diff --git a/.gitignore b/.gitignore
index f0e8ed9c..75b47ca5 100644
--- a/.gitignore
+++ b/.gitignore
@@ -2,7 +2,7 @@ build
 node_modules
 coverage
 test/bench/node_modules
-test/fixtures/output.*
+test/fixtures/output*
 test/leak/libvips.supp
 
 # Mac OS X
diff --git a/README.md b/README.md
index c9ff0211..aaa78888 100755
--- a/README.md
+++ b/README.md
@@ -12,7 +12,11 @@
 The typical use case for this high speed Node.js module is to convert large images of many formats to smaller, web-friendly JPEG, PNG and WebP images of varying dimensions.
 
 This module supports reading and writing JPEG, PNG and WebP images to and from Streams, Buffer objects and the filesystem.
-It also supports reading images of many other types from the filesystem via libmagick, libgraphicsmagick or [OpenSlide](http://openslide.org/) if present and writing Deep Zoom images.
+It also supports reading images of many other formats from the filesystem via libmagick, libgraphicsmagick or [OpenSlide](http://openslide.org/) if present.
+
+Deep Zoom image pyramids can be generated, suitable for use with "slippy map" tile viewers like
+[OpenSeadragon](https://github.com/openseadragon/openseadragon) and [Leaflet](https://github.com/turban/Leaflet.Zoomify).
+
 Colour spaces, embedded ICC profiles and alpha transparency channels are all handled correctly.
 
 Only small regions of uncompressed image data are held in memory and processed at a time, taking full advantage of multiple CPU cores and L1/L2/L3 cache. Resizing an image is typically 4x faster than using the quickest ImageMagick and GraphicsMagick settings.
@@ -498,6 +502,13 @@ Include all metadata (EXIF, XMP, IPTC) from the input image in the output image.
 
 The default behaviour is to strip all metadata and convert to the device-independent sRGB colour space.
 
+#### tile([size], [overlap])
+
+The size and overlap, in pixels, of square Deep Zoom image pyramid tiles.
+
+* `size` is an integral Number between 1 and 8192. The default value is 256 pixels.
+* `overlap` is an integral Number between 0 and 8192. The default value is 0 pixels.
+
 #### withoutChromaSubsampling()
 
 Disable the use of [chroma subsampling](http://en.wikipedia.org/wiki/Chroma_subsampling) with JPEG output (4:4:4).
@@ -519,12 +530,6 @@ _Requires libvips 7.42.0+_
 
 An advanced setting to disable adaptive row filtering for the lossless PNG output format.
 
-#### tileSize(tileSize)
-Setting the tile_size when DZI output format is selected. Default is 256.
-
-#### tileOverlap(tileOverlap)
-Setting the overlap when DZI output format is selected. Default is 0.
-
 ### Output methods
 
 #### toFile(filename, [callback])
diff --git a/index.js b/index.js
index d83b00f6..631d8c1f 100755
--- a/index.js
+++ b/index.js
@@ -380,28 +380,28 @@ Sharp.prototype.withMetadata = function(withMetadata) {
 };
 
 /*
-  dz tile size for DZ output
-  max is 8192 since 7.36.5 (1024 before)
+  Tile size and overlap for Deep Zoom output
 */
-Sharp.prototype.tileSize = function(tileSize) {
-  if (!Number.isNaN(tileSize) && tileSize >= 1 && tileSize <= 8192) {
-    this.options.tileSize = tileSize;
-  } else {
-    throw new Error('Invalid tileSize (1 to 8192) ' + tileSize);
+Sharp.prototype.tile = function(size, overlap) {
+  // Size of square tiles, in pixels
+  if (typeof size !== 'undefined' && size !== null) {
+    if (!Number.isNaN(size) && size % 1 === 0 && size >= 1 && size <= 8192) {
+      this.options.tileSize = size;
+    } else {
+      throw new Error('Invalid tile size (1 to 8192) ' + size);
+    }
   }
-  return this;
-};
-
-/*
-  dz overlap for DZ output
-*/
-Sharp.prototype.tileOverlap = function(tileOverlap) {
-  if (!Number.isNaN(tileOverlap) && tileOverlap >=0 && tileOverlap <= 8192) {
-    this.options.tileOverlap = tileOverlap;
-  } else {
-    throw new Error('Invalid tileOverlap (0 to 8192) ' + tileOverlap);
+  // Overlap of tiles, in pixels
+  if (typeof overlap !== 'undefined' && overlap !== null) {
+    if (!Number.isNaN(overlap) && overlap % 1 === 0 && overlap >=0 && overlap <= 8192) {
+      if (overlap > this.options.tileSize) {
+        throw new Error('Tile overlap ' + overlap + ' cannot be larger than tile size ' + this.options.tileSize);
+      }
+      this.options.tileOverlap = overlap;
+    } else {
+      throw new Error('Invalid tile overlap (0 to 8192) ' + overlap);
+    }
   }
-
   return this;
 };
 
