GS Firebase function can't set offset?

Question

I am using firebase functions to crop certain area of pdf and convert them to image using ghostscript [The wrapper https://www.npmjs.com/package/node-gs and compiled version of gs v9.2 "https://github.com/sina-masnadi/node-gs/tarball/master" ]

and this is the code i am using :

const functions = require('firebase-functions');
const { Storage } = require('@google-cloud/storage');
const gcs = new Storage();
const spawn = require('child-process-promise').spawn;
const path = require('path');
const os = require('os');
const fs = require('fs');
var gs = require('gs');


const THUMB_MAX_HEIGHT = 200;
const THUMB_MAX_WIDTH = 200;
const THUMB_SUFFIX = '-thumb';

//This function triggers whenever any pdf is uploaded to the firebase storage
//and attempts to generate

exports.makePreviews = functions.storage.object().onFinalize(async (object, event) => {

  //Checking for pdf files
  if (!object.name.endsWith('.pdf')) return false;

  const filePath = object.name;

  //slicing name and path
  const splitFileName = object.name.split(".");
  console.log(splitFileName);
  const fileID = splitFileName;

  //creating temporary path strings for gcp file system
  const fileName = path.basename(filePath);
  const tempFilePath = path.join(os.tmpdir(), fileName);

  const newName1 = path.basename(filePath, '.pdf') + '01.jpeg';
  const tempNewPath1 = path.join(os.tmpdir(), newName1);

  const newName2 = path.basename(filePath, '.pdf') + '02.jpeg';
  const tempNewPath2 = path.join(os.tmpdir(), newName2);

  const thumbName = path.basename(filePath, '.pdf') + THUMB_SUFFIX + '.jpeg';
  const tempThumbPath = path.join(os.tmpdir(), thumbName);


  //downloading file from firebase storage
  const bucket = gcs.bucket(object.bucket);

  return bucket.file(filePath).download({
    destination: tempFilePath
  }).then(async () => {
    console.log('PDF downloaded locally to', tempFilePath);

    //generating two preview JPEGS
    await new Promise((resolve, reject) => {
      gs()
        .safer()
        .batch()
        .nopause()
        .option('-dTextAlphaBits=4')
        .option('-dGraphicsAlphaBits=4')
        .option('-dDEVICEWIDTHPOINTS=238')
        .option('-dDEVICEHEIGHTPOINTS=149.5')
        .option('-dFIXEDMEDIA')
        .res(600)
        .option('-dDownScaleFactor=2')
        .executablePath('gs')
        .device('jpeg')
        .output(tempNewPath2)
        .option('-c "<</PageOffset[-308.5 40]>> setpagedevice"')
        .option('-sPDFPassword=01011977')
        .input(tempFilePath)
        .exec((err, stdout, stderr) => {
          if (!err) {
            console.log('Part One Exceuted');
            bucket.upload(tempNewPath1, {
              destination: 'files/' + fileID + '.jpeg'
            }).then(() => {
              console.log('stdout', stdout);
              console.log('stderr', stderr);
            }).catch(err => {
              console.log(err);
            });
            resolve();
          } else {
            console.log('gs error:', err);
            reject(err);
          }
        });
    });

    await new Promise((resolve, reject) => {
      gs()
        .safer()
        .batch()
        .nopause()
        .option('-dTextAlphaBits=4')
        .option('-dGraphicsAlphaBits=4')
        .option('-dDEVICEWIDTHPOINTS=238')
        .option('-dDEVICEHEIGHTPOINTS=149.5')
        .option('-dFIXEDMEDIA')
        .res(600)
        .option('-dDownScaleFactor=2')
        .executablePath('gs')
        .device('jpeg')
        .output(tempNewPath2)
        .option('-c "<</PageOffset[-308.5 40]>> setpagedevice"')
        .option('-sPDFPassword=01011977')
        .input(tempFilePath)
        .exec((err, stdout, stderr) => {
          if (!err) {
            console.log('gs Part two excuted');
            bucket.upload(tempNewPath1, {
              destination: 'files/' + fileID + '-2.jpeg'
            }).then(() => {
              console.log('stdout', stdout);
              console.log('stderr', stderr);
            })
              .catch(err => {
                console.log(err);
              });
            resolve();
          } else {
            console.log('gs error:', err);
            reject(err);
          }
        });
    });

    //generating thumbnail from the first JPEG
    return spawn('convert', [tempNewPath1, '-thumbnail', `${THUMB_MAX_WIDTH}x${THUMB_MAX_HEIGHT}>`, tempThumbPath], {
      capture: ['stdout', 'stderr']
    });

  }).then(async () => {
    console.log('PNG created at', tempNewPath1 + 'and' + tempNewPath2);
    console.log('Thumbnail created at', tempThumbPath);

