The Code Behind Deep Zoom Images
At the heart of every Deep Zoom Image file lies a tiled image pyramid that allows the rendering engine to pick and choose only the data that is required for a particular view. Each level is significantly smaller than the next, and is loaded as soon as it becomes available. The smooth Seadragon experience is created by progressively loading each new resolution level and seamlessly blending between them.
These tiles range from a 1x1 single pixel, all the way up to the full resolution of the original image, comprised of individual 256x256 tiles. Each progressively lower resolution level of the pyramid is half the height and half the width of the previous level. When you create your own Deep Zoom Image or Collection, regardless of what tool you use, the images and folders that are generated make up this tiled image pyramid. The diagram below illustrates that with each level taking up effectively one-fourth of the previous level, the total overhead is no more than 33%. With the performance benefits of being able to access tiles as they become available, this more than compensates for the extra data needed to be stored.
To learn more about Seadragon images, see the
File Formats page.