Imagemagick pipes #imagemagick #pipe

ext-pipe.js

const fs = require('fs')
const path = require('path')
const spawn = require('child_process').spawn

// Gradient overlay example
// http://www.imagemagick.org/script/command-line-processing.php#input

const photoWriteStream = fs.createWriteStream(
  path.join(__dirname, '/img-02-js-out.jpg')
)

const photoReadStream = fs.createReadStream(path.join(__dirname, 'img-02.jpg'))

const gradientChildProcess = spawn('convert', [
  '-size',
  '1500x120',
  'gradient:',
  'miff:-'
])

const convertChildProcess = spawn(
  // 'magick',
  'convert',
  [
    'jpg:-',
    'fd:3',
    '-gravity',
    'South',
    '-alpha',
    'off',
    '-compose',
    'CopyOpacity',
    '-composite',
    '-background',
    'white',
    '-alpha',
    'remove',
    'jpg:-'
  ],
  {
    stdio: ['pipe', 'pipe', 2, 'pipe'] // 2 - share stderr
  }
)

photoReadStream.pipe(convertChildProcess.stdin)
gradientChildProcess.stdout.pipe(convertChildProcess.stdio[3])

convertChildProcess.stdout.pipe(photoWriteStream)

std-pipe.js

var fs = require('fs')
var spawn = require('child_process').spawn
var request = require('request')

var photoStream1 = request('http://www.imagemagick.org/image/wizard.jpg')
var outFileStream = fs.createWriteStream(__dirname + '/temp-convert.jpg')

var convert = spawn('convert', ['-', '-append', '-'], { 
  stdio: ['pipe', 'pipe', 2] 
})

photoStream1.pipe(convert.stdin)
convert.stdout.pipe(outFileStream)

// OK
// temp-convert.jpg contains image