nodejs gm using stream twice

Question

I need to make two resized images from another one.

var fs = require('fs')
  , gm = require('gm')
  , async = require('async');

var worker = function(filename) {
    img = gm(fs.createReadStream(filename));
    img.flip();

    this.run = function() {
        async.series([
            function(callback) {
                img.resize(640, 480);
                img.toBuffer(function(err, buffer) {
                    if (err) {
                        callback(err);
                        return;
                    }
                    callback(null, true);
                })
            },
            function(callback) {
                img.resize(320, 240);
                img.toBuffer(function(err, buffer) {
                    if (err) {
                        callback(err);
                        return;
                    }
                    callback(null, true);
                })
            },
        ],
        function(err, results) {
            console.log(err, results);
        });
    };
}

new worker('test.jpg').run();

This code generates error:

Error: gm().stream() or gm().write() with a non-readable stream.

If I replace fs.createReadStream with a filename than everything works just fine. It looks like gm doesn't store the source image from stream in it's internal buffer. Is it a bug or I should know something else about using it in proper way?

Notice: Async is used because in real project I need both results to perform other actions with them.

I'm already not using it, but it requires to think about copying data from stream into buffer, making code bigger. Anyway, if gm library allows writing gm(stream).resize(...).stream(callback).resize(...).stream(callback) than it should work with streams and files in similar way without workarounds. — Lisio, Jun 30 '13 at 22:11

score 0 · Answer 1 · answered Jul 16 '13 at 11:39

try this, i dont think you need to use writeStreams in this case:

gm(imagePath)
  .resize(640, 480)
  .autoOrient()
  .flip()
  .write(newImagePath, function(e) {
  if (e) throw e;
  gm(newImagePath)
    .resize(320, 240)
    .write(newImagePathSmall, function(e) {
    if (e) throw e;
    console.log('resized successfuly');
  });
});

nodejs gm using stream twice

1 Answers1