Large Panoramic Images

The last versions of PTViewer are fast enough to display a panorama in a rather large window: as a result the panoramic image becomes larger too. This can cause problems because, with most Java virtual machines, applets can use only a relatively small amount of memory, even if the computer has much more RAM available.

PTViewer loads the panoramic image in memory, so if there is not enough memory available it cannot show the image. In order to know the maximum size of an image that can be shown by PTViewer we need to know how much memory is available to the applet. An empiric test has lead to the following results (please keep in mind that I cannot guarantee that they are absolutely correct):

Windows, Internet Explorer, Microsoft VM No limits
Windows, Internet Explorer or Firefox, Sun VM 90 Mb
Windows, Opera, Sun VM 60 Mb
Linux Same as Windows
Mac OS 10.3.x 60 Mb

The memory (in bytes) needed to store an image can be computed with this formula:

w * h * 4

where w if the width of the image in pixel and h is the height. When loading a jpeg image PTViewer will need for a small time twice as much memory. PTViewer will also need memory for other data structures, so available memory will be less than the theoretical maximum.

Other memory is needed for the viewer window: the number of bytes is

w * h * 5

where w is the width of the viewer window and h is the height. As an example a 1024*768 window will require 3.5Mb.

A 4000*2000 pixel image requires 30.5 Mb (1 Mb = 1024*1024 bytes...) just to store it. PTViewer temporarily requires 61Mb to load it so that image cannot be loaded in a Mac, but it should be possible to load it in Windows.

How to show larger images

PTViewer home page