kim
0.31.0indexedRead and write image metadata across formats, including EXIF/IPTC/XMP; lossless single-byte rotation, thumbnail updates, RAW preview extraction and high-level photo summaries.
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Kim - Kotlin Image Metadata
Kim is a Kotlin Multiplatform library for reading and writing image metadata.
Features
Installation
implementation("de.stefan-oltmann:kim:0.32.0")
For the targets wasmJs & js you also need to specify this:
implementation(npm("pako", "2.1.0"))
Sample usages
Read metadata
Kim.readMetadata() takes kotlin.ByteArray on all platforms and depending on
the platform also kotlinx.io.files.Path, kotlinx.io.Source (for usage with Ktor) & ByteReadChannel,
java.io.File, , (iOS) and paths.
val bytes: ByteArray = loadBytes()
val metadata = Kim.readMetadata(bytes)
/* ImageMetadata has a proper toString() similar to the output of ExifTool */
println(metadata)
val orientation = metadata.findShortValue(TiffTag.TIFF_TAG_ORIENTATION)
println("Orientation: $orientation")
val takenDate = metadata.findStringValue(ExifTag.EXIF_TAG_DATE_TIME_ORIGINAL)
println("Taken date: $takenDate")
Create high level summary object
This creates an instance of MetadataSummary. It contains the following:
- Image size
- Orientation
- Date taken
- GPS coordinates
- Camera make & model
- Lens make & model
- ISO, Exposure time, F-Number, Focal length
- Image title & description
val bytes: ByteArray = loadBytes()
val summary = Kim.readMetadata(bytes).convertToSummary()
Change orientation using low level API
val inputFile = File("myphoto.jpg")
val outputFile = File("myphoto_changed.jpg")
val metadata = Kim.readMetadata(inputFile)
val outputSet: TiffOutputSet = metadata.exif?.createOutputSet() ?: TiffOutputSet()
val rootDirectory = outputSet.getOrCreateRootDirectory()
rootDirectory.removeField(TiffTag.TIFF_TAG_ORIENTATION)
rootDirectory.add(TiffTag.TIFF_TAG_ORIENTATION, 8)
OutputStreamByteWriter(outputFile.outputStream()).use { outputStreamByteWriter ->
JpegRewriter.updateExifMetadataLossless(
byteReader = JvmInputStreamByteReader(inputFile.inputStream(), inputFile.length()),
byteWriter = outputStreamByteWriter,
outputSet = outputSet
)
}
See the example project for more details.
Change orientation using Kim.update() API
val bytes: ByteArray = loadBytes()
val newBytes = Kim.update(
bytes = bytes,
update = MetadataUpdate.Orientation(TiffOrientation.ROTATE_RIGHT)
)
See AbstractUpdaterTest for more samples.
Update thumbnail using Kim.update() API
val bytes: ByteArray = loadBytes()
val thumbnailBytes: ByteArray = loadThumbnailBytes()
val newBytes = Kim.updateThumbnail(
bytes = bytes,
thumbnailBytes = thumbnailBytes
)
Using Java
See the Java example project how to use Kim in Java projects.
Limitations
- Inability to update EXIF, IPTC, and XMP in JPG files simultaneously.
- Does not read the image size and orientation for HEIC, AVIF & JPEG XL.
- Does not read brotli compressed metadata of JPEG XL due to missing brotli KMP libs.
- MakerNote support is experimental and limited.
- Can't extract preview image of ORF as offsets are burried into MakerNote.
- Can't identify lens info of NEF, ARW, RW2 & ORF because this is constructed from MakerNote fields.
- Missing image size for RW2 as this is also burried in MakerNotes.
- There is right now no convienient tooling for GeoTiff like there is for GPS.
Regarding HEIC & AVIF metadata
In the processing of HEIC and AVIF files, we handle them as standard ISOBMFF-based files, adhering rigorously to the EIC/ISO 14496-12 specification. To preempt potential legal issues, we intentionally omit certain boxes outlined in the HEIC specification, notably the image size ("ispe") and image rotation ("irot") boxes. This approach extends to AVIF images, as they repurpose the same boxes.
Contributions
Contributions to Kim are welcome! If you encounter any issues, have suggestions for improvements, or would like to contribute new features, please feel free to submit a pull request.
Acknowledgements
- JetBrains for making Kotlin.
- Apache Software Foundation for making Apache Commons Imaging.
- Drew Noakes for making metadata-extractor.
- Phil Harvey for making .
License
This code is under the Apache License 2.0.
See the NOTICE.txt file for required notices and attributions.