@@ -511,14 +511,6 @@ Sharp.prototype.raw = function() {
   return this;
 };
 
-/*
-  Force DZI output
-*/
-Sharp.prototype.dz = function() {
-  this.options.output = '__dzi';
-  return this;
-};
-
 /*
   Force output to a given format
   @param format is either the id as a String or an Object with an 'id' attribute
diff --git a/package.json b/package.json
old mode 100644
new mode 100755
index dc4cbb71..2caa02c2
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "sharp",
-  "version": "0.9.3",
+  "version": "0.10.0",
   "author": "Lovell Fuller <npm@lovell.info>",
   "contributors": [
     "Pierre Inglebert <pierre.inglebert@gmail.com>",
@@ -30,6 +30,7 @@
     "png",
     "webp",
     "tiff",
+    "dzi",
     "resize",
     "thumbnail",
     "crop",
@@ -37,17 +38,19 @@
     "vips"
   ],
   "dependencies": {
-    "bluebird": "^2.9.12",
-    "color": "^0.7.3",
+    "bluebird": "^2.9.14",
+    "color": "^0.8.0",
     "nan": "^1.6.2",
     "semver": "^4.3.1"
   },
   "devDependencies": {
     "mocha": "^2.1.0",
-    "mocha-jshint": "^0.0.9",
+    "mocha-jshint": "^1.0.0",
     "istanbul": "^0.3.6",
     "coveralls": "^2.11.2",
-    "node-cpplint": "^0.4.0"
+    "node-cpplint": "^0.4.0",
+    "rimraf": "^2.3.2",
+    "async": "^0.9.0"
   },
   "license": "Apache 2.0",
   "engines": {
diff --git a/src/common.cc b/src/common.cc
index 0f6c345c..e48e8b06 100755
--- a/src/common.cc
+++ b/src/common.cc
@@ -37,96 +37,61 @@ namespace sharp {
   */
   ImageType DetermineImageType(void *buffer, size_t const length) {
     ImageType imageType = ImageType::UNKNOWN;
-#if (VIPS_MAJOR_VERSION >= 8)
-    if (vips_foreign_is_a_buffer("jpegload_buffer", buffer, length)) {
-      imageType = ImageType::JPEG;
-    } else if (vips_foreign_is_a_buffer("pngload_buffer", buffer, length)) {
-      imageType = ImageType::PNG;
-    } else if (vips_foreign_is_a_buffer("webpload_buffer", buffer, length)) {
-      imageType = ImageType::WEBP;
-    } else if (vips_foreign_is_a_buffer("tiffload_buffer", buffer, length)) {
-      imageType = ImageType::TIFF;
-    } else if(vips_foreign_is_a_buffer("magickload_buffer", buffer, length)) {
-      imageType = ImageType::MAGICK;
-    }
-#else
-    const char* loader = vips_foreign_find_load_buffer(buffer, length);
-
-    if (loader != NULL) {
-      if (!strcmp(loader, "VipsForeignLoadJpegBuffer")) {
+    char const *load = vips_foreign_find_load_buffer(buffer, length);
+    if (load != NULL) {
+      std::string loader = load;
+      if (EndsWith(loader, "JpegBuffer")) {
         imageType = ImageType::JPEG;
-      } else if (!strcmp(loader, "VipsForeignLoadPngBuffer")) {
+      } else if (EndsWith(loader, "PngBuffer")) {
         imageType = ImageType::PNG;
-      } else if (!strcmp(loader, "VipsForeignLoadWebpBuffer")) {
+      } else if (EndsWith(loader, "WebpBuffer")) {
         imageType = ImageType::WEBP;
-      } else if (!strcmp(loader, "VipsForeignLoadTiffBuffer")) {
+      } else if (EndsWith(loader, "TiffBuffer")) {
         imageType = ImageType::TIFF;
-      } else if (!strcmp(loader, "VipsForeignLoadMagickBuffer")) {
+      } else if (EndsWith(loader, "MagickBuffer")) {
         imageType = ImageType::MAGICK;
       }
     }
-#endif
     return imageType;
   }
 