    //uploading the files back to firebase storage
    return bucket.upload(tempThumbPath, {
      destination: 'files/' + fileID + 'thumb.jpeg'
    });


  }).then(() => {
    //once the files have been uploaded delete the local temporary 
    //files to free up disk space.
    fs.unlinkSync(tempNewPath1);
    fs.unlinkSync(tempNewPath2);
    fs.unlinkSync(tempThumbPath);
    return fs.unlinkSync(tempFilePath);
  }).catch((err) => {
    console.log('exception:', err);
    return err;
  });
});

deploying the above code, The Log:

[ 'PAN_01011977', 'pdf' ]

PDF downloaded locally to /tmp/PAN_01011977.pdf

gs command: -dSAFER,-dBATCH,-dNOPAUSE,-dTextAlphaBits=4,-dGraphicsAlphaBits=4,-dDEVICEWIDTHPOINTS=238,-dDEVICEHEIGHTPOINTS=149.5,-dFIXEDMEDIA,-r600,-dDownScaleFactor=2,-sDEVICE=jpeg,-sOutputFile=/tmp/PAN_0101197702.jpeg,-c "<</PageOffset[-308.5 40]>> setpagedevice",-sPDFPassword=01011977,/tmp/PAN_01011977.pdf

Part One Exceuted

gs command: -dSAFER,-dBATCH,-dNOPAUSE,-dTextAlphaBits=4,-dGraphicsAlphaBits=4,-dDEVICEWIDTHPOINTS=238,-dDEVICEHEIGHTPOINTS=149.5,-dFIXEDMEDIA,-r600,-dDownScaleFactor=2,-sDEVICE=jpeg,-sOutputFile=/tmp/PAN_0101197702.jpeg,-c "<</PageOffset[-308.5 40]>> setpagedevice",-sPDFPassword=01011977,/tmp/PAN_01011977.pdf

{ Error: ENOENT: no such file or directory, stat '/tmp/PAN_0101197701.jpeg'
  errno: -2,
  code: 'ENOENT',
  syscall: 'stat',
  path: '/tmp/PAN_0101197701.jpeg' }

gs Part two excuted

{ Error: ENOENT: no such file or directory, stat '/tmp/PAN_0101197701.jpeg'
  errno: -2,
  code: 'ENOENT',
  syscall: 'stat',
  path: '/tmp/PAN_0101197701.jpeg' }

and the error :

and the error log

exception: { ChildProcessError: `convert /tmp/PAN_0101197701.jpeg -thumbnail 200x200> /tmp/PAN_01011977-thumb.jpeg` failed with code 1
    at ChildProcess.<anonymous> (/srv/node_modules/child-process-promise/lib/index.js:132:23)
    at emitTwo (events.js:126:13)
    at ChildProcess.emit (events.js:214:7)
    at maybeClose (internal/child_process.js:915:16)
    at Process.ChildProcess._handle.onexit (internal/child_process.js:209:5)
  name: 'ChildProcessError',
  code: 1,
  childProcess: 
   ChildProcess {
     domain: 
      Domain {
        domain: null,
        _events: [Object],
        _eventsCount: 1,
        _maxListeners: undefined,
        members: [Array] },
     _events: { error: [Function], close: [Function] },
     _eventsCount: 2,
     _maxListeners: undefined,
     _closesNeeded: 3,
     _closesGot: 3,
     connected: false,
     signalCode: null,
     exitCode: 1,
     killed: false,
     spawnfile: 'convert',
     _handle: null,
     spawnargs: 
      [ 'convert',
        '/tmp/PAN_0101197701.jpeg',
        '-thumbnail',
        '200x200>',
        '/tmp/PAN_01011977-thumb.jpeg' ],
     pid: 14,
     stdin: 
      Socket {
        connecting: false,
        _hadError: false,
        _handle: null,
        _parent: null,
        _host: null,
        _readableState: [Object],
        readable: false,
        domain: [Object],
        _events: [Object],
        _eventsCount: 2,
        _maxListeners: undefined,
        _writableState: [Object],
        writable: false,
        allowHalfOpen: false,
        _bytesDispatched: 0,
        _sockname: null,
        _pendingData: null,
        _pendingEncoding: '',
        server: null,
        _server: null,
        _idleNext: null,
        _idlePrev: null,
        _idleTimeout: -1,
        [Symbol(asyncId)]: 4540,
        [Symbol(bytesRead)]: 0 },
     stdout: 
      Socket {
        connecting: false,
        _hadError: false,
        _handle: null,
        _parent: null,
        _host: null,
        _readableState: [Object],
        readable: false,
        domain: [Object],
        _events: [Object],
        _eventsCount: 3,
        _maxListeners: undefined,
        _writableState: [Object],
        writable: false,
        allowHalfOpen: false,
        _bytesDispatched: 0,
        _sockname: null,
        _pendingData: null,
        _pendingEncoding: '',
        server: null,
        _server: null,
        _idleNext: null,
        _idlePrev: null,
        _idleTimeout: -1,
        write: [Function: writeAfterFIN],
        [Symbol(asyncId)]: 4541,
        [Symbol(bytesRead)]: 0 },
     stderr: 
      Socket {
        connecting: false,
        _hadError: false,
        _handle: null,
        _parent: null,
        _host: null,
        _readableState: [Object],
        readable: false,
        domain: [Object],
        _events: [Object],
        _eventsCount: 3,
        _maxListeners: undefined,
        _writableState: [Object],
        writable: false,
        allowHalfOpen: false,
        _bytesDispatched: 0,
        _sockname: null,
        _pendingData: null,
        _pendingEncoding: '',
        server: null,
        _server: null,
        _idleNext: null,
        _idlePrev: null,
        _idleTimeout: -1,
        write: [Function: writeAfterFIN],
        [Symbol(asyncId)]: 4542,
        [Symbol(bytesRead)]: 232 },
     stdio: [ [Object], [Object], [Object] ] },
  stdout: '',
  stderr: 'convert-im6.q16: unable to open image `/tmp/PAN_0101197701.jpeg\': No such file or directory @ error/blob.c/OpenBlob/2701.\nconvert-im6.q16: no images defined `/tmp/PAN_01011977-thumb.jpeg\' @ error/convert.c/ConvertImageCommand/3258.\n' }

