Combine a photo (HEIC or JPEG) and a video into a file which Google Photos will recognize as a motion photo

combine_photo_video.sh

#!/bin/bash

# Inline XMP data
inline_xmp='<x:xmpmeta xmlns:x="adobe:ns:meta/" x:xmptk="Adobe XMP Core 5.1.0-jc003">
  <rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#">
    <rdf:Description rdf:about=""
        xmlns:GCamera="http://ns.google.com/photos/1.0/camera/"
        xmlns:Container="http://ns.google.com/photos/1.0/container/"
        xmlns:Item="http://ns.google.com/photos/1.0/container/item/"
        xmlns:xmpNote="http://ns.adobe.com/xmp/note/"
      GCamera:MotionPhoto="1"
      GCamera:MotionPhotoVersion="1"
      GCamera:MotionPhotoPresentationTimestampUs="0">
      <Container:Directory>
        <rdf:Seq>
          <rdf:li rdf:parseType="Resource">
            <Container:Item
              Item:Mime="image/jpeg"
              Item:Semantic="Primary"
              Item:Length="0"
              Item:Padding="0"/>
          </rdf:li>
          <rdf:li rdf:parseType="Resource">
            <Container:Item
              Item:Mime="video/mp4"
              Item:Semantic="MotionPhoto"
              Item:Length="0"
              Item:Padding="0"/>
          </rdf:li>
        </rdf:Seq>
      </Container:Directory>
    </rdf:Description>
  </rdf:RDF>
</x:xmpmeta>'

# Check if both photo and video files are provided and exist
if [ "$#" -lt 2 ] || [ ! -e "$1" ] || [ ! -e "$2" ]; then
  echo "Usage: $0 <photo_file> <video_file> [<output_file>]"
  echo "Both files must be provided and exist."
  exit 1
fi

temporary_file=$(mktemp /tmp/combined_image_XXXXXX.jpg)

# Check if the input file is in HEIC format
if [[ $(file -b --mime-type "$1") == "image/heic" ]]; then
    # Convert HEIC to JPEG using the "convert" command and save to a temporary file
    convert "$1" "$temporary_file"
else
    # If not HEIC, copy the JPEG to the temporary file
    cp "$1" "$temporary_file"
fi

# Create a temporary file for XMP data
xmp_file=$(mktemp /tmp/xmp_data_XXXXXX.xml)

# Write inline XMP data to the temporary XMP file
echo "$inline_xmp" > "$xmp_file"

# Check for existing XMP data and print a warning to stderr
existing_xmp_data=$(exiftool -a -xmp "$temporary_file" 2>&1)
if [ -n "$existing_xmp_data" ]; then
    echo "Warning: Existing XMP data found in $1. It will be replaced." >&2
fi

# Drop all XMP data in the JPEG file and add new XMP data
exiftool -q -XMP:all= "$temporary_file"
exiftool -q "-xmp<=$xmp_file" "$temporary_file"

# Determine output destination (stdout or specified file)
output_file="/dev/stdout"
if [ "$#" -eq 3 ]; then
    output_file="$3"
fi

# Concatenate the temporary file with XMP and the video file together and write to stdout
cat "$temporary_file" "$2" > "$output_file"

# Clean up temporary files
rm -f "$temporary_file" "$xmp_file"