Use shrink-on-load for JPEG images, partially implementing #4. Switch to new vip_ methods from legacy im_ methods. Large performance gains all round.

.gitignore

@@ -13,5 +13,6 @@ results
 build
 node_modules
 tests/output.jpg
+tests/output.png
 
 npm-debug.log

.travis.yml

@@ -1,8 +0,0 @@
-language: node_js
-node_js:
-  - "0.11"
-  - "0.10"
-before_install:
- - sudo apt-get update -qq
- - sudo apt-get install -qq libvips-dev imagemagick
- - sudo ln -s /usr/lib/pkgconfig/vips-7.26.pc /usr/lib/pkgconfig/vips.pc

README.md

@@ -7,28 +7,23 @@ _adj_
 3. shrewd or astute: a sharp bargainer. 
 4. (Informal.) very stylish: a sharp dresser; a sharp jacket. 
 
-The typical use case for this high speed Node.js module is to convert a large JPEG image to smaller JPEG images of varying dimensions.
+The typical use case for this high speed Node.js module is to convert large JPEG and PNG images to smaller JPEG and PNG images of varying dimensions.
 
-It is somewhat opinionated in that it only deals with JPEG images, always obeys the requested dimensions by either cropping or embedding and insists on a mild sharpen of the resulting image.
+It is somewhat opinionated in that it only deals with JPEG and PNG images, always obeys the requested dimensions by either cropping or embedding and insists on a mild sharpen of the resulting image.
 
 Under the hood you'll find the blazingly fast [libvips](https://github.com/jcupitt/libvips) image processing library, originally created in 1989 at Birkbeck College and currently maintained by the University of Southampton.
 
-Performance is 4x-8x faster than ImageMagick and 2x-4x faster than GraphicsMagick, based mainly on the number of CPU cores available.
+Performance is 12x-15x faster than ImageMagick and 4x-6x faster than GraphicsMagick, based mainly on the number of CPU cores available.
 
 ## Prerequisites
 
 * Node.js v0.8+
 * node-gyp
-* libvips-dev 7.28+
+* [libvips](https://github.com/jcupitt/libvips) v7.37+
 
-```
+For the sharpest results, please compile libvips from source.
-sudo npm install -g node-gyp
-sudo apt-get install libvips-dev
-```
 
-When installed as a package, please symlink `vips-7.28.pc` (or later, installed with libvips-dev) as `/usr/lib/pkgconfig/vips.pc`. To do this in Ubuntu 13.04 (64-bit), use:
+If you prefer to run a stable, package-managed environment such as Ubuntu 12.04 LTS, [v0.0.3](https://github.com/lovell/sharp/tree/v0.0.3) will work with the libvips-dev package.
-
-	sudo ln -s /usr/lib/x86_64-linux-gnu/pkgconfig/vips-7.28.pc /usr/lib/pkgconfig/vips.pc
 
 ## Install
 
@@ -38,11 +33,9 @@ When installed as a package, please symlink `vips-7.28.pc` (or later, installed
 
 	var sharp = require("sharp");
 
-### crop(inputPath, outputPath, width, height, callback)
+### crop(input, output, width, height, callback)
 
-Scale and crop JPEG `inputPath` to `width` x `height` and write JPEG to `outputPath` calling `callback` when complete.
+Scale and crop to `width` x `height` calling `callback` when complete.
-
-Example:
 
 ```javascript
 sharp.crop("input.jpg", "output.jpg", 300, 200, function(err) {
@@ -54,9 +47,27 @@ sharp.crop("input.jpg", "output.jpg", 300, 200, function(err) {
 });
 ```
 
-### embedWhite(inputPath, outputPath, width, height, callback)
+```javascript
+sharp.crop("input.jpg", sharp.buffer.jpeg, 300, 200, function(err, buffer) {
+  if (err) {
+    throw err;
+  }
+  // buffer contains JPEG image data
+});
+```
 