   /*
     Initialise and return a VipsImage from a buffer. Supports JPEG, PNG, WebP and TIFF.
   */
-  VipsImage* InitImage(ImageType imageType, void *buffer, size_t const length, VipsAccess const access) {
-    VipsImage *image = NULL;
-    if (imageType == ImageType::JPEG) {
-      vips_jpegload_buffer(buffer, length, &image, "access", access, NULL);
-    } else if (imageType == ImageType::PNG) {
-      vips_pngload_buffer(buffer, length, &image, "access", access, NULL);
-    } else if (imageType == ImageType::WEBP) {
-      vips_webpload_buffer(buffer, length, &image, "access", access, NULL);
-    } else if (imageType == ImageType::TIFF) {
-      vips_tiffload_buffer(buffer, length, &image, "access", access, NULL);
-#if (VIPS_MAJOR_VERSION >= 8)
-    } else if (imageType == ImageType::MAGICK) {
-      vips_magickload_buffer(buffer, length, &image, "access", access, NULL);
-#endif
-    }
-    return image;
+  VipsImage* InitImage(void *buffer, size_t const length, VipsAccess const access) {
+    return vips_image_new_from_buffer(buffer, length, NULL, "access", access, NULL);
   }
 
   /*
-    Inpect the first 2-4 bytes of a file to determine image format
+    Determine image format, reads the first few bytes of the file
   */
   ImageType DetermineImageType(char const *file) {
     ImageType imageType = ImageType::UNKNOWN;
-    if (vips_foreign_is_a("jpegload", file)) {
-      imageType = ImageType::JPEG;
-    } else if (vips_foreign_is_a("pngload", file)) {
-      imageType = ImageType::PNG;
-    } else if (vips_foreign_is_a("webpload", file)) {
-      imageType = ImageType::WEBP;
-    } else if (vips_foreign_is_a("tiffload", file)) {
-      imageType = ImageType::TIFF;
-    } else if(vips_foreign_is_a("magickload", file)) {
-      imageType = ImageType::MAGICK;
+    char const *load = vips_foreign_find_load(file);
+    if (load != NULL) {
+      std::string loader = load;
+      if (EndsWith(loader, "JpegFile")) {
+        imageType = ImageType::JPEG;
+      } else if (EndsWith(loader, "Png")) {
+        imageType = ImageType::PNG;
+      } else if (EndsWith(loader, "WebpFile")) {
+        imageType = ImageType::WEBP;
+      } else if (EndsWith(loader, "Openslide")) {
+        imageType = ImageType::OPENSLIDE;
+      } else if (EndsWith(loader, "TiffFile")) {
+        imageType = ImageType::TIFF;
+      } else if (EndsWith(loader, "MagickFile")) {
+        imageType = ImageType::MAGICK;
+      }
     }
-
     return imageType;
   }
 
   /*
     Initialise and return a VipsImage from a file.
   */
-  VipsImage* InitImage(ImageType imageType, char const *file, VipsAccess const access) {
-    VipsImage *image = NULL;
-    if (imageType == ImageType::JPEG) {
-      vips_jpegload(file, &image, "access", access, NULL);
-    } else if (imageType == ImageType::PNG) {
-      vips_pngload(file, &image, "access", access, NULL);
-    } else if (imageType == ImageType::WEBP) {
-      vips_webpload(file, &image, "access", access, NULL);
-    } else if (imageType == ImageType::TIFF) {
-      vips_tiffload(file, &image, "access", access, NULL);
-    } else if (imageType == ImageType::MAGICK) {
-      vips_magickload(file, &image, "access", access, NULL);
-    }
-    return image;
+  VipsImage* InitImage(char const *file, VipsAccess const access) {
+    return vips_image_new_from_file(file, "access", access, NULL);
   }
 
   /*
diff --git a/src/common.h b/src/common.h
index 0712ef15..f27e36df 100755
--- a/src/common.h
+++ b/src/common.h
@@ -10,7 +10,7 @@ namespace sharp {
     WEBP,
     TIFF,
     MAGICK,
-    DZ
+    OPENSLIDE
   };
 
