# FITS Liberator

The ESA/ESO/NASA FITS (Flexible Image Transport System) Liberator is a free software program for processing and editing astronomical data in the FITS format to reproduce images of the universe. Version 3 and later are standalone programs; earlier versions were plugins for Adobe Photoshop. FITS Liberator is free software released under the BSD-3 license. The engine behind the FITS Liberator is NASA's CFITSIO library.
Although the first version of the software was a tool used mainly by professional astronomers, efforts have been made to bring the tool to the homes of educators and students. The FITS Liberator has become the industry standard for professional imaging scientists at the European Space Agency (ESA), the European Southern Observatory (ESO), and the U.S. National Aeronautics and Space Administration (NASA). It uses images from the Hubble Space Telescope (HST) and the Very Large Telescope (VLT), among others, to craft astronomical images.
The first and second versions of the FITS Liberator were released in July 2004 and August 2005 respectively, the version, v3.0.1, was released in February 2012.

## Versions
### Version 1

Version 1 of the ESA/ESO/NASA Photoshop FITS Liberator was completed in July 2004 by imaging scientists at the European Space Agency (ESA), the European Southern Observatory (ESO), and the National Aeronautics and Space Administration (NASA). Version 1 allowed all types of FITS images to be opened and also some limited interaction with the images.

### Version 2

The basic workflow is to open a FITS image, study it in the Preview window, adjust the black-and-white levels (6) to give a reasonable contrast and then set the input range for the scaling of the image by clicking the Auto Scaling Button (7). Test different values of the Scaled Peak level to scale the image to better fit with one of the possible Stretch functions (8).
Version 2 of the ESA/ESO/NASA Photoshop FITS Liberator image processing software made it easier and faster to create colour images from raw observations. Updates included:
* FITS images with up to 4 billion grey scales can be processed (32 bit support).
* FITS images with up to 500 million pixels or more can be processed (100 times larger than standard images from a digital camera).
* Re-designed workflow and user interface. The plug-in remembers previous settings.
* New options for advanced scaling and stretching.
A section of v2.0 was dedicated to metadata input and the user also was given access to a text version of the original FITS header.
An updated version of the software containing new scaling and stretching tools allows more manipulation of astronomical images. An update in v2.1 allows users to embed descriptive information about the image and what it shows within the final image. Based on a new standard for Astronomy Visualization Metadata (AVM), this information is stored in the standard manner comparable to that used by digital cameras to record exposure information.
The ESA/ESO/NASA WFPC2 Mosaicator: This add-on tool works on Hubble WFPC2 images. It generates a WFPC2 mosaic file from one WFPC2 file containing four CCD images in individual planes.
The ESA/ESO/NASA FITS Concatenator: This Adobe Photoshop script combines the metadata from two or more individual exposures after the FITS Liberation process.

### Version 3

Version 3.0 of the FITS Liberator included the following new features:
* FITS Liberator became a stand-alone application, no longer requiring Adobe Photoshop.
* Processing medium-sized images became up to 35% faster due to improved memory management.
* Processing large images became faster, due to delayed application of stretch functions.
* FITS Liberator now saves TIFF files that opened in most image processing software.

### Version 4

Version 4.0 of the FITS Liberator was released on 4 March 2021, and includes new features:
* 64 bit operating systems are supported.
* Mac OS X, Windows, and Linux support.
* Command Line Interface for batch processing of FITS files.
* Full support for big images (even greater than available memory).
* Dark mode.
* Full screen mode.

## Usage

For experienced users, there is a Quick Start Guide available at the FITS Liberator website.
For new users, a Full User Guide for the FITS Liberator 3, can be obtained from the European homepage of the NASA/ESA Hubble Space Telescope.