FITSReader 1.4.1

<font size="8">FITSReader</font>

<font size="5">Library that parses FITS image files according to NASA's FITS standard version 4.0 and provides methods to extract metadata, raw data, and normalized byte arrays that can be used to display FITS data as images.</font>

FITS File Overview

A Flexible Image Transport System (FITS) file is the standard archival data format for astronomical data sets.

Each FITS file contains one or more Header Data Units (HDUs). An HDU contains metadata (aka a header) about the data contained within the HDU. Each HDU optionally contains an array of data values immediately following the metadata.

See the official NASA documentation for more in-depth details about the format.

Library Overview

FITSFile

Terms and Abbreviations

• FITS - Flexible Image Transport System.
• HDU - Header Data Unit - A FITS file contains one or more HDUs that include metadata and optional data values.
• Header - Contains metadata about the image such as size, datatype, exposure settings, etc. All HDUs must have a header.
• Data Unit - Optional array of data values for an HDU.
• Normalizer - Used to convert HDU values into byte arrays that can be used for imaging.

Main Components

• FITSFile parses a FITS file and provides references to all of the HDUs within the file.
• FITSHeader contains methods to read header metadata and retrieve values from its associated data unit.
• FITSData contains basic info about the data unit such as mean, standard deviation, and basic image metadata. FITSHeader returns an IFITSData object which does not 'know' what type of data it contains. If you need the actual values, you will need to cast the data to the appropriate FITSData<T> type. (See usage example)
• Normalizer Generates a byte array of normalized values for a given min and max value. See below for list of supported data types.

Usage

1. Get a reference to a FITS file. (Synchronous methods available as well)

   var fileName = "ibzda1020_drz.fits";
   var fitsFile = await FITSFile.ReadFileAsync(fileName);
   

2. Find an interesting HDU. In this example we are looking for the first HDU that uses single-precision float data.

   var header = fileFile.Headers.Find(header => header.DataType == FITSDataType.SingleFloat);
   

3. Get the HDU's data. the FITSData object is cast to handle float values because that matches the data type of the HDU.

   var data = (FITSData<float>)header.Data;
   

4. Create a normalizer for the parsed data values which can be used to linearly normalize the data to byte values.

   var normalizer = new FloatLinearNormalizer(data.Values);
   

5. Set the normalizer to the desired min and max values. For example if we set min to 0 and max to 100, the values 0, 50, and 100 will normalize to 0, 127, and 255 respectively.

   normalizer.Min = data.Mean - data.StdDev;
   normalizer.Max = data.Mean + data.StdDev;
   

6. Get the normalized bytes that can then be used to generate an image from the HDU.

   var normalized = normalizer.Normalize();
   

Install

Stable Version

Find the latest stable version at nuget.org

Preview Version

Follow the instructions here to connect to the FITSPreview nuget feed.

Source

Code

Source code can be found on Azure DevOps. The following instructions assume you are using Git.

1. git clone https://MikeWestbrook@dev.azure.com/MikeWestbrook/FITS/_git/FITS
2. Open the Reader C# project with Visual Studio 2022

Release

Supported Data Types

FITS data supports many data types from single bytes to IEEE double-precision floating points. FITSReader supports the following data types. All supported data types will eventually be supported.

• IEEE single-precision floating point
• Char or single byte data