38.13.9 Image Cache

Emacs stores images in an image cache when it displays them, so it can display them again more efficiently. It removes an image from the cache when it hasn't been displayed for a specified period of time.

When an image is looked up in the cache, its specification is compared with cached image specifications using equal. This means that all images with equal specifications share the same image in the cache.

Variable: image-cache-eviction-delay

This variable specifies the number of seconds an image can remain in the cache without being displayed. When an image is not displayed for this length of time, Emacs removes it from the image cache.

If the value is nil, Emacs does not remove images from the cache except when you explicitly clear it. This mode can be useful for debugging.

Function: clear-image-cache &optional frame

This function clears the image cache. If frame is non-nil, only the cache for that frame is cleared. Otherwise all frames' caches are cleared.