thumbsup/src/components/exiftool

exiftool-batch

Process a batch of files through exiftool and stream the results

Usage

const exiftool = require('./exiftool-batch/parallel')
const stream = exiftool.parse('./photos', [
  'IMG_000001.jpg',
  'IMG_000002.jpg',
  'IMG_000003.jpg'
])
stream.on('data', entry => console.log(`Processed ${entry.SourceFile}`))
stream.on('end', () => console.log('Finished'))

The number of parallel exiftool processes defaults to the CPU count. It can be overridden by exiftool.parse(root, files, count).

Each stream entry will be an object in the following format.

{
  SourceFile: 'NewYork/IMG_5364.jpg',
  File: {
    FileSize: '449 kB',
    MIMEType: 'image/jpeg',
    /* ... */
  },
  EXIF: {
    Orientation: 'Horizontal (normal)',
    DateTimeOriginal: '2017:01:07 13:59:56',
    /* ... */
  },
  Composite: {
    GPSLatitude: '+51.5285578',
    GPSLongitude: -0.2420248,
    /* ... */
  }
}

Stream structure

Some notes on the structure:

• the SourceFile property is a relative path to the root folder given to parse()
• the format is identical to the raw JSON exiftool output
  • the name of the groups and tags are exactly as documented at http://www.sno.phy.queensu.ca/~phil/exiftool/TagNames/index.html
  • it doesn't try to parse date strings, and doesn't assume timezones when absent
  • it doesn't fix GPS format oddities, like -10.000 (number) and "+10.000" (string)
  • it doesn't merge similar fields together, like EXIF:ImageDescription and IPTC:Caption-Abstract

Performance

• uses exiftool in batch mode, instead of spawning 1 instance per file
• runs 1 exiftool process per core to speed-up parsing

The following stats were captured while processing a large number of photos stored on an SSD drive:

Metric	Value
Number of photos	10,000
Total time	30 sec
Peak throughput	300 photos / sec

Process	CPU (4 cores)	RAM
Node	25%	70 MB
Exiftool	85% per instance	20 MB per instance
Total	365%	150 MB