-Scale and embed JPEG `inputPath` to `width` x `height` using a white canvas and write JPEG to `outputPath` calling `callback` when complete.
+```javascript
+sharp.crop("input.jpg", sharp.buffer.png, 300, 200, function(err, buffer) {
+  if (err) {
+    throw err;
+  }
+  // buffer contains PNG image data (converted from JPEG)
+});
+```
+
+### embedWhite(input, output, width, height, callback)
+
+Scale and embed to `width` x `height` using a white canvas calling `callback` when complete.
 
 ```javascript
 sharp.embedWhite("input.jpg", "output.jpg", 200, 300, function(err) {
@@ -64,54 +75,85 @@ sharp.embedWhite("input.jpg", "output.jpg", 200, 300, function(err) {
     throw err;
   }
   // output.jpg is a 200 pixels wide and 300 pixels high image
-  // containing a scaled version of input.jpg embedded on a white canvas
+  // containing a scaled version of input.png embedded on a white canvas
 });
 ```
 
-### embedBlack(inputPath, outputPath, width, height, callback)
-
-Scale and embed JPEG `inputPath` to `width` x `height` using a black canvas and write JPEG to `outputPath` calling `callback` when complete.
-
 ```javascript
-sharp.embedBlack("input.jpg", "output.jpg", 200, 300, function(err) {
+sharp.embedWhite("input.jpg", sharp.buffer.jpeg, 200, 300, function(err, buffer) {
   if (err) {
     throw err;
   }
-  // output.jpg is a 200 pixels wide and 300 pixels high image
+  // buffer contains JPEG image data
-  // containing a scaled version of input.jpg embedded on a black canvas
 });
 ```
 
+### embedBlack(input, output, width, height, callback)
+
+Scale and embed to `width` x `height` using a black canvas calling `callback` when complete.
+
+```javascript
+sharp.embedBlack("input.png", "output.png", 200, 300, function(err) {
+  if (err) {
+    throw err;
+  }
+  // output.png is a 200 pixels wide and 300 pixels high image
+  // containing a scaled version of input.png embedded on a black canvas
+});
+```
+
+### Parameters common to all methods
+
+#### input
+
+String containing the filename to read from.
+
+#### output
+
+One of:
+* String containing the filename to write to.
+* `sharp.buffer.jpeg` to pass a Buffer containing JPEG image data to `callback`.
+* `sharp.buffer.png` to pass a Buffer containing PNG image data to `callback`.
+
 ## Testing
 
-	npm install --dev sharp
 	npm test
 
 ## Performance
 
-### AMD Athlon 4x core 3.3GHz 512KB L2
+Test environment:
 
-* imagemagick x 5.55 ops/sec ±0.45% (31 runs sampled)
+* AMD Athlon 4 core 3.3GHz 512KB L2 CPU 1333 DDR3
-* gm x 10.31 ops/sec ±3.57% (53 runs sampled)
+* libvips 7.37
-* epeg x 27.79 ops/sec ±0.12% (69 runs sampled)
+* libjpeg-turbo8 1.3.0
-* sharp x 31.52 ops/sec ±8.74% (80 runs sampled)
+* libpng 1.6.6
+* zlib1g 1.2.7
 
-### AWS t1.micro
+#### JPEG
 
-* imagemagick x 1.36 ops/sec ±0.96% (11 runs sampled)
+* imagemagick x 5.53 ops/sec ±0.55% (31 runs sampled)
-* sharp x 12.42 ops/sec ±5.84% (64 runs sampled)
+* gm x 10.86 ops/sec ±0.43% (56 runs sampled)
+* epeg x 28.07 ops/sec ±0.07% (70 runs sampled)
+* sharp-file x 72.01 ops/sec ±7.19% (74 runs sampled)
+* sharp-buffer x 75.73 ops/sec ±0.44% (75 runs sampled)
 