Error serializing return value: TypeError: Converting circular structure to JSON


Function execution took 9561 ms, finished with status: 'ok'

The problem is in using the below option in gs without this the function works but it didn't crops the pdf just converts to full page image.

  //.option('-c "<</PageOffset [ -64.2 40 ]>> setpagedevice"')
  //.option('-c "<</PageOffset [ -308.5 40 ]>> setpagedevice"')

How can i use the above option ?

Edit

Tried to terminate -c with -f but no luck

$ node index.js
gs command: -dSAFER,-dBATCH,-dNOPAUSE,-dTextAlphaBits=4,-dGraphicsAlphaBits=4,-dDEVICEWIDTHPOINTS=238,-dDEVICEHEIGHTPOINTS=149.5,-dFIXEDMEDIA,-r150,-dDownScaleFactor=2,-sPDFPassword=01011977,-sDEVICE=jpeg,-sOutputFile=/home/jcol/Desktop/gs_offline/functions/output.jpeg,-c <</PageOffset[-64.2 40]>>setpagedevice,-f,/home/jcol/Desktop/gs_offline/functions/pan.pdf
Suceess
GPL Ghostscript 9.20 (2016-09-26)
Copyright (C) 2016 Artifex Software, Inc.  All rights reserved.
This software comes with NO WARRANTY: see the file PUBLIC for details.
Processing pages 1 through 1.
Page 1
Loading NimbusSans-Regular font from %rom%Resource/Font/NimbusSans-Regular... 4244908 2808684 2600016 1250276 3 done. 

Answer 1

In the absence of an example file (and ideally the actual command line being sent to Ghostscript) as well as the lack of the back channel output (stout and stderr) the only observation I can make is that the 'option' you refer to (actually a piece of PostScript programming) introduces PostScript input with the -c switch but does not terminate it with -f. That means anything which folows this on the comand line will be treated as more PostScript, which is likely to either lead to an error or a 'hang', awaiting more input.

Answer 2

For Future Readers

And For Newbies like ME

There was some confusion in using libraries in NODEJS as i was new to it.

Firstly i was using some gs-wrapper from some tutorials which was not on NPM and that was the cause of the error as that didn't for some reason supported commands.

After some Research i came to Node-gs from npm and i checked Node-GS API at their page in NPM and it had dedicated option for command option.

Now why i posted this Answer :

The NODE-GS library is the only to support serverless architecture like Firebsae Functions. But error handling in this is worst as this only spawns Ghostscirpt directly from the Executable.

For Example if you provide wrong password for PDF then the library just going to push Ghostscript Unrecoverable Error in error Message.

(I know if you are using Ghostscirpt in serverless functions you're smart enough to check if password is correct or not on client side but just for example)

At the time of writing this i found Ghostscript4JS for NODE which uses C++ API of Ghostscript but unfortunately this library doesn't supports serverless architecture as the library depends on system installed Ghostscirpt but the developer said it has some some plans on it.

Check if the library now supported serverless Architecture.

And in the end the struggle as a newbie i had to go through was find portable version of Ghostscirpt to use with NODE-GS and you can find it here Ghostscript Releases

For Firebase Function Users Firebase functions is built upon Ubuntu Bionic 18.04 arch x64 so you have to use x86_64 version of Ghostscript and The latest at the time of writing is Ghostscript 9.52

B-Bye :)