   // How many tasks are in the queue?
@@ -39,12 +39,12 @@ namespace sharp {
   /*
     Initialise and return a VipsImage from a buffer. Supports JPEG, PNG, WebP and TIFF.
   */
-  VipsImage* InitImage(ImageType imageType, void *buffer, size_t const length, VipsAccess const access);
+  VipsImage* InitImage(void *buffer, size_t const length, VipsAccess const access);
 
   /*
     Initialise and return a VipsImage from a file.
   */
-  VipsImage* InitImage(ImageType imageType, char const *file, VipsAccess const access);
+  VipsImage* InitImage(char const *file, VipsAccess const access);
 
   /*
     Does this image have an embedded profile?
diff --git a/src/metadata.cc b/src/metadata.cc
index 20473058..a8ceab42 100755
--- a/src/metadata.cc
+++ b/src/metadata.cc
@@ -61,7 +61,7 @@ class MetadataWorker : public NanAsyncWorker {
       // From buffer
       imageType = DetermineImageType(baton->bufferIn, baton->bufferInLength);
       if (imageType != ImageType::UNKNOWN) {
-        image = InitImage(imageType, baton->bufferIn, baton->bufferInLength, VIPS_ACCESS_RANDOM);
+        image = InitImage(baton->bufferIn, baton->bufferInLength, VIPS_ACCESS_RANDOM);
         if (image == NULL) {
           (baton->err).append("Input buffer has corrupt header");
           imageType = ImageType::UNKNOWN;
@@ -73,7 +73,7 @@ class MetadataWorker : public NanAsyncWorker {
       // From file
       imageType = DetermineImageType(baton->fileIn.c_str());
       if (imageType != ImageType::UNKNOWN) {
-        image = InitImage(imageType, baton->fileIn.c_str(), VIPS_ACCESS_RANDOM);
+        image = InitImage(baton->fileIn.c_str(), VIPS_ACCESS_RANDOM);
         if (image == NULL) {
           (baton->err).append("Input file has corrupt header");
           imageType = ImageType::UNKNOWN;
@@ -90,7 +90,7 @@ class MetadataWorker : public NanAsyncWorker {
         case ImageType::WEBP: baton->format = "webp"; break;
         case ImageType::TIFF: baton->format = "tiff"; break;
         case ImageType::MAGICK: baton->format = "magick"; break;
-        case ImageType::DZ: baton->format = "dzi"; break;
+        case ImageType::OPENSLIDE: baton->format = "openslide"; break;
         case ImageType::UNKNOWN: break;
       }
       // VipsImage attributes
diff --git a/src/resize.cc b/src/resize.cc
index b37eeaca..ffcd3e85 100755
--- a/src/resize.cc
+++ b/src/resize.cc
@@ -172,7 +172,7 @@ class ResizeWorker : public NanAsyncWorker {
       // From buffer
       inputImageType = DetermineImageType(baton->bufferIn, baton->bufferInLength);
       if (inputImageType != ImageType::UNKNOWN) {
-        image = InitImage(inputImageType, baton->bufferIn, baton->bufferInLength, baton->accessMethod);
+        image = InitImage(baton->bufferIn, baton->bufferInLength, baton->accessMethod);
         if (image != NULL) {
           // Listen for "postclose" signal to delete input buffer
           g_signal_connect(image, "postclose", G_CALLBACK(DeleteBuffer), baton->bufferIn);
@@ -190,7 +190,7 @@ class ResizeWorker : public NanAsyncWorker {
       // From file
       inputImageType = DetermineImageType(baton->fileIn.c_str());
       if (inputImageType != ImageType::UNKNOWN) {
-        image = InitImage(inputImageType, baton->fileIn.c_str(), baton->accessMethod);
+        image = InitImage(baton->fileIn.c_str(), baton->accessMethod);
         if (image == NULL) {
           (baton->err).append("Input file has corrupt header");
           inputImageType = ImageType::UNKNOWN;
@@ -801,7 +801,7 @@ class ResizeWorker : public NanAsyncWorker {
           return Error(baton, hook);
         }
         baton->outputFormat = "tiff";
-      } else if (outputDz || matchInput) {
+      } else if (outputDz) {
         // Write DZ to file
         std::string filename_no_extension = baton->output.substr(0, baton->output.length() - 4);
         if (vips_dzsave(image, filename_no_extension.c_str(), "strip", !baton->withMetadata,
@@ -845,11 +845,6 @@ class ResizeWorker : public NanAsyncWorker {
       info->Set(NanNew<String>("width"), NanNew<Uint32>(static_cast<uint32_t>(width)));
       info->Set(NanNew<String>("height"), NanNew<Uint32>(static_cast<uint32_t>(height)));
 
