How to check for corrupted jpg images using node.js and gm?

Question

I'd like to check for corrupted jpeg images and so far, straight in the command line I can use identify image.jpg which outputs:

image.jpg JPEG 1920x1200 1920x1200+0+0 8-bit sRGB 65.5KB 0.000u 0:00.009
identify: Premature end of JPEG file `image.jpg' @ warning/jpeg.c/JPEGWarningHandler/352.
identify: Corrupt JPEG data: premature end of data segment `image.jpg' @ warning/jpeg.c/JPEGWarningHandler/352.

or gm identify image.jpg which outputs:

image.jpg JPEG 1920x1200+0+0 DirectClass 8-bit 64.0Ki 0.000u 0:01
gm identify: Corrupt JPEG data: premature end of data segment (image.jpg).
    gm identify: Corrupt JPEG data: premature end of data segment (image.jpg).

It would be nice if I can use the gm package to get the corrupt JPEG data too. Simply using identify() outputs a lot of data, but nothing about corrupt data

gm('image.jpg')
.identify('%C',function (err, data) {
  if (!err) console.log(data)
  else console.error(err)
});

I've noticed this note in the readme:

If gm does not supply you with a method you need or does not work as you'd like, you can simply use gm().in() or gm().out() to set your own arguments.

I've tried something like this:

gm()
.command("identify") 
.in('image.jpg');

but I get no output so I'm probably doing it wrong.

I've also tried node-cmd:

cmd.get(
        'gm identify image.jpg',
        function(data){
            console.log('output: ',data)
        }
    );

but I only see the first line of the output.

What's the clean/recommended way of getting the multiline output from identify via gm package ? Otherwise, what's a node elegant solution to reading the full output of the identify command.

Update My guess is the string isn't displayed using gm because it comes through stderr , not stdout .

I've tested using a tweaked version of this snippet :

var spawn = require('child_process').spawn;

var bin = "identify"
var args = ['image.jpg'];
var cspr = spawn(bin, args);
cspr.stderr.on('data', function (data) {
    data += '';
    console.log(data.replace("\n", "\nstderr: "));
});
cspr.on('exit', function (code) {
    console.log('child process exited with code ' + code);
    process.exit(code);
});

What's the clean way of getting the stderr output via gm ?

Answer 1

I am very unqualified to say anything much about node or Javascript , but the following idea may get you up and running.

As I understand it, you want to use identify but are unable to capture its stderr . We do know how to capture the stderr of convert though. So, the suggestion is to invoke convert in a way it mimics the functionality of identify but with the calling interface of convert .

You can do that like this:

gm convert someImage.jpg info:-

optionally adding in -verbose if needed.

That looks like this in node apparently!

gm(jpgPath)
  .command('convert')
  .write('out.png', function(err, stdout,stderr){   
     console.log("stderr",stderr);
});