-### AWS m1.medium
+#### PNG
 
-* imagemagick x 1.38 ops/sec ±0.45% (11 runs sampled)
+* imagemagick x 4.65 ops/sec ±0.37% (27 runs sampled)
-* sharp x 12.66 ops/sec ±5.54% (65 runs sampled)
+* gm x 21.65 ops/sec ±0.18% (56 runs sampled)
+* sharp-file x 43.80 ops/sec ±6.81% (75 runs sampled)
+* sharp-buffer x 45.67 ops/sec ±0.41% (75 runs sampled)
 
-### AWS c1.medium
+## Licence
 
-* imagemagick x 2.10 ops/sec ±0.67% (15 runs sampled)
+Copyright 2013, 2014 Lovell Fuller
-* sharp x 18.97 ops/sec ±10.54% (52 runs sampled)
 
-### AWS m3.xlarge
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at [http://www.apache.org/licenses/LICENSE-2.0](http://www.apache.org/licenses/LICENSE-2.0.html)
 
-* imagemagick x 4.46 ops/sec ±0.33% (26 runs sampled)
+Unless required by applicable law or agreed to in writing, software
-* sharp x 28.89 ops/sec ±7.75% (74 runs sampled)
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.

index.js

@@ -1,13 +1,18 @@
 var sharp = require("./build/Release/sharp");
 
+module.exports.buffer = {
+  jpeg: "__jpeg",
+  png: "__png"
+};
+
 module.exports.crop = function(input, output, width, height, callback) {
-  sharp.resize(input, output, width, height, "c", callback)
+  sharp.resize(input, output, width, height, "c", callback);
-}
+};
 
 module.exports.embedWhite = function(input, output, width, height, callback) {
-  sharp.resize(input, output, width, height, "w", callback)
+  sharp.resize(input, output, width, height, "w", callback);
-}
+};
 
 module.exports.embedBlack = function(input, output, width, height, callback) {
-  sharp.resize(input, output, width, height, "b", callback)
+  sharp.resize(input, output, width, height, "b", callback);
-}
+};

package.json

@@ -1,34 +1,37 @@
 {
   "name": "sharp",
-  "version": "0.0.4",
+  "version": "0.0.9",
+  "author": "Lovell Fuller",
+  "description": "High performance module to resize JPEG and PNG images using the libvips image processing library",
+  "scripts": {
+    "test": "node tests/perf.js"
+  },
   "main": "index.js",
-  "description": "High performance Node.js module to resize JPEG images using the libvips image processing library",
   "repository": {
     "type": "git",
     "url": "git://github.com/lovell/sharp"
   },
-  "devDependencies": {
-    "imagemagick": "*",
-    "gm": "*",
-    "epeg": "*",
-    "benchmark": "*"
-  },
-  "scripts": {
-    "test": "node tests/perf.js"
-  },
-  "engines": {
-    "node": ">=0.8"
-  },
   "keywords": [
     "jpeg",
+    "png",
     "resize",
     "thumbnail",
     "sharpen",
     "crop",
     "embed",
     "libvips",
-    "fast"
+    "fast",
+    "buffer"
   ],
-  "author": "Lovell Fuller",
+  "devDependencies": {
-  "license": "Apache 2.0"
+    "imagemagick": "*",
+    "gm": "*",
+    "epeg": "*",
+    "async": "*",
+    "benchmark": "*"
+  },
+  "license": "Apache 2.0",
+  "engines": {
+    "node": ">=0.8"
+  }
 }

src/sharp.cc

@@ -1,80 +1,116 @@
 #include <node.h>
+#include <node_buffer.h>
 #include <math.h>
 #include <string>
-#include <vector>
 #include <vips/vips.h>
 
