jpeg-metadata

Reads and re-attaches a JPEG’s metadata segments.

Re-encoding an image through a canvas keeps only pixels: EXIF, GPS, XMP and the ICC profile are all dropped by construction, because the canvas holds decoded samples and nothing else. These helpers lift the metadata segments off the original bytes so they can be spliced back into the re-encoded JPEG.

Functions

Function Description

extractJpegMetadataSegments Extracts the metadata segments of a JPEG. Returns each matching segment whole — marker, length and payload — so injectJpegMetadataSegments can splice it into another JPEG untouched. Only the segments that carry metadata are returned: the EXIF and XMP APP1s and the ICC profile APP2. APP0 (JFIF) is deliberately left behind, because the re-encoded JPEG writes its own. Returns an empty array for anything that is not a JPEG, including a truncated or malformed one — a caller that cannot preserve metadata should carry on without it rather than fail.

injectJpegMetadataSegments Splices metadata segments into a JPEG. The segments go directly after the SOI and the re-encoded JPEG’s own APP0, which is where a reader expects to find them. Every copied EXIF block has its orientation tag reset to upright. The canvas decode already applied the original orientation to the pixels, so carrying the tag across verbatim would rotate the image a second time — the one piece of metadata that is wrong to preserve as-is.

Function	Description
extractJpegMetadataSegments	Extracts the metadata segments of a JPEG. Returns each matching segment whole — marker, length and payload — so injectJpegMetadataSegments can splice it into another JPEG untouched. Only the segments that carry metadata are returned: the EXIF and XMP `APP1`s and the ICC profile `APP2`. `APP0` (JFIF) is deliberately left behind, because the re-encoded JPEG writes its own. Returns an empty array for anything that is not a JPEG, including a truncated or malformed one — a caller that cannot preserve metadata should carry on without it rather than fail.
injectJpegMetadataSegments	Splices metadata segments into a JPEG. The segments go directly after the `SOI` and the re-encoded JPEG’s own `APP0`, which is where a reader expects to find them. Every copied EXIF block has its orientation tag reset to upright. The canvas decode already applied the original orientation to the pixels, so carrying the tag across verbatim would rotate the image a second time — the one piece of metadata that is wrong to preserve as-is.