Merge 6f2715b into acc6059

lovell · May 6, 2015 · be5f437 · be5f437
2 parents acc6059 + 6f2715b
commit be5f437
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Showing 8 changed files with 48 additions and 10 deletions.
diff --git a/README.md b/README.md
@@ -440,6 +440,10 @@ Do not enlarge the output image if the input image width *or* height are already
 
 This is equivalent to GraphicsMagick's `>` geometry option: "change the dimensions of the image only if its width or height exceeds the geometry specification".
 
+#### withoutGaussianBlur()
+
+Do not apply a Gaussian blur for large image reductions. Applying a Gaussian blur on images with alpha channel can introduce dark fringing around bright parts.
+
 #### blur([sigma])
 
 When used without parameters, performs a fast, mild blur of the output image. This typically reduces performance by 10%.

diff --git a/index.js b/index.js
@@ -42,6 +42,7 @@ var Sharp = function(input) {
     heightPost: -1,
     width: -1,
     height: -1,
+    withoutGaussianBlur: false,
     canvas: 'crop',
     gravity: 0,
     angle: 0,
@@ -257,6 +258,15 @@ Sharp.prototype.withoutEnlargement = function(withoutEnlargement) {
   return this;
 };
 
+/*
+  Do not apply a Gaussian blur. This is useful to avoid dark ‘fringing’ around bright pixels when doing
+  large reductions on images with transparency.
+*/
+Sharp.prototype.withoutGaussianBlur = function(withoutGaussianBlur) {
+  this.options.withoutGaussianBlur = (typeof withoutGaussianBlur === 'boolean') ? withoutGaussianBlur : true;
+  return this;
+};
+
 /*
   Blur the output image.
   Call without a sigma to use a fast, mild blur.

diff --git a/src/resize.cc b/src/resize.cc
@@ -92,6 +92,7 @@ struct ResizeBaton {
   bool flop;
   bool progressive;
   bool withoutEnlargement;
+  bool withoutGaussianBlur;
   VipsAccess accessMethod;
   int quality;
   int compressionLevel;
@@ -127,6 +128,7 @@ struct ResizeBaton {
     flop(false),
     progressive(false),
     withoutEnlargement(false),
+    withoutGaussianBlur(false),
     quality(80),
     compressionLevel(6),
     withoutAdaptiveFiltering(false),
@@ -485,7 +487,7 @@ class ResizeWorker : public NanAsyncWorker {
       // Use average of x and y residuals to compute sigma for Gaussian blur
       double residual = (xresidual + yresidual) / 2.0;
       // Apply Gaussian blur before large affine reductions
-      if (residual < 1.0) {
+      if (residual < 1.0 && !baton->withoutGaussianBlur) {
         // Calculate standard deviation
         double sigma = ((1.0 / residual) - 0.4) / 3.0;
         if (sigma >= 0.3) {
@@ -1229,6 +1231,7 @@ NAN_METHOD(resize) {
   baton->overlayPath = *String::Utf8Value(options->Get(NanNew<String>("overlayPath"))->ToString());
   // Resize options
   baton->withoutEnlargement = options->Get(NanNew<String>("withoutEnlargement"))->BooleanValue();
+  baton->withoutGaussianBlur = options->Get(NanNew<String>("withoutGaussianBlur"))->BooleanValue();
   baton->gravity = options->Get(NanNew<String>("gravity"))->Int32Value();
   baton->interpolator = *String::Utf8Value(options->Get(NanNew<String>("interpolator"))->ToString());
   // Operators

diff --git a/test/fixtures/alpha-resizing-2048x1536-paper.png b/test/fixtures/alpha-resizing-2048x1536-paper.png
diff --git a/test/fixtures/expected/alpha-resizing-bicubic-gaussian-blur-1024x768.png b/test/fixtures/expected/alpha-resizing-bicubic-gaussian-blur-1024x768.png
diff --git a/test/fixtures/expected/alpha-resizing-bicubic-no-gaussian-blur-1024x768.png b/test/fixtures/expected/alpha-resizing-bicubic-no-gaussian-blur-1024x768.png
diff --git a/test/fixtures/index.js b/test/fixtures/index.js
@@ -52,6 +52,7 @@ module.exports = {
   inputPngWithTransparency: getPath('blackbug.png'), // public domain
   inputPngWithGreyAlpha: getPath('grey-8bit-alpha.png'),
   inputPngWithOneColor: getPath('2x2_fdcce6.png'),
+  inputPngWithFineBrightDetails: getPath('alpha-resizing-2048x1536-paper.png'),
   inputPngOverlayLayer0: getPath('alpha-layer-0-background.png'),
   inputPngOverlayLayer1: getPath('alpha-layer-1-fill.png'),
   inputPngOverlayLayer2: getPath('alpha-layer-2-ink.png'),

