Update caching documentation
@@ -17,6 +17,8 @@ Android 5.0 and newer has much improved memory management than earlier versions,
Your app should [clear this cache](#clearing-the-cache) when it is backgrounded.
+For non-static image formats or custom image formats, the Bitmap cache can hold any decoded image data by extending the `CloseableImage` class. See [customizing image formats](customizing-image-formats.html) for more details.
+
#### 2. Encoded memory cache
This cache stores images in their original compressed form. Images retrieved from this cache must be decoded before display.