 using namespace v8;
-
+using namespace node;
-// Free VipsImage children when object goes out of scope
-// Thanks due to https://github.com/dosx/node-vips
-class ImageFreer {
-  public:
-    ImageFreer() {}
-    ~ImageFreer() {
-      for (uint16_t i = 0; i < v_.size(); i++) {
-        if (v_[i] != NULL) {
-          g_object_unref(v_[i]);
-        }
-      }
-      v_.clear();
-    }
-    void add(VipsImage* i) { v_.push_back(i); }
-  private:
-    std::vector<VipsImage*> v_;
-};
 
 struct ResizeBaton {
   std::string src;
   std::string dst;
+  void* buffer_out;
+  size_t buffer_out_len;
   int  cols;
   int  rows;
   bool crop;
   int  embed;
   std::string err;
   Persistent<Function> callback;
+
+  ResizeBaton() : buffer_out_len(0) {}
 };
 
+bool EndsWith(std::string const &str, std::string const &end) {
+  return str.length() >= end.length() && 0 == str.compare(str.length() - end.length(), end.length(), end);
+}
+
+bool IsJpeg(std::string const &str) {
+  return EndsWith(str, ".jpg") || EndsWith(str, ".jpeg");
+}
+
+bool IsPng(std::string const &str) {
+  return EndsWith(str, ".png");
+}
+
 void ResizeAsync(uv_work_t *work) {
   ResizeBaton* baton = static_cast<ResizeBaton*>(work->data);
 
-  VipsImage *in = vips_image_new_mode((baton->src).c_str(), "p");
+  VipsImage *in = vips_image_new();
-  vips_jpegload((baton->src).c_str(), &in, NULL);
+  if (IsJpeg(baton->src)) {
+    vips_jpegload((baton->src).c_str(), &in, NULL);
+  } else if (IsPng(baton->src)) {
+    vips_pngload((baton->src).c_str(), &in, NULL);
+  } else {
+    (baton->err).append("Unsupported input file type");
+    return;
+  }
   if (in == NULL) {
     (baton->err).append(vips_error_buffer());
     vips_error_clear();
     return;
   }
-  ImageFreer freer;
-  freer.add(in);
 
-  VipsImage* img = in;
+  double xfactor = static_cast<double>(in->Xsize) / std::max(baton->cols, 1);
-  VipsImage* t[4];
+  double yfactor = static_cast<double>(in->Ysize) / std::max(baton->rows, 1);
-
-  if (im_open_local_array(img, t, 4, "temp", "p")) {
-    (baton->err).append(vips_error_buffer());
-    vips_error_clear();
-    return;
-  }
-
-  double xfactor = static_cast<double>(img->Xsize) / std::max(baton->cols, 1);
-  double yfactor = static_cast<double>(img->Ysize) / std::max(baton->rows, 1);
   double factor = baton->crop ? std::min(xfactor, yfactor) : std::max(xfactor, yfactor);
   factor = std::max(factor, 1.0);
   int shrink = floor(factor);
   double residual = shrink / factor;
 
-  // Use im_shrink with the integral reduction
+  // Try to use libjpeg shrink-on-load
-  if (im_shrink(img, t[0], shrink, shrink)) {
+  int shrink_on_load = 1;
+  if (IsJpeg(baton->src)) {
+    if (shrink >= 8) {
+      residual = residual * shrink / 8;
+      shrink_on_load = 8;
+      shrink = 1;
+    } else if (shrink >= 4) {
+      residual = residual * shrink / 4;
+      shrink_on_load = 4;
+      shrink = 1;
+    } else if (shrink >= 2) {
+      residual = residual * shrink / 2;
+      shrink_on_load = 2;
+      shrink = 1;
+    }
+    if (shrink_on_load > 1) {
+      if (vips_jpegload((baton->src).c_str(), &in, "shrink", shrink_on_load, NULL)) {
+        (baton->err).append(vips_error_buffer());
+        vips_error_clear();
+        g_object_unref(in);
+        return;
+      }
+    }
+  }
+
+  VipsImage* img = in;
+  VipsImage* t[4];
+  if (im_open_local_array(img, t, 4, "temp", "p")) {
     (baton->err).append(vips_error_buffer());
     vips_error_clear();
+    g_object_unref(in);
     return;
   }
 
