Add support for bicubic and Nohalo interpolation #41

README.md

@@ -53,7 +53,7 @@ Compiling from source is recommended:
 	cd libvips
 	git checkout 7.38
 	./bootstrap.sh
-	./configure --enable-debug=no --enable-cxx=no --without-python --without-orc
+	./configure --enable-debug=no --enable-cxx=yes --without-python --without-orc
 	make
 	sudo make install
 	sudo ldconfig
@@ -100,8 +100,8 @@ sharp('input.png').rotate(180).resize(300).sharpen().quality(90).webp().then(fun
 ```
 
 ```javascript
-sharp(inputBuffer).resize(200, 300).embedWhite().toFile('output.tiff').then(function() {
-  // output.tiff is a 200 pixels wide and 300 pixels high image containing a scaled
+sharp(inputBuffer).resize(200, 300).bicubicInterpolation().embedWhite().toFile('output.tiff').then(function() {
+  // output.tiff is a 200 pixels wide and 300 pixels high image containing a bicubic scaled
   // version, embedded on a white canvas, of the image data in buffer
 });
 ```
@@ -176,6 +176,18 @@ This is equivalent to GraphicsMagick's `>` geometry option: "change the dimensio
 
 Perform a mild sharpen of the resultant image. This typically reduces performance by 30%.
 
+### bilinearInterpolation()
+
+Use [bilinear interpolation](http://en.wikipedia.org/wiki/Bilinear_interpolation) for image resizing, the default (and fastest) interpolation if none is specified.
+
+### bicubicInterpolation()
+
+Use [bicubic interpolation](http://en.wikipedia.org/wiki/Bicubic_interpolation) for image resizing. This typically reduces performance by 5%.
+
+### nohaloInterpolation()
+
+Use [Nohalo interpolation](http://eprints.soton.ac.uk/268086/) for image resizing. This typically reduces performance by a factor of 2.
+
 ### progressive()
 
 Use progressive (interlace) scan for JPEG and PNG output. This typically reduces compression performance by 30% but results in an image that can be rendered sooner when decompressed.

index.js

@@ -16,6 +16,7 @@ var Sharp = function(input) {
     angle: 0,
     withoutEnlargement: false,
     sharpen: false,
+    interpolator: 'bilinear',
     progressive: false,
     sequentialRead: false,
 		quality: 80,
@@ -87,6 +88,30 @@ Sharp.prototype.sharpen = function(sharpen) {
   return this;
 };
 
+/*
+  Use bilinear interpolation for the affine transformation (fastest, default)
+*/
+Sharp.prototype.bilinearInterpolation = function() {
+  this.options.interpolator = 'bilinear';
+  return this;
+};
+
+/*
+  Use bicubic interpolation for the affine transformation
+*/
+Sharp.prototype.bicubicInterpolation = function() {
+  this.options.interpolator = 'bicubic';
+  return this;
+};
+
+/*
+  Use Nohalo interpolation for the affine transformation
+*/
+Sharp.prototype.nohaloInterpolation = function() {
+  this.options.interpolator = 'nohalo';
+  return this;
+};
+
 Sharp.prototype.progressive = function(progressive) {
   this.options.progressive = (typeof progressive === 'boolean') ? progressive : true;
   return this;

src/sharp.cc

@@ -23,6 +23,7 @@ struct resize_baton {
   bool max;
   VipsExtend extend;
   bool sharpen;
+  std::string interpolator;
   bool progressive;
   bool without_enlargement;
   VipsAccess access_method;
@@ -294,12 +295,17 @@ class ResizeWorker : public NanAsyncWorker {
     }
     g_object_unref(shrunk_on_load);
 
-    // Use vips_affine with the remaining float part using bilinear interpolation
+    // Use vips_affine with the remaining float part
     VipsImage *affined = vips_image_new();
     if (residual != 0) {
-      if (vips_affine(shrunk, &affined, residual, 0, 0, residual, "interpolate", vips_interpolate_bilinear_static(), NULL)) {
+      // Create interpolator - "bilinear" (default), "bicubic" or "nohalo"
+      VipsInterpolate *interpolator = vips_interpolate_new(baton->interpolator.c_str());
+      // Perform affine transformation
+      if (vips_affine(shrunk, &affined, residual, 0, 0, residual, "interpolate", interpolator, NULL)) {
+        g_object_unref(interpolator);
         return resize_error(baton, shrunk);
       }
+      g_object_unref(interpolator);
     } else {
       vips_copy(shrunk, &affined, NULL);
     }
@@ -461,6 +467,7 @@ NAN_METHOD(resize) {
   }
   // Other options
   baton->sharpen = options->Get(NanNew<String>("sharpen"))->BooleanValue();
+  baton->interpolator = *String::Utf8Value(options->Get(NanNew<String>("interpolator"))->ToString());
   baton->progressive = options->Get(NanNew<String>("progressive"))->BooleanValue();
   baton->without_enlargement = options->Get(NanNew<String>("withoutEnlargement"))->BooleanValue();
   baton->access_method = options->Get(NanNew<String>("sequentialRead"))->BooleanValue() ? VIPS_ACCESS_SEQUENTIAL : VIPS_ACCESS_RANDOM;

tests/perf.js

@@ -166,6 +166,30 @@ async.series({
           }
         });
       }
+    }).add("sharp-file-buffer-bicubic", {
+      defer: true,
+      fn: function(deferred) {
+        sharp(inputJpg).resize(width, height).bicubicInterpolation().toBuffer(function(err, buffer) {
+          if (err) {
+            throw err;
+          } else {
+            assert.notStrictEqual(null, buffer);
+            deferred.resolve();
+          }
+        });
+      }
+    }).add("sharp-file-buffer-nohalo", {
+      defer: true,
+      fn: function(deferred) {
+        sharp(inputJpg).resize(width, height).nohaloInterpolation().toBuffer(function(err, buffer) {
+          if (err) {
+            throw err;
+          } else {
+            assert.notStrictEqual(null, buffer);
+            deferred.resolve();
+          }
+        });
+      }
     }).add("sharp-file-buffer-progressive", {
       defer: true,
       fn: function(deferred) {

tests/unit.js

@@ -268,5 +268,41 @@ async.series([
     sharp(inputTiff).webp().then(function() {
       done();
     });
-  }
+  },
+  // Interpolation: bilinear
+  function(done) {
+    sharp(inputJpg).resize(320, 240).bilinearInterpolation().toFile(outputJpg, function(err) {
+      if (err) throw err;
+      imagemagick.identify(outputJpg, function(err, features) {
+        if (err) throw err;
+        assert.strictEqual(320, features.width);
+        assert.strictEqual(240, features.height);
+        done();
+      });
+    });
+  },
+  // Interpolation: bicubic
+  function(done) {
+    sharp(inputJpg).resize(320, 240).bicubicInterpolation().toFile(outputJpg, function(err) {
+      if (err) throw err;
+      imagemagick.identify(outputJpg, function(err, features) {
+        if (err) throw err;
+        assert.strictEqual(320, features.width);
+        assert.strictEqual(240, features.height);
+        done();
+      });
+    });
+  },
+  // Interpolation: nohalo
+  function(done) {
+    sharp(inputJpg).resize(320, 240).nohaloInterpolation().toFile(outputJpg, function(err) {
+      if (err) throw err;
+      imagemagick.identify(outputJpg, function(err, features) {
+        if (err) throw err;
+        assert.strictEqual(320, features.width);
+        assert.strictEqual(240, features.height);
+        done();
+      });
+    });
+  },
 ]);