Biggest image I have ever created created

While browsing Wikipedia I found some code to generate nice fractals.

I have adapted the code to create really huge images.

The largest I have to date is computed at 512000 x 300000 pixels. The image is black and white, I use a binary fromat to save space (1 bit/pixel), that still makes the uncompressed file about 20 Gigabytes. Computation time on a Core2Duo 2 Ghz is about 4 days (with some pausing).

I then compute a multiresultion tiff of half size (because it looks better). The final image is about 256000 x 150000.

Here is a detail:

Code I have wrtitten uses OpenMP #pragma. I had the opportunity of trying this code in a new Intel machine that has a total of 16 threads (2 CPUs x 4 Cores x 2 Hyperthreads).  Using a single  parallelfor  instruction allowed me to gain a factor of 10 over single threaded code. Not too bad.  Of course dynamic threads ala Intel TBB would have allowed further gains, but at the expense of more code.

What is your largest image ?

The largest images I have on my machine, viewable by VLIV are 86400 x 43200 = 3.7 Gigapixels
(It's the NASA Blue Marble NG) and 96512 x 88832 = 8.6 Gigapixels.

What are the largest images you have been able to view with VLIV ?
Please post them in comments.

Printing size of very large images

Imagine we have a Very Large Image (such as the one generated from NASA Blue Marble NG).
The dimensions in pixels are 86400 x 43200 (remember it's the Earth at 500 m/pixel).

My screen (20 inches 16/10 DELL 2005 FPW) dimensions are about 44 cm x 27 cm (17 x 10.6 inches) for 1680 x 1050 pixels.
Simple math gives us 86400 / 1680 = 52 and 43200 / 1050 = 41.
This means that in order to view the complete image, we would need a matrix of 52 x 41 = 2132 monitors !!

Now lets' go to printing. Maximal resolution the eye can distinguish is about 254 DPI (100 pixels / cm). Now this means that the printed size of the image is : 86400 / 100 = 864 cm and
43200 / 100 = 432 cm (340 x 170 inches). This is huge, it would require more than 640 A4 sheets of paper !!


I have a poster printed from the NASA image. It's about 122 x 76 cm and has been printed at 254 DPI. While it's already very nice, it's only 1/8 of the possible printed size at full resolution.
Here is a small version :

Very Large Images on your disk

While there are quite many images you can view on the Web (see previous post), there are actually very few you can download to your machine.

You can find few on my VLIV viewer page, and instructions to create the NASA Blue Marble Next Generation from NASA dataset

As most technologies to provide Web viewing are HTTP based, it is quite easy to use a mass downloader to download individual tiles just like the Web viewing techonogy does. Rejoining them to recreate the full image is easy then. Because of copyrights and intellectual property, I will not disclose how to do, but so far I have successfully recreated images originating from the Google Maps API (easy) and Zoomify (harder), even multiple Gigapixel ones.

The most common format for tiles is JPEG, and the largest image I have is about 360x350 tiles of 256x256 pixels.

Needless to say, viewing very large images stored on a local disk is impressive, because of the speed compared to Web viewing. There is no delay when panning and zooming.

Large images on the Web

Giving a public access to gigapixel images requires that you have a way to make them accessible through the web.

There are quite a few technologies that allow this, here are the ones I know about:

1. The Google Maps API, written in Javascript + DHTML
2. Google Earth, a standalone application using HTTP to retrieve tiles.
3. Zoomify, written in Flash
4. FSI viewer, also written in Flash I think.

With these technologies, a few very large images can be viewed on your browser:

1. The Earth, on Google Maps, using a mix of satellite images and maps
   
2. The Blue Marble Next Generation Dataset from NASA on Yawah (resolution is 500 meters/pixel, so the complete image is about 86400x43200 pixels)
3. Digital photography, such as
• xRez (stitching a large array of digital images)
• The Gigapxl Project (scanning a very large format argentic film)
  
• Hal9000 Ikonos (stitching a large array of digital images)
  
• Scott Howard (Machu Picchu and Sydney By Night) (stitching a large array of digital images)

Other sites provide information on very large images, but do not make them available to the public:

• Max Lyons (who was the first to break the Gigapixel barrier for stitched digital images)
  

If you know other sites providing very large images, please comment.