-  // Use im_affinei with the remaining float part using bilinear interpolation
+  if (shrink > 1) {
-  if (im_affinei_all(t[0], t[1], vips_interpolate_bilinear_static(), residual, 0, 0, residual, 0, 0)) {
+    // Use vips_shrink with the integral reduction
+    if (vips_shrink(img, &t[0], shrink, shrink, NULL)) {
+      (baton->err).append(vips_error_buffer());
+      vips_error_clear();
+      g_object_unref(in);
+      return;
+    }
+  } else {
+    t[0] = img;
+  }
+
+  // Use vips_affine with the remaining float part using bilinear interpolation
+  if (vips_affine(t[0], &t[1], residual, 0, 0, residual, "interpolate", vips_interpolate_bilinear_static(), NULL)) {
     (baton->err).append(vips_error_buffer());
     vips_error_clear();
+    g_object_unref(in);
     return;
   }
   img = t[1];
@@ -87,6 +123,7 @@ void ResizeAsync(uv_work_t *work) {
     if (im_extract_area(img, t[2], left, top, width, height)) {
       (baton->err).append(vips_error_buffer());
       vips_error_clear();
+      g_object_unref(in);
       return;
     }
     img = t[2];
@@ -96,6 +133,7 @@ void ResizeAsync(uv_work_t *work) {
     if (im_embed(img, t[2], baton->embed, left, top, baton->cols, baton->rows)) {
       (baton->err).append(vips_error_buffer());
       vips_error_clear();
+      g_object_unref(in);
       return;
     }
     img = t[2];
@@ -110,14 +148,40 @@ void ResizeAsync(uv_work_t *work) {
   if (im_conv(img, t[3], sharpen)) { 
     (baton->err).append(vips_error_buffer());
     vips_error_clear();
+    g_object_unref(in);
     return;
   }
   img = t[3];
 
-  if (vips_jpegsave(img, baton->dst.c_str(), "Q", 80, "profile", "none", "optimize_coding", TRUE, NULL)) {
+  if (baton->dst == "__jpeg") {
-    (baton->err).append(vips_error_buffer());
+    // Write JPEG to buffer
-    vips_error_clear();
+    if (vips_jpegsave_buffer(img, &baton->buffer_out, &baton->buffer_out_len, "strip", TRUE, "Q", 80, "optimize_coding", TRUE, NULL)) {
+      (baton->err).append(vips_error_buffer());
+      vips_error_clear();
+    }
+  } else if (baton->dst == "__png") {
+    // Write PNG to buffer
+    if (vips_pngsave_buffer(img, &baton->buffer_out, &baton->buffer_out_len, "strip", TRUE, "compression", 6, "interlace", FALSE, NULL)) {
+      (baton->err).append(vips_error_buffer());
+      vips_error_clear();
+    }
+  } else if (EndsWith(baton->dst, ".jpg") || EndsWith(baton->dst, ".jpeg"))  {
+    // Write JPEG to file
+    if (vips_foreign_save(img, baton->dst.c_str(), "strip", TRUE, "Q", 80, "optimize_coding", TRUE, NULL)) {
+      (baton->err).append(vips_error_buffer());
+      vips_error_clear();
+    }
+  } else if (EndsWith(baton->dst, ".png")) {
+    // Write PNG to file
+    if (vips_foreign_save(img, baton->dst.c_str(), "strip", TRUE, "compression", 6, "interlace", FALSE, NULL)) {
+      (baton->err).append(vips_error_buffer());
+      vips_error_clear();
+    }
+  } else {
+    (baton->err).append("Unsupported output file type");
   }
+  g_object_unref(in);
+  vips_thread_shutdown();
 }
 
 void ResizeAsyncAfter(uv_work_t *work, int status) {
@@ -125,14 +189,19 @@ void ResizeAsyncAfter(uv_work_t *work, int status) {
 