-      if (baton->outputFormat == "dz" ) {
-        info->Set(NanNew<String>("tileSize"), NanNew<Uint32>(static_cast<uint32_t>(baton->tileSize)));
-        info->Set(NanNew<String>("tileOverlap"), NanNew<Uint32>(static_cast<uint32_t>(baton->tileOverlap)));
-      }
-
       if (baton->bufferOutLength > 0) {
         // Copy data to new Buffer
         argv[1] = NanNewBufferHandle(static_cast<char*>(baton->bufferOut), baton->bufferOutLength);
diff --git a/test/unit/io.js b/test/unit/io.js
index 4b490161..fd1cb20a 100755
--- a/test/unit/io.js
+++ b/test/unit/io.js
@@ -519,42 +519,6 @@ describe('Input/output', function() {
     });
   }
 
-  if (sharp.format.dz.output.file) {
-    it('Convert JPEG to DZ', function(done) {
-      sharp(fixtures.inputJpg)
-        .resize(320, 240)
-        .toFormat(sharp.format.dz)
-        .toFile(fixtures.path('output.jpg.dzi'), function(err, info) {
-          if (err) throw err;
-          assert.strictEqual(true, info.size > 0);
-          assert.strictEqual('dz', info.format);
-          assert.strictEqual(320, info.width);
-          assert.strictEqual(240, info.height);
-          assert.strictEqual(256, info.tileSize);
-          assert.strictEqual(0, info.tileOverlap);
-          done();
-        });
-    });
-
-    it('Convert JPEG to DZ (test tileSize and tileOverlap)', function(done) {
-      sharp(fixtures.inputJpg)
-        .resize(320, 240)
-        .toFormat(sharp.format.dz)
-        .tileSize(512)
-        .tileOverlap(10)
-        .toFile(fixtures.path('output.tileTest.jpg.dzi'), function(err, info) {
-          if (err) throw err;
-          assert.strictEqual(true, info.size > 0);
-          assert.strictEqual('dz', info.format);
-          assert.strictEqual(320, info.width);
-          assert.strictEqual(240, info.height);
-          assert.strictEqual(512, info.tileSize);
-          assert.strictEqual(10, info.tileOverlap);
-          done();
-        });
-    });
-}
-
   if (sharp.format.tiff.input.buffer) {
     it('Load TIFF from Buffer', function(done) {
       var inputTiffBuffer = fs.readFileSync(fixtures.inputTiff);
@@ -591,6 +555,22 @@ describe('Input/output', function() {
     });
   }
 
+  if (sharp.format.openslide.input.file) {
+    it('Load Aperio SVS file via Openslide', function(done) {
+      sharp(fixtures.inputSvs)
+        .resize(320, 240)
+        .jpeg()
+        .toBuffer(function(err, data, info) {
+          if (err) throw err;
+          assert.strictEqual(true, data.length > 0);
+          assert.strictEqual('jpeg', info.format);
+          assert.strictEqual(320, info.width);
+          assert.strictEqual(240, info.height);
+          done();
+        });
+    });
+  }
+
   if (sharp.format.raw.output.buffer) {
     describe('Ouput raw, uncompressed image data', function() {
       it('1 channel greyscale image', function(done) {
@@ -704,65 +684,4 @@ describe('Input/output', function() {
 
   });
 
