Thursday, September 27, 2018

Converting from .heic to .jpg

A file with a .heic extension is an image using the new High Efficiency Image File Format (HEIF).

If somehow you've never heard about it, here are some sample files:

At the time of this writing, not all forensic tools fully support it. For instance, among the tools I have:

  • X-Ways Forensics (v19.7 SR-2) does no picture preview or metadata extraction. It has by the way a file carving algorithm for .heic images since version 19.5 Preview 2;
  • Magnet AXIOM (v2.5.1.11408) is able to preview the images but it doesn't extract (for now) any EXIF data from the HEIF format;
  • Cellebrite Physical Analyzer (v7.9.0.223) stands out from the crowd. If you have a set of images, you can easily view them and parse their metadata by simply choosing: File | Open (advanced) | Blank project | Folder | select the folder containing the pictures to analyze | Finish | Start decoding

Depending on the situation, it could be useful to use external viewers like XnView / CopyTrans HEIC or to convert .heic images to .jpg to make them "compatible" with other tools.

What follows is my method to do the conversion and can be used within a script.

Download and install ImageMagick (free - tested version on Win10: v7.0.8-12 7.0.8-28-Q16-x64-dll). Then open the command prompt and type:

magick SrcFile.heic DstFile.jpg

This will create a JPEG version of the HEIC file, but for some reason the EXIF metadata of the newly created file will be ignored and not parsed by many tools. After some trial and error, I managed to fix this issue with ExifTool (v11.10):

exiftool -overwrite_original -all= -TagsFromFile SrcFile.heic DstFile.jpg

The meaning of each option is the following:

-overwrite_original Overwrite the destination file without creating any backup copy of the destination file
-all= Strip off all metadata from the destination file
-TagsFromFile Copy all metadata tags from the SourceFile into the DestinationFile
SrcFile.heic Source file
DstFile.jpg Destination file

If you need to set the filesystem timestamps "last modified date" and "creation date" equal to the ones of the source .heic file, run ExifTool with these options:

exiftool -overwrite_original -TagsFromFile SrcFile.heic -FileModifyDate -FileCreateDate DstFile.jpg

For more details, you may check the ExifTool Documentation.

Additional resources on the HEIF format:

[UPDATE February 20, 2019]: Thanks to Phill Moore for letting me know that the metadata step described in the article is no longer needed when using the latest version of ImageMagick. Metadata is now properly added to the converted files.