   ResizeBaton *baton = static_cast<ResizeBaton*>(work->data);
 
-  Local<Value> argv[1];
+  Local<Value> null = Local<Value>::New(Null());
+  Local<Value> argv[2] = {null, null};
   if (!baton->err.empty()) {
+    // Error
     argv[0] = String::New(baton->err.data(), baton->err.size());
-  } else {
+  } else if (baton->buffer_out_len > 0) {
-    argv[0] = Local<Value>::New(Null());
+    // Buffer
+    Buffer *buffer = Buffer::New((const char*)(baton->buffer_out), baton->buffer_out_len);
+    argv[1] = Local<Object>::New(buffer->handle_);
+    vips_free(baton->buffer_out);
   }
 
-  baton->callback->Call(Context::GetCurrent()->Global(), 1, argv);
+  baton->callback->Call(Context::GetCurrent()->Global(), 2, argv);
   baton->callback.Dispose();
   delete baton;
   delete work;
@@ -148,7 +217,7 @@ Handle<Value> Resize(const Arguments& args) {
   baton->rows = args[3]->Int32Value();
   Local<String> canvas = args[4]->ToString();
   if (canvas->Equals(String::NewSymbol("c"))) {
-	baton->crop = true;
+    baton->crop = true;
   } else if (canvas->Equals(String::NewSymbol("w"))) {
     baton->crop = false;
     baton->embed = 4;
@@ -164,10 +233,16 @@ Handle<Value> Resize(const Arguments& args) {
   return Undefined();
 }
 
+static void at_exit(void* arg) {
+  HandleScope scope;
+  vips_shutdown();
+}
+
 extern "C" void init(Handle<Object> target) {
   HandleScope scope;
   vips_init("");
+  AtExit(at_exit);
   NODE_SET_METHOD(target, "resize", Resize);
 };
 
-NODE_MODULE(sharp, init)
+NODE_MODULE(sharp, init);

tests/perf.js

@@ -2,63 +2,145 @@ var sharp = require("../index");
 var imagemagick = require("imagemagick");
 var gm = require("gm");
 var epeg = require("epeg");
+var async = require("async");
 var assert = require("assert");
 var Benchmark = require("benchmark");
 
-var input = __dirname + "/2569067123_aca715a2ee_o.jpg"; // http://www.flickr.com/photos/grizdave/2569067123/
+var inputJpg = __dirname + "/2569067123_aca715a2ee_o.jpg"; // http://www.flickr.com/photos/grizdave/2569067123/
-var output = __dirname + "/output.jpg";
+var outputJpg = __dirname + "/output.jpg";
+
+var inputPng = __dirname + "/50020484-00001.png"; // http://c.searspartsdirect.com/lis_png/PLDM/50020484-00001.png
+var outputPng = __dirname + "/output.png";
+
 var width = 640;
 var height = 480;
 