-  if(sharp.format.openslide.input.file) {
-    describe('Openslide output', function() {
-        it('Aperio - convert SVS to PNG', function(done) {
-        sharp(fixtures.inputSvs)
-          .toFile(fixtures.path('output.svs.png'), function(err, info) {
-            if (err) throw err;
-            assert.strictEqual(true, info.size > 0);
-            assert.strictEqual('png', info.format);
-            assert.strictEqual(2220, info.width);
-            assert.strictEqual(2967, info.height);
-            done();
-          });
-        });
-        it('Aperio - convert SVS to JPEG', function(done) {
-        sharp(fixtures.inputSvs)
-          .toFile(fixtures.path('output.svs.jpeg'), function(err, info) {
-            if (err) throw err;
-            assert.strictEqual(true, info.size > 0);
-            assert.strictEqual('jpeg', info.format);
-            assert.strictEqual(2220, info.width);
-            assert.strictEqual(2967, info.height);
-            done();
-          });
-        });
-        it('Aperio - convert SVS to TIFF', function(done) {
-        sharp(fixtures.inputSvs)
-          .toFile(fixtures.path('output.svs.tiff'), function(err, info) {
-            if (err) throw err;
-            assert.strictEqual(true, info.size > 0);
-            assert.strictEqual('tiff', info.format);
-            assert.strictEqual(2220, info.width);
-            assert.strictEqual(2967, info.height);
-            done();
-          });
-        });
-        it('Aperio - convert SVS to WEBP', function(done) {
-        sharp(fixtures.inputSvs)
-          .toFile(fixtures.path('output.svs.webp'), function(err, info) {
-            if (err) throw err;
-            assert.strictEqual(true, info.size > 0);
-            assert.strictEqual('webp', info.format);
-            assert.strictEqual(2220, info.width);
-            assert.strictEqual(2967, info.height);
-            done();
-          });
-        });
-        it('Aperio - convert SVS to DZI', function(done) {
-        sharp(fixtures.inputSvs)
-          .toFile(fixtures.path('output.aperio.svs.dzi'), function(err, info) {
-            if (err) throw err;
-            assert.strictEqual(true, info.size > 0);
-            assert.strictEqual('dz', info.format);
-            assert.strictEqual(2220, info.width);
-            assert.strictEqual(2967, info.height);
-            assert.strictEqual(256, info.tileSize);
-            assert.strictEqual(0, info.tileOverlap);
-            done();
-          });
-        });
-    });
-  }
 });
diff --git a/test/unit/metadata.js b/test/unit/metadata.js
index 272e9162..6ea7e11d 100755
--- a/test/unit/metadata.js
+++ b/test/unit/metadata.js
@@ -109,6 +109,22 @@ describe('Image metadata', function() {
     });
   });
 
