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1.2 Gigapixel Image Test

By Andrew Mihal. Last update: 17 October 2004

Enblend 2.0 features a memory/disk balancing system that lets you control how much memory Enblend can use before it swaps to disk. If you are doing a small blending project, all of the data should fit in memory and the calculations should be fast. If you are doing a big project, Enblend will put frequently-used data in memory and swap the rest out to temporary files on disk. This is a little slower, but it enables you to blend very large projects. You are no longer limited by the amount of memory in your computer, or by address space limits on a 32-bit machine. The only limit should be the amount of disk space you have for temporary files, the length of time you are willing to let Enblend work, and the 4 gigabyte limit of the TIFF format.

To test this out, I ran Enblend on a 1.2 gigapixel image.

 

width = 40,000 pixels

 

 

height = 30,000 pixels

 

Image 1

Image 2

Output

The working assumption is that each horizontal row of images in the panorama has been previously blended. This is an easier job for Enblend because the overlap regions are smaller. In this test I am simulating blending two such horizontal rows together vertically. This is a good stress test because the overlap region is large. Each "row" is 10,000 pixels in height. The overlap region is 5,000 pixels in height. The total size of the overlap region alone is 200 megapixels!

Just to make things more interesting, these images are 16-bits per channel.

I performed this test on a 2.8 GHz Pentium IV, with 2 GB of memory, running Linux. I used the following options:

enblend -g -m 1500 -o gigapixel_out.tif gigapixel1.tif gigapixel2.tif

I limited Enblend's memory allocation to 1.5 GB to prevent the Linux kernel from swapping. Enblend used 10 blending levels. From start to finish, the job took 1 hour 8 minutes. About 27 GB of disk space was used for temporary files.

Note that without compression, each of these images would be 9.6 GB, which exceeds the limit of the TIFF format. However, these results show that Enblend is perfectly capable of blending projects right up to that limit.