don't buffer streams by default, opt-in for identify() and getters

README.md

@@ -99,6 +99,20 @@ gm(readStream, 'img.jpg')
   var writeStream = fs.createWriteStream('/path/to/my/resized.jpg');
   stdout.pipe(writeStream);
 });
+
+// when working with input streams and any 'identify'
+// operation (size, format, etc), you must pass "{bufferStream: true}" if
+// you also need to convert (write() or stream()) the image afterwards
+// NOTE: this temporarily buffers the image stream in Node memory
+var readStream = fs.createReadStream('/path/to/my/img.jpg');
+gm(readStream, 'img.jpg')
+.size({bufferStream: true}, function(err, size) {
+  this.resize(size.width / 2, size.height / 2)
+  this.write('/path/to/resized.jpg', function (err) {
+    if (!err) console.log('done');
+  });
+}
+
 ````
 
 ## Getting started

lib/command.js

@@ -76,8 +76,6 @@ module.exports = function (proto) {
       this.outname = format + ":-";
     }
 
-    var self = this;
-
     return this._spawn("gm", this.args(), false, callback);
   }
 
@@ -105,30 +103,35 @@ module.exports = function (proto) {
     * @return {Object} gm
     */
 
-  proto._spawn = function _spawn (bin, args, shouldBuffer, callback) {
+  proto._spawn = function _spawn (bin, args, bufferOutput, callback) {
     var proc = spawn(bin, args)
+      , cmd = bin + " " + args.map(utils.escape).join(' ')
       , self = this;
 
-    var cmd = bin + " " + args.join(' ');
-
     // pipe in the sourceStream if present
     if(self.sourceStream) {
 
+      if(!self.sourceStream.readable && !self.bufferStream) {
+        throw new Error("gm().stream() or gm().write() with a non-readable " +
+                        "stream. Pass \"{bufferStream: true}\" to identify() " +
+                        "or getter (size, format, etc...)");
+      }
+
       self.sourceStream.pipe(proc.stdin);
 
       // resume any buffered events from a previous step
-      if(self.streamBuffer) {
-        self.streamBuffer.resume();
+      if(self.buffer) {
+        self.buffer.resume();
 
       // if this isn't the last step, we need to buffer the
       // events on the input stream so we can use them again
-      } else if(shouldBuffer) {
-        self.streamBuffer = utils.buffer(self.sourceStream);
+      } else if(self.bufferStream) {
+        self.buffer = utils.buffer(self.sourceStream);
       }
     }
 
     // sometimes we need to buffer the output stream too
-    if(shouldBuffer) {
+    if(bufferOutput) {
       var stdout = ''
         , stderr = '';
 
@@ -164,7 +167,7 @@ module.exports = function (proto) {
               , this.sourceStream ? "-" : this.source
               , this._out
               , this.outname || "-"
-            );
+            ).filter(function(arg) { return !!arg });
   }
 
   /**

lib/getters.js

@@ -9,15 +9,16 @@ module.exports = function (proto) {
 
 ;['size', 'format', 'depth', 'color', 'res', 'filesize'].forEach(function (getter) {
 
-  proto[getter] = function (callback) {
-    var self = this;
+  proto[getter] = function (opts, callback) {
+    if(!callback) callback = opts, opts = {};
 
+    var self = this;
     if (self.data[getter]) {
       callback.call(self, null, self.data[getter]);
       return self;
     }
 
-    self.identify(function (err, stdout, stderr, cmd) {
+    self.identify(opts, function (err, stdout, stderr, cmd) {
       if (err) {
         return callback.call(self, err, stdout, stderr, cmd);
       }
@@ -29,11 +30,15 @@ module.exports = function (proto) {
   }
 });
 
-proto.identify = function identify (callback) {
+proto.identify = function identify (opts, callback) {
+  if(!callback) callback = opts, opts = {};
+
   var self = this;
 
   if (!callback) return self;
 
+  self.bufferStream = opts.bufferStream == true;
+
   if (self._identifying) {
     self._iq.push(callback);
     return self;

test/streamInGetter.js

@@ -0,0 +1,14 @@
+
+// gm - Copyright Aaron Heckmann <[email protected]> (MIT Licensed)
+
+var fs = require('fs');
+
+module.exports = function (_, dir, finish, gm) {
+
+  gm(fs.createReadStream(dir + '/original.jpg'), "original.jpg")
+  .size({bufferStream: true}, function(err, size) {
+    this.write(dir + '/streamInGetter.png', function streamInGetter (err){
+      finish(err);
+    });
+  });
+}