jpeg-marker-stream

parse markers from a JPEG:

• SOI
• JFIF
• JFXX
• EXIF
• FPXR
• DQT
• DHT
• DRI
• SOF
• SOS
• DATA
• EOI

example

var jpeg = require('jpeg-marker-stream')
process.stdin.pipe(jpeg())
  .on('data', console.log)

output:

$ node exif.js < files/cactus.jpg 2>/dev/null | head -n20
{ type: 'SOI', start: 0, end: 2 }
{ type: 'JFIF',
  start: 2,
  end: 20,
  version: '1.1',
  density: { units: 'pixels per inch', x: 72, y: 72 },
  thumbnail: { x: 0, y: 0, data: <Buffer > } }
{ image: 
   { ImageWidth: 2560,
     ImageHeight: 1920,
     Make: 'google',
     Model: 'Nexus S',
     Orientation: 1,
     Software: 'JZO54K',
     ModifyDate: Fri Jun 19 2015 11:40:52 GMT+0100 (BST),
     YCbCrPositioning: 1,
     ExifOffset: 164 },
  thumbnail: 
   { ImageWidth: 320,
     ImageHeight: 240,

api

var jpeg = require('jpeg-marker-stream')

var stream = jpeg()

Return a transform stream jpeg that takes a binary stream of jpeg data as input and produces an object stream as output with the object types described below.

output object types

SOI

start of image

• marker.type = 'SOI'
• marker.start - offset of first byte
• marker.end - offset of last byte + 1

JFIF (APP0)

• marker.type = 'JFIF'
• marker.start - offset of first byte
• marker.end - offset of last byte + 1
• marker.version - jfif version string ('major.minor')
• marker.density.units - 'aspect', 'pixels per inch' or 'pixels per cm'
• marker.density.x - x density
• marker.density.y - y density
• marker.thumbnail.width - thumbnail width
• marker.thumbnail.height - thumbnail height
• marker.thumbnail.data - thumbnail data as a Buffer

JFXX (APP0)

• marker.type = 'JFXX'
• marker.start - offset of first byte
• marker.end - offset of last byte + 1
• marker.thumbnail.format - 'JPEG', 'PAL', or 'RGB'
• marker.thumbnail.width - thumbnail width (not available for 'JPEG'
• marker.thumbnail.height - thumbnail height (not available for 'JPEG')
• marker.thumbnail.data - thumbnail data as a Buffer
• marker.thumbnail.palette - thumbnail palette (for PAL thumbnails)

EXIF (APP1)

exif data

• marker.type = 'EXIF'
• marker.start - offset of first byte
• marker.end - offset of last byte + 1
• marker.image - exif image data
• marker.thumbnail - exif thumbnail data
• marker.exif - other exif data

FPXR (APP2)

exif extended data

• marker.type = 'FPXR'
• marker.start - offset of first byte
• marker.end - offset of last byte + 1

DQT

quantization table

• marker.type = 'DQT'
• marker.start - offset of first byte
• marker.end - offset of last byte + 1
• marker.tables - array of 64-byte quantization tables as buffers

DHT

huffman table

• marker.type = 'DHT'
• marker.start - offset of first byte
• marker.end - offset of last byte + 1
• marker.data - raw huffman data

DRI

define restart interoperability

• marker.type = 'DRI'
• marker.start - offset of first byte
• marker.end - offset of last byte + 1

SOS

start of scan, immediately preceeds compressed image data

• marker.type = 'SOS'
• marker.start - offset of first byte
• marker.end - offset of last byte + 1

SOF

start of frame

• marker.type = 'SOF'
• marker.start - offset of first byte
• marker.end - offset of last byte + 1
• marker.precision - bits of precision (8)
• marker.width - width of image (may or may not include padding)
• marker.height - height of image (may or may not include padding)
• marker.H0 - 2
• marker.V0 - 1 or 2

EOI

end of image

• marker.type = 'EOI'
• marker.start - offset of first byte
• marker.end - offset of last byte + 1

see also

• https://en.wikipedia.org/wiki/JPEG_File_Interchange_Format
• http://www.cipa.jp/std/documents/e/DC-008-2012_E.pdf

install

npm install jpeg-marker-stream

license

BSD