Image Optimizer
The Image Optimizer is a feature of The Forge. It automatically transforms image assets so that they load faster and perform better for your players.
In the past, this feature also allowed in-app image flipping, and blurring. This feature is currently limited due to a change in CDN (Content Delivery Network). We hope to restore functionality in a future update.
Currently, the image optimizer automatically converts images into better performing .webp files, and will use those over the original file if there is a significant decrease in the original file size. At the moment, it does not resize the pixel dimensions of an image.
GPU Texture limit avoidance
Many Game Masters like to use high resolution maps for their games, or simply use a map without thinking about its resolution. To be clear, this means maps with significant pixel length or width- not the actual file size of the map.
Unfortunately, while these images may work for some users (such as the GM), they may not load for all players, or across all machines accessing the game. There is a base limitation of 16384x16384 pixels to load a map at all within Foundry VTT, due to underlying WebGL technology. But most browsers will automatically detect the performance of a user’s PC, and prevent images from being loaded past a certain size.
Therefore, while an image may load on a user’s particularly powerful PC/laptop, it may fail to load on another user’s weaker device. Typically, these size limitations are around 16384x16384, 8192x8192, or 4096x4096. The latter is most common on users accessing Foundry through integrated graphic cards found within laptops.
To prevent this, we recommend users keep images at or below a resolution of 4096 at any pixel dimension- this will ensure that the image will load for everyone.
A Workaround
If a GM wishes to keep using high quality maps, but keep them functioning for users with weaker laptops, a map can be split up into two or more smaller images, and then placed as tiles within Foundry VTT. This will neatly sidestep potential canvas limitations.
However, it should be noted that these tiles will not perform as well as scene images. Additionally, large maps like these will cause other performance issues, especially when using dynamic lighting alongside them. For users with already weak machines, this can greatly interfere with the base functionality of Foundry VTT. We recommend caution when taking this approach.