boston 03.11visualization workshop the esa/eso/nasa photoshop fits liberator v.2 and its metadata...

Boston 03.11 Visualization workshop

The ESA/ESO/NASA Photoshop FITS Liberator v.2 and its metadata tools

Lars Lindberg Christensen (ESA/Hubble)Robert Hurt (NASA/SSC)

Boston 03.11 Visualization workshop

Contents

• Intro– Background– What does it do?– What is it good for?

• Workflow

• More about scaling and stretch– Dynamic range– Stretch functions– Scaling

• Advanced workflow• Metadata• Virtual Repository• The future of the Liberator

This talk will discuss the recent advances of the "FITS Liberator" tool and will explain the change in workflow philosophy. We will demonstrate the way it can be used to add metadata to the images and discuss why this should be done. Metadata tagging is the first, and perhaps most important, step towards making our images more globally accessible. We will also touch on the progress of our work with the "Virtual Repository" concept.

Boston 03.11 Visualization workshop

Acknowledgements

The team that produced the ESA/ESO/NASA Photoshop FITS Liberator consists of:

• Project Leader: Lars Lindberg Christensen (lars@eso.org)• Development Leader: Lars Holm Nielsen• Core functionality: Kasper K. Nielsen• Engine and GUI: Teis Johansen• Scientific support: Robert Hurt• Technical support and testing: Zolt Levay, Bob Fosbury and Richard

Hook.

The ESA/ESO/NASA Photoshop FITS Liberator uses NASA’s CFITSIO library.

FITS is an abbreviation for Flexible Image Transport System, has been a standard for astronomical images since 1982 and is recognized by the International Astronomical Union.

Boston 03.11 Visualization workshop

Background

• The ESA/ESO/NASA Photoshop FITS Liberator has, since it was released in July 2004, given a worldwide audience of 50,000 easy access to astronomical FITS images.

• The Liberator has in this way become the ‘industry standard’ for the production of ‘pretty pictures’.

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The ‘problem’ and the ‘solution’

Problem• Monochrome, noisy raw FITS data -> clean colour images that represent

the Universe:Maximize tonal range, avoid losing resolution, stay honest to data.

• Surplus of dynamic range in data. Limited dynamic range in output.• Need for speed.• The FITS format is very versatile, and therefore more difficult to ‘handle’

than e.g. a tiff file.• Science software (IRAF, Midas etc.) limited, slow and inaccessible.

Solution• Photoshop + FITS plug-in.

The plug-in is free and can be downloaded from: http://www.spacetelescope.org/projects/fits_liberator

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What does it do?

• Fully-functional interactive FITS reader• Mac/PC• Adobe Photoshop CS2/CS, 7.0, Elements 2+• A simple Intuitive interactive graphical user interface allows:

– Quickly assessment of the data– Easy adjustment of black and white levels– Scaling– Fast application of multiple stretch function (Log, Sqrt, ASinH

etc.)– Full overview of image statistics– Dynamically updated histogram– FITS images with up to 4 billion greyscales (32 bit)– FITS images with up to 500+ million pixels

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What is it good for?

• For combining greyscale images to colour images• For quick previews of data• Browse FITS header• For educational projects about digital images• Add metadata to the data• And more …

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Workflow

1. Open input image from the astronomical processing (reduced, cleaned).

2. Set White and Black levels to give a nice contrast without too much black and too saturated areas.

3. Scale the image to prepare for the Stretch function.4. Apply a Stretch function to enhance fainter parts and suppress

brighter parts of the image.5. Click ok to import the image into Photoshop.6. Combine multiple exposures, improve colour balance, crop,

clean.7. Add metadata8. Publish

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Hands-on demo

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Dynamic range

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Striking a balance

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Different stretches

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Stretch functions

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Stretch functions – Logarithmic plot

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Image scaling and stretches

• Data scaling can be significant– The range of pixel values

• Sqrt(x), CubeRoot(x)– “self-similar” functions: Data scaling has no effect

• Log(1+x), ASinH(x)– Strongly dependant on scale– Calibration can change appearance dramatically– Choice of scaling gives flexible dynamic range handling

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Log(1+x) with different scaling

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ASinH(x) with different scaling

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Mismatched stretch functions

ASinH red, Sqrt green Sqrt red + green

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Hands-on

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Virtual repository IAU Programme Group

• The volume of astronomical data is exploding (VOs)• In VO EPO we ultimately would like to give access to real data in a “Digital

Universe”, but this is a major undertaking• Complex datasets• Raw data are ‘dirty’• Laypeople and teachers lack the background to understand many of the issues• Meanwhile, the volume of digital products (outreach images and videos) is all the

time increasing• As a first step how do we better share resources internally?• Ultimately, how do we allow the public better access to images, videos and other

materials?• Astro-Google?=>• The purpose of the group is: “To construct the framework for a virtual repository to

allow outreach resources across projects and country borders to be ‘catalogued’ in a virtual repository and accessed by educators, press, students and public through specialized visual tools combined with search engines.”

http://www.communicatingastronomy.org/repository/virtual_repository.html

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Virtual!

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Components

1) Metadata travelling with the data2) A centralized organizer / controller3) A list (database) containing the data4) A protocol

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Status

Concept: The concept of the Virtual Repository has been thought out, discussed and improved to a degree where real implementation can start.

FITS Liberator now has metadata support. International collaboration: Ties have been made with the group at

STScI/Virtual Cosmos, led by Frank Summers, working on metadata tagging the outreach images from the Hubble Space Telescope and making them widely accessible.

Implementation: A student from the University of Copenhagen, Kasper Nielsen, will in the Autumn 2005 start working on the practical issues of how the Virtual Repository could be realised. The project will give an overview and description of the Virtual Repository solution and its components, as well as how some of these are actually implemented. The project is expected to finish in January 2006.

Funding: A proposal for the EC call for proposal for the part of the e-Content Plus programme is currently under preparation. This involves all US/European interested parties. The total budget is 3.5 MEUR with a partial funding part from the EC of the order of 2 MEUR. The proposal has the goal to give “European-wide access to the treasure trove of celestial images from anywhere, anytime, moving the astronomical images into the 21st Century“. The duration of the project is 30 months starting in 2006.

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Metadata

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Metadata 2

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Proposed workflow for new images

1. Open the exposure in Liberator. 2. “Do the image stuff”3. The Liberator transfers what FITS keywords we have defined (if present). 4. The Liberator has some standard fields retained from last time it was used.5. The used fills out some remaining fields.6. User clicks OK.7. The Liberator fills out the image processing fields.8. The same procedure is repeated for 2 or more other exposures9. With the FITS Composer tool:

1. Three (or more) exposures are merged into a layered file with the right adjustment layers

2. The three (or more) sets of metadata are concatenated. 10. The user finishes the image and perhaps adds comments to the CreationNotes and fills in the

Coverage.Spectral.ImageColormap.11. The user saves the image as a tiff file.12. The user opens the STScI WCS Mapping Tool together with the one of the original FITS files

that has the highest S/N.13. The user clicks to connect the same stars in the two images.14. The tool overwrites the coordinate (WCS) keywords in the XMP data15. The tiff file is saved again.

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The future of the Liberator

• Metadata tags specification to be approved by IVOA, IAU?• Version 2.1

– FITS Composer 1.0– WFPC2 Mosaicator 1.0– Minor bugfixes

• Version 3.0– Splitting of GUI into advanced and simple panes– Equation editor– Batch processing– Undo operations– Open source?– Preferences settings– Your ideas…

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Web site

http://www.spacetelescope.org/projects/fits_liberator