-var suite = new Benchmark.Suite;
+async.series({
-suite.add("imagemagick", {
+  jpeg: function(callback) {
-  "defer": true,
+    (new Benchmark.Suite("jpeg")).add("imagemagick", {
-  "fn": function(deferred) {
+      defer: true,
-    imagemagick.resize({
+      fn: function(deferred) {
-      srcPath: input,
+        imagemagick.resize({
-      dstPath: output,
+          srcPath: inputJpg,
-      quality: 0.75,
+          dstPath: outputJpg,
-      width: width,
+          quality: 0.8,
-      height: height
+          width: width,
-    }, function(err) {
+          height: height
-      if (err) {
+        }, function(err) {
-        throw err;
+          if (err) {
-      } else {
+            throw err;
+          } else {
+            deferred.resolve();
+          }
+        });
+      }
+    }).add("gm", {
+      defer: true,
+      fn: function(deferred) {
+        gm(inputJpg).crop(width, height).quality(80).write(outputJpg, function (err) {
+          if (err) {
+            throw err;
+          } else {
+            deferred.resolve();
+          }
+        });
+      }
+    }).add("epeg", {
+      defer: true,
+      fn: function(deferred) {
+        var image = new epeg.Image({path: inputJpg});
+        image.downsize(width, height, 80).saveTo(outputJpg);
         deferred.resolve();
       }
-    });
+    }).add("sharp-file", {
-  }
+      defer: true,
-}).add("gm", {
+      fn: function(deferred) {
-  "defer": true,
+        sharp.crop(inputJpg, outputJpg, width, height, function(err) {
-  "fn": function(deferred) {
+          if (err) {
-    gm(input).crop(width, height).write(output, function (err) {
+            throw err;
-      if (err) {
+          } else {
-        throw err;
+            deferred.resolve();
-      } else {
+          }
-        deferred.resolve();
+        });
       }
-    });
+    }).add("sharp-buffer", {
-  }
+      defer: true,
-}).add("epeg", {
+      fn: function(deferred) {
-  "defer": true,
+        sharp.crop(inputJpg, sharp.buffer.jpeg, width, height, function(err, buffer) {
-  "fn": function(deferred) {
+          if (err) {
-    var image = new epeg.Image({path: input});
+            throw err;
-    image.downsize(width, height).saveTo(output);
+          } else {
-    deferred.resolve();
+            assert.notStrictEqual(null, buffer);
-  }
+            deferred.resolve();
-}).add("sharp", {
+          }
-  "defer": true,
+        });
-  "fn": function(deferred) {
-    sharp.crop(input, output, width, height, function(err) {
-      if (err) {
-        throw err;
-      } else {
-        deferred.resolve();
       }
-    });
+    }).on("cycle", function(event) {
+      console.log("jpeg " + String(event.target));
+    }).on("complete", function() {
+      callback(null, this.filter("fastest").pluck("name"));
+    }).run();
+  },
+  png: function(callback) {
+    (new Benchmark.Suite("png")).add("imagemagick", {
+      defer: true,
+      fn: function(deferred) {
+        imagemagick.resize({
+          srcPath: inputPng,
+          dstPath: outputPng,
+          width: width,
+          height: height
+        }, function(err) {
+          if (err) {
+            throw err;
+          } else {
+            deferred.resolve();
+          }
+        });
+      }
+    }).add("gm", {
+      defer: true,
+      fn: function(deferred) {
+        gm(inputPng).crop(width, height).write(outputPng, function (err) {
+          if (err) {
+            throw err;
+          } else {
+            deferred.resolve();
+          }
+        });
+      }
+    }).add("sharp-file", {
+      defer: true,
+      fn: function(deferred) {
+        sharp.crop(inputPng, outputPng, width, height, function(err) {
+          if (err) {
+            throw err;
+          } else {
+            deferred.resolve();
+          }
+        });
+      }
+    }).add("sharp-buffer", {
+      defer: true,
+      fn: function(deferred) {
+        sharp.crop(inputPng, sharp.buffer.png, width, height, function(err, buffer) {
+          if (err) {
+            throw err;
+          } else {
+            assert.notStrictEqual(null, buffer);
+            deferred.resolve();
+          }
+        });
+      }
+    }).on("cycle", function(event) {
+      console.log(" png " + String(event.target));
+    }).on("complete", function() {
+      callback(null, this.filter("fastest").pluck("name"));
+    }).run();
   }
-}).on("cycle", function(event) {
+}, function(err, results) {
-  console.log(String(event.target));
+  assert(!err, err);
-}).on("complete", function() {
+  Object.keys(results).forEach(function(format) {
-  assert(this.filter("fastest").pluck("name") == "sharp");
+    assert.strictEqual("sharp", results[format].toString().substr(0, 5), "sharp was slower than " + results[format] + " for " + format);
-}).run();
+  });
+});