diff --git a/test/unit/resize.js b/test/unit/resize.js
@@ -259,7 +259,7 @@ describe('Resize dimensions', function() {
         done();
       });
   });
-  
+
   it('Downscale width and height, ignoring aspect ratio', function(done) {
     sharp(fixtures.inputJpg).resize(320, 320).ignoreAspectRatio().toBuffer(function(err, data, info) {
       if (err) throw err;
@@ -270,7 +270,27 @@ describe('Resize dimensions', function() {
       done();
     });
   });
-
+
+  it('Large reduction of transparent image with Gaussian blur', function(done) {
+    sharp(fixtures.inputPngWithFineBrightDetails).resize(1024, 768).interpolateWith('bicubic').toBuffer(function(err, data, info) {
+      if (err) throw err;
+      assert.strictEqual('png', info.format);
+      assert.strictEqual(1024, info.width);
+      assert.strictEqual(768, info.height);
+      fixtures.assertSimilar(fixtures.expected('alpha-resizing-bicubic-gaussian-blur-1024x768.png'), data, {threshold: 0}, done);
+    });
+  });
+
+  it('Large reduction of transparent image without Gaussian blur', function(done) {
+    sharp(fixtures.inputPngWithFineBrightDetails).resize(1024, 768).interpolateWith('bicubic').withoutGaussianBlur().toBuffer(function(err, data, info) {
+      if (err) throw err;
+      assert.strictEqual('png', info.format);
+      assert.strictEqual(1024, info.width);
+      assert.strictEqual(768, info.height);
+      fixtures.assertSimilar(fixtures.expected('alpha-resizing-bicubic-no-gaussian-blur-1024x768.png'), data, {threshold: 0}, done);
+    });
+  });
+
   it('Downscale width, ignoring aspect ratio', function(done) {
     sharp(fixtures.inputJpg).resize(320).ignoreAspectRatio().toBuffer(function(err, data, info) {
       if (err) throw err;
@@ -281,7 +301,7 @@ describe('Resize dimensions', function() {
       done();
     });
   });
-  
+
   it('Downscale height, ignoring aspect ratio', function(done) {
     sharp(fixtures.inputJpg).resize(null, 320).ignoreAspectRatio().toBuffer(function(err, data, info) {
       if (err) throw err;
@@ -292,7 +312,7 @@ describe('Resize dimensions', function() {
       done();
     });
   });
-  
+
   it('Upscale width and height, ignoring aspect ratio', function(done) {
     sharp(fixtures.inputJpg).resize(3000, 3000).ignoreAspectRatio().toBuffer(function(err, data, info) {
       if (err) throw err;
@@ -303,7 +323,7 @@ describe('Resize dimensions', function() {
       done();
     });
   });
-  
+
   it('Upscale width, ignoring aspect ratio', function(done) {
     sharp(fixtures.inputJpg).resize(3000).ignoreAspectRatio().toBuffer(function(err, data, info) {
       if (err) throw err;
@@ -314,7 +334,7 @@ describe('Resize dimensions', function() {
       done();
     });
   });
-  
+
   it('Upscale height, ignoring aspect ratio', function(done) {
     sharp(fixtures.inputJpg).resize(null, 3000).ignoreAspectRatio().toBuffer(function(err, data, info) {
       if (err) throw err;
@@ -325,7 +345,7 @@ describe('Resize dimensions', function() {
       done();
     });
   });
-  
+
   it('Downscale width, upscale height, ignoring aspect ratio', function(done) {
     sharp(fixtures.inputJpg).resize(320, 3000).ignoreAspectRatio().toBuffer(function(err, data, info) {
       if (err) throw err;
@@ -336,7 +356,7 @@ describe('Resize dimensions', function() {
       done();
     });
   });
-  
+
   it('Upscale width, downscale height, ignoring aspect ratio', function(done) {
     sharp(fixtures.inputJpg).resize(3000, 320).ignoreAspectRatio().toBuffer(function(err, data, info) {
       if (err) throw err;
@@ -347,7 +367,7 @@ describe('Resize dimensions', function() {
       done();
     });
   });
-  
+
   it('Identity transform, ignoring aspect ratio', function(done) {
     sharp(fixtures.inputJpg).ignoreAspectRatio().toBuffer(function(err, data, info) {
       if (err) throw err;