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Topic: Hi-res images download

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jediknight (Over 1 year ago)
Hi,

I'd like to download and save locally the high resolution images making up a synth. I can't find their url though. In the json string describing the synth the image_map element contains a list of image elements each of which specifies the image dimensions in pixel and its url. These images seem to be lower res with respect to those shown during the navigation of the synth, and their name is "thumb.jpg". So, does someone know where the hi res ones are located?

Many thanks in advance
Nathanael (Over 1 year ago)
jediknight, 

Before photos are uploaded to the photosynth servers they are converted to the Deep Zoom Image format - a multi-resolution image pyramid which uses the original resolution as the base and each subsequent layer is half the width and half the height as the previous layer until the tip of the pyramid is a single pixel.

Each of these resolutions is also divided into tiles - usually 256 x 256 pixels, but not always. 

An important note for someone planning to piece the tiles that comprise the original resolution back together is the number of pixels that each tile overlaps its neighbours. (This pixel overlap is needed for purposes of blending when loading new tiles in without showing seams between the tiles as you blur and fade new layers in.)
jediknight (Over 1 year ago)
Thanks for your answer Nathanael,

I will learn more about this Deep Zoom Image format then.
Is the overlap amount dependent on this format, or the synther decides it arbitrarily? In such a situation, is this information described somewhere?

Thank you
Nathanael (Over 1 year ago)
You can gain a deeper understanding of what this looks like practically by: 

1a: Opening the following directory when you are creating a new photosynth: %temp%\photosynther\images
1b: Copy any of the .dziz files out of this folder and extract them as you would any .zip file (this is precisely what they are - deep zoom image zip)
1c: This will also make clear where the thumb.jpg sits in relation to the image pyramid. Henri Astre reports ( http://bit.ly/photosynththumbsexif ) that the entire metadata of the original image is stored within the thumb.jpg files whereas the tiles are devoid of metadata (obviously, it would be inefficient to redundantly store it in each of the tiles).

or alternately by 

2a: Downloading Deep Zoom Composer
2b: Creating a new project with at least one decently high resolution image
2c: Exporting for Seadragon AJAX to a folder on your hard drive
2d: Exploring this folder for the DZI
Nathanael (Over 1 year ago)
Useful links for more information: 
The Photosynth Web Service: http://photosynth.net/photosynthws/PhotosynthService.asmx (I suppose you are already using this to query for files relating to a particular synth?)

Seadragon Developer: Format Overview: http://seadragon.com/developer/creating-content/overview/
Seadragon Developer: Conversion Tools: http://seadragon.com/developer/creating-content/ (Many open source options)
Public MSDN documentation: http://bit.ly/dziformat
Blog posts about Deep Zoom Collections: http://bit.ly/dzcblog1 http://bit.ly/dzcblog2

Open source DZI viewers: (to help you see how the image pyramid is parsed)
Seadragon AJAX: http://bit.ly/seadragonajax
OpenZoom: http://openzoom.org/


Finally, you should go see Henri Astre's PhotoSynthTileDownloader. 
http://youtu.be/xqeV3pI1TfU?hd=1
http://www.visual-experiments.com/2010/09/08/introducing-opensynther/
Nathanael (Over 1 year ago)
@jediknight, the tile overlap should be specified in the XML of the DZI or the DZC, I believe.
Nathanael (Over 1 year ago)
@jediknight, to be clear, the tile overlap I am describing is how much tiles of the same image overlap each other, not anything to do with how much one photo overlaps with another.

Also, the tile size, image resolution, etc. should also be found in the DZI and DZC's XML.

For some links to some videos about Seadragon|Deep Zoom, please scroll to the end of this link: 
http://photosynth.net/discussion.aspx?cat=ceca0f30-0f7c-4468-811a-32b623ea8563&dis=ab1ce97d-6518-4dc1-bbb6-0b9a8b1257ac
Nathanael (Over 1 year ago)
Also, here's a discussion between some devs who wanted more detail than was provided on Seadragon.com and Aseem Kishore and Daniel Gasienica of the Seadragon team. Some questions you may have are answered in the discussion and a helpful entry in Daniel's web log is referenced.
http://getsatisfaction.com/livelabs/topics/dzi_format_not_included_on_seadragon_com

Also, this discussion features Aseem going into detail about tile size where he links to the DZI index for this image: http://seadragon.com/view/1
http://getsatisfaction.com/livelabs/topics/right_and_lower_border_tiles_distorted#reply_3346252
jediknight (Over 1 year ago)
Nathanael,

thank you so much for your helpfulness, I'll examine the material you pointed out.
To answer your question, yes, I'm querying the webservice using GetCollectionData and then use  to get json data describing the synth.
Seems that the json format is undocumented though, so it's very hard to understand what those elements represent (as I wrote in another post I'm interested in those relative to the cameras).

Best regards
Nathanael (Over 1 year ago)
For cross referential purposes, JediKnight also started a corresponding topic on the old forum which can also be checked for answers: 
http://getsatisfaction.com/livelabs/topics/synth_high_resolution_images_location
Nathaniel -- thanks very much for pulling all this information together. You're a (no, I mean *the*) star ofthe Photosynth community.
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