node.js - How to composite multiple images in one stream -

i'm trying composite multiple images single stream piped response. i'm using node.js , graphicsmagick node @ https://github.com/aheckmann/gm.

if i'm compositing 2 images stream works fine , example shows two/thirds of final composite expected. here code:

app.get('/call_2image_stream', function(req, res){      res.writehead(200, {'content-type' : 'image/png'});     var path = (__dirname + '/test_folder/happy_right.png');     var path2 = (__dirname + '/test_folder/happy_left.png');     gm(path)       .composite(path2)       .stream('png')       .pipe(res); }) 

this works great in postman

but when try , composite 3 images doesn't fill in bottom part of picture correctly intended. code this:

app.get('/call_3image_stream', function(req, res){      res.writehead(200, {'content-type' : 'image/png'});     var path = (__dirname + '/test_folder/happy_bottom.png');     var path2 = (__dirname + '/test_folder/happy_right.png');     var path3 = (__dirname + '/test_folder/happy_left.png');     gm(path)       .composite(path2)       .composite(path3)       .stream('png')       .pipe(res); }) 

i can't figure out why output this:

figured out great answer write here: https://stackoverflow.com/a/20611669/4447761 shout out ryan wu!

here final code

app.get('/final_code', function(req, res){     res.writehead(200, {'content-type' : 'image/png'});     gm()      .in('-page', '+0+0')      .in(__dirname + '/test_folder/happy_right.png')      .in('-page', '+0+0')       .in(__dirname + '/test_folder/happy_left.png')      .in('-page', '+0+0')       .in(__dirname + '/test_folder/happy_bottom.png')      .mosaic()      .stream('png')      .pipe(res); })