Information in this article applies to:
- uScope Navigator (All Versions)
Article ID: NGN1076 — Created: 11 Oct 2017 — Reviewed: 22 Mar 2022
I keep hearing about pyramidal image sets and I'm not sure exactly what this means. So, I have two questions:
- What is a pyramidal image?
- Why would I want a pyramidal image (as opposed to a standard JPG image)?
- Does the uScope Navigator Software create pyramidal images?
- A pyramidal image is any image that is represented by a pyramid of images where higher images in the pyramid are smaller, lower resolution and lower images are larger, higher resolution. The pyramid is illustrated on the right.
- JPG images (as well as BMP, PNG, and other image file formats) are limited in size. When your computer displays a JPG or PNG image, that image is loaded into memory and shown on the screen. But, what happens if the size of the image is larger than your computer's memory?
That is where a pyramidal image is necessary. Since each layer of the pyramid is composed of small, square image tiles, the viewer only loads the tiles necessary to display the on-screen portion of the image. Google maps is a type of pyramidal image viewer.
Each layer in the Deep Zoom (pyramidal) image is composed of identically-sized square image tiles (typically, 256×256). The bottom layer of the pyramid is a 1-to-1 pixel mapping of the original image data to a mosaic of square image tiles as shown below.
- A layer that is higher in the pyramid is exactly ½ the dimension (¼ the area) of the layer immediately below.
- A layer that is lower in the pyramid is exactly 2× the dimension (4× the area) of the layer immediately above.
- The top layer of the pyramid is effectively a single pixel.
- The bottom layer of the pyramid is a 1:1 representation of the scanned image.
For more information on the folder format of the Deep Zoom images, refer to Job Folder Structure (uScope Navigator v4.5).
You may wish to refer to the Deep Zoom image format on the Microsoft web site for more details on its rationale and history.