
    {
        this.stream.Position = 0;
    }

    public IEnumerable<KeyValuePair<string,string>> ReadHeader()
    {
        var headerString = "";
        var block = new byte[BLOCK_SIZE];
        while (true)
        {
            var amountRead = this.stream.Read(block,0 , BLOCK_SIZE);
            if (amountRead == 0) yield break;

            headerString += Encoding.UTF8.GetString(block);
            if (headerString.Contains(END_FLAG)){
                break;
            } 
        }            

        var position = 0;
        while (position < headerString.Length)
        {
            var line = string.Concat(headerString.Skip(position).Take(CHUNK_SIZE));
            position += CHUNK_SIZE;
            if (string.IsNullOrWhiteSpace(line)) continue;
            var kv = line.Split('=');
            if (kv.Length != 2)
            {
                yield return KeyValuePair.Create<string,string>("TEXT", line);
                if (line.Trim() == "END")
                {
                    yield break;
                }
                continue;
            } 
            yield return KeyValuePair.Create<string,string>(kv[0].Trim(), kv[1].Trim());
        }
    }

    const int WIDTH = 1132;
    const int HEIGHT = 1070;


    public Image<Rgba32> ReadImage()
    {
        var position = this.stream.Position;

        // hard code the min/max 32 bit pixel values we can expect from the image.
        var max = (double)(Int32.MaxValue * 0.5625);
        var min = (double)(Int32.MaxValue * 0.52734375);
        
        this.stream.Position = position;

        var image = new Image<Rgba32>(WIDTH, HEIGHT);
        var buffer = new byte[4];
        for  (var y = 0; y < HEIGHT; y++)
        {
            for (var x = 0; x < WIDTH; x++)
            {
                stream.Read(buffer, 0, buffer.Length);
                var value = (double)BitConverter.ToInt32(buffer.Reverse().ToArray());
                byte output = (byte)Math.Min(255,( (256.0 * Math.Max(0,value - min)) / (max - min) ));
   
                var colour = new Rgba32(output, output, output, 255);
                image[x,y] = colour;
            }
        }
        
        // round off to the next block
        stream.Position += (WIDTH * HEIGHT * 4) % BLOCK_SIZE;
        return image;
    }

    public void Dispose()
    {
        this.stream.Close();
    }
}

KeplerNet.csproj

<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <OutputType>Exe</OutputType>
    <TargetFramework>netcoreapp2.1</TargetFramework>
  </PropertyGroup>

  <ItemGroup>
    <PackageReference Include="SixLabors.ImageSharp" Version="1.0.0-beta0005" />
    <PackageReference Include="SixLabors.ImageSharp.Drawing" Version="1.0.0-beta0005" />
  </ItemGroup>

</Project>

Program.cs

using System;
using System.IO;
using System.Linq;
using SixLabors.ImageSharp.Formats.Bmp;

namespace KeplerNet
{
    class Program
    {
        static void Main(string[] args)
        {
            var path = @"C:\Users\richard.astbury\code\kep\ktwo2014070234206-c00_ffi-cal.fits";

            using (var ffi = new FitsFile(path))
            {
                //Console.WriteLine("HEADER");
                foreach (var header in ffi.ReadHeader())
                {
                   // Console.WriteLine($"{header.Key} = {header.Value}");
                }

                // only extract the first image
                for (var i = 0; i < 1; i++) 
                {
                    //Console.WriteLine($"FILE {i}");
                    foreach (var header in ffi.ReadHeader())
                    {
                        //Console.WriteLine($"{header.Key} = {header.Value}");
                    }
                    using (var image = ffi.ReadImage())
                    using (var fs = new FileStream($"output{i}.bmp", FileMode.CreateNew))
                    {
                        image.Save(fs, new BmpEncoder());
                    }
                }

            }
        }
    }
}