gm: resize image if it is wider than 1000px

Question

I am trying to do some image manipulation via gm in collectionFS, because I need to read a stream and write it back to the same file, I have to use a temp-file - like shown below.

I want to check if the image is wider than 1000px. In this case it should be re-sized to 1000px.

Unfortunately this doesn't work, as I got the errors TypeError: Object [object Object] has no method 'pipe' and Error: gm().stream() or gm().write() with a non-readable stream.

var fs       = Npm.require('fs'),
    file     = Images.findOne({ _id: fileId }),
    read     = file.createReadStream('public'),
    filename = '/tmp/gm_' + Date.now(),
    temp     = fs.createWriteStream(filename);

if (method == 'resize') {
    // resize to 1000px, if image is bigger
    gmread = gm(read);
    gmread.size(function(err, size){
        if(size.width > 1000) {
            gmread.resize('1000').stream();
        }
    });
}

gmread.on('end', Meteor.bindEnvironment(function (error, result) {
    if (error) console.warn(error);

    var tmpread = fs.createReadStream(filename);
        write   = file.createWriteStream('public');

    tmpread.on('end', Meteor.bindEnvironment(function (error, result) { 
        if (error) console.warn(error);
    }));

    tmpread.pipe(write);
}));

gmread.pipe(temp);

Answer 1

I think the correct way in collectionFS is something like this:

var gmread = gm(readStream, fileObj.name());
gmread.size({bufferStream: true}, FS.Utility.safeCallback(function (error, size) {
    if (error) console.warn(error);
    else {
        if(size.width > 1000) gmread.resize('1000').stream().pipe(writeStream);
    }
}));

Mybe you want to put that into a transformWrite-function for your store...