+  if (sharp.format.openslide.input.file) {
+    it('Aperio SVS via openslide', function(done) {
+      sharp(fixtures.inputSvs).metadata(function(err, metadata) {
+        if (err) throw err;
+        assert.strictEqual('openslide', metadata.format);
+        assert.strictEqual(2220, metadata.width);
+        assert.strictEqual(2967, metadata.height);
+        assert.strictEqual(4, metadata.channels);
+        assert.strictEqual('rgb', metadata.space);
+        assert.strictEqual(false, metadata.hasProfile);
+        assert.strictEqual(true, metadata.hasAlpha);
+        done();
+      });
+    });
+  }
+
   it('File in, Promise out', function(done) {
     sharp(fixtures.inputJpg).metadata().then(function(metadata) {
       assert.strictEqual('jpeg', metadata.format);
diff --git a/test/unit/tile.js b/test/unit/tile.js
new file mode 100755
index 00000000..f109ba7a
--- /dev/null
+++ b/test/unit/tile.js
@@ -0,0 +1,204 @@
+'use strict';
+
+var fs = require('fs');
+var path = require('path');
+var assert = require('assert');
+
+var async = require('async');
+var rimraf = require('rimraf');
+
+var sharp = require('../../index');
+var fixtures = require('../fixtures');
+
+sharp.cache(0);
+
+// Verifies all tiles in a given dz output directory are <= size
+var assertDeepZoomTiles = function(directory, expectedSize, expectedLevels, done) {
+  // Get levels
+  var levels = fs.readdirSync(directory);
+  assert.strictEqual(expectedLevels, levels.length);
+  // Get tiles
+  var tiles = [];
+  levels.forEach(function(level) {
+    // Verify level directory name
+    assert.strictEqual(true, /^[0-9]+$/.test(level));
+    fs.readdirSync(path.join(directory, level)).forEach(function(tile) {
+      // Verify tile file name
+      assert.strictEqual(true, /^[0-9]+_[0-9]+\.jpeg$/.test(tile));
+      tiles.push(path.join(directory, level, tile));
+    });
+  });
+  // Verify each tile is <= expectedSize
+  async.eachSeries(tiles, function(tile, done) {
+    sharp(tile).metadata(function(err, metadata) {
+      if (err) {
+        done(err);
+      } else {
+        assert.strictEqual('jpeg', metadata.format);
+        assert.strictEqual('srgb', metadata.space);
+        assert.strictEqual(3, metadata.channels);
+        assert.strictEqual(false, metadata.hasProfile);
+        assert.strictEqual(false, metadata.hasAlpha);
+        assert.strictEqual(true, metadata.width <= expectedSize);
+        assert.strictEqual(true, metadata.height <= expectedSize);
+        done();
+      }
+    });
+  }, done);
+};
+
+describe('Tile', function() {
+
+  describe('Invalid tile values', function() {
+    it('size - NaN', function(done) {
+      var isValid = true;
+      try {
+        sharp().tile('zoinks');
+      } catch (err) {
+        isValid = false;
+      }
+      assert.strictEqual(false, isValid);
+      done();
+    });
+
+    it('size - float', function(done) {
+      var isValid = true;
+      try {
+        sharp().tile(1.1);
+      } catch (err) {
+        isValid = false;
+      }
+      assert.strictEqual(false, isValid);
+      done();
+    });
+
+    it('size - negative', function(done) {
+      var isValid = true;
+      try {
+        sharp().tile(-1);
+      } catch (err) {
+        isValid = false;
+      }
+      assert.strictEqual(false, isValid);
+      done();
+    });
+
+    it('size - zero', function(done) {
+      var isValid = true;
+      try {
+        sharp().tile(0);
+      } catch (err) {
+        isValid = false;
+      }
+      assert.strictEqual(false, isValid);
+      done();
+    });
+
+    it('size - too large', function(done) {
+      var isValid = true;
+      try {
+        sharp().tile(8193);
+      } catch (err) {
+        isValid = false;
+      }
+      assert.strictEqual(false, isValid);
+      done();
+    });
+
+    it('overlap - NaN', function(done) {
+      var isValid = true;
+      try {
+        sharp().tile(null, 'zoinks');
+      } catch (err) {
+        isValid = false;
+      }
+      assert.strictEqual(false, isValid);
+      done();
+    });
+
+    it('overlap - float', function(done) {
+      var isValid = true;
+      try {
+        sharp().tile(null, 1.1);
+      } catch (err) {
+        isValid = false;
+      }
+      assert.strictEqual(false, isValid);
+      done();
+    });
+
+    it('overlap - negative', function(done) {
+      var isValid = true;
+      try {
+        sharp().tile(null, -1);
+      } catch (err) {
+        isValid = false;
+      }
+      assert.strictEqual(false, isValid);
+      done();
+    });
+
+    it('overlap - too large', function(done) {
+      var isValid = true;
+      try {
+        sharp().tile(null, 8193);
+      } catch (err) {
+        isValid = false;
+      }
+      assert.strictEqual(false, isValid);
+      done();
+    });
+
+    it('overlap - larger than default size', function(done) {
+      var isValid = true;
+      try {
+        sharp().tile(null, 257);
+      } catch (err) {
+        isValid = false;
+      }
+      assert.strictEqual(false, isValid);
+      done();
+    });
+
+    it('overlap - larger than provided size', function(done) {
+      var isValid = true;
+      try {
+        sharp().tile(512, 513);
+      } catch (err) {
+        isValid = false;
+      }
+      assert.strictEqual(false, isValid);
+      done();
+    });
+
+  });
+
+  if (sharp.format.dz.output.file) {
+    describe('Deep Zoom output', function() {
+
+      it('Tile size - 256px default', function(done) {
+        var directory = fixtures.path('output256_files');
+        rimraf(directory, function() {
+          sharp(fixtures.inputJpg).toFile(fixtures.path('output256.dzi'), function(err, info) {
+            if (err) throw err;
+            assert.strictEqual('dz', info.format);
+            assertDeepZoomTiles(directory, 256, 13, done);
+          });
+        });
+      });
+
+      it('Tile size/overlap - 512/16px', function(done) {
+        var directory = fixtures.path('output512_files');
+        rimraf(directory, function() {
+          sharp(fixtures.inputJpg).tile(512, 16).toFile(fixtures.path('output512.dzi'), function(err, info) {
+            if (err) throw err;
+            assert.strictEqual('dz', info.format);
+            assertDeepZoomTiles(directory, 512 + 2 * 16, 13, done);
+          });
+        });
+      });
+
+    });
+  }
+
+});