Many image formats are capable of storing supplementary technical and/or descriptive metadata alongside the actual image data in a file. Formats may be able to store standard metadata formats like EXIF, IPTC IIM, and XMP, and they may also define their own metadata formats. More than one such format may be present even within the same file.
When an image request is received—unless it calls for the full-sized unmodified source image—the image server will have to dynamically create and return a derivative image. As this is a whole new image, distinct from the source image, populating it with metadata would require an additional step.
When metadata.preserve is set to true in the configuration file, an effort will be made to copy metadata from source images into derivative images.
This currently does not work in all processors; see the Supported Features table for a breakdown. It also does not generally work across formats.
Metadata preservation tends to incur a performance penalty, and it is disabled by default.