Fix embedding onto transparent backgrounds #366

Fully automate embed tests to prevent regression

docs/changelog.md

@@ -2,6 +2,12 @@
 
 ### v0.13 - "*mind*"
 
+#### v0.13.1 - TBD
+
+* Fix embedding onto transparent backgrounds; regression introduced in v0.13.0.
+  [#366](https://github.com/lovell/sharp/issues/366)
+  [@diegocsandrim](https://github.com/diegocsandrim)
+
 #### v0.13.0 - 15<sup>th</sup> February 2016
 
 * Improve vector image support by allowing control of density/DPI.

src/pipeline.cc

@@ -585,9 +585,9 @@ class PipelineWorker : public AsyncWorker {
           }
           // Add non-transparent alpha channel, if required
           if (baton->background[3] < 255.0 && !HasAlpha(image)) {
-            VImage alpha = VImage::new_matrix(image.width(), image.height())
-              .new_from_image(baton->background[3] * multiplier);
-            image = image.bandjoin(alpha);
+            image = image.bandjoin(
+              VImage::new_matrix(image.width(), image.height()).new_from_image(255 * multiplier)
+            );
           }
           // Embed
           int left = static_cast<int>(round((baton->width - image.width()) / 2));

test/unit/alpha.js

@@ -60,31 +60,25 @@ describe('Alpha transparency', function() {
   it('Do not flatten', function(done) {
     sharp(fixtures.inputPngWithTransparency)
       .flatten(false)
-      .toBuffer(function(err, data) {
+      .toBuffer(function(err, data, info) {
         if (err) throw err;
-        sharp(data).metadata(function(err, metadata) {
-          if (err) throw err;
-          assert.strictEqual('png', metadata.format);
-          assert.strictEqual(4, metadata.channels);
+        assert.strictEqual('png', info.format);
+        assert.strictEqual(4, info.channels);
         done();
       });
   });
-  });
 
   it('Ignored for JPEG', function(done) {
     sharp(fixtures.inputJpg)
       .background('#ff0000')
       .flatten()
-      .toBuffer(function(err, data) {
+      .toBuffer(function(err, data, info) {
         if (err) throw err;
-        sharp(data).metadata(function(err, metadata) {
-          if (err) throw err;
-          assert.strictEqual('jpeg', metadata.format);
-          assert.strictEqual(3, metadata.channels);
+        assert.strictEqual('jpeg', info.format);
+        assert.strictEqual(3, info.channels);
         done();
       });
   });
-  });
 
   it('Enlargement with non-nearest neighbor interpolation shouldn’t cause dark edges', function(done) {
     var BASE_NAME = 'alpha-premultiply-enlargement-2048x1536-paper.png';

test/unit/embed.js

@@ -18,11 +18,8 @@ describe('Embed', function() {
         assert.strictEqual('png', info.format);
         assert.strictEqual(320, info.width);
         assert.strictEqual(240, info.height);
-        sharp(data).metadata(function(err, metadata) {
-          if (err) throw err;
-          assert.strictEqual(3, metadata.channels);
-          done();
-        });
+        assert.strictEqual(3, info.channels);
+        fixtures.assertSimilar(fixtures.expected('embed-3-into-3.png'), data, done);
       });
   });
 
@@ -39,11 +36,8 @@ describe('Embed', function() {
           assert.strictEqual('webp', info.format);
           assert.strictEqual(320, info.width);
           assert.strictEqual(240, info.height);
-          sharp(data).metadata(function(err, metadata) {
-            if (err) throw err;
-            assert.strictEqual(4, metadata.channels);
-            done();
-          });
+          assert.strictEqual(4, info.channels);
+          fixtures.assertSimilar(fixtures.expected('embed-3-into-4.webp'), data, done);
         });
     });
   }
@@ -58,11 +52,8 @@ describe('Embed', function() {
         assert.strictEqual('png', info.format);
         assert.strictEqual(50, info.width);
         assert.strictEqual(50, info.height);
-        sharp(data).metadata(function(err, metadata) {
-          if (err) throw err;
-          assert.strictEqual(4, metadata.channels);
-          done();
-        });
+        assert.strictEqual(4, info.channels);
+        fixtures.assertSimilar(fixtures.expected('embed-4-into-4.png'), data, done);
       });
   });
 
@@ -76,6 +67,7 @@ describe('Embed', function() {
         assert.strictEqual('png', info.format);
         assert.strictEqual(32, info.width);
         assert.strictEqual(16, info.height);
+        assert.strictEqual(4, info.channels);
         fixtures.assertSimilar(fixtures.expected('embed-16bit.png'), data, done);
       });
   });
@@ -91,6 +83,7 @@ describe('Embed', function() {
         assert.strictEqual('png', info.format);
         assert.strictEqual(32, info.width);
         assert.strictEqual(16, info.height);
+        assert.strictEqual(4, info.channels);
         fixtures.assertSimilar(fixtures.expected('embed-16bit-rgba.png'), data, done);
       });
   });
@@ -105,6 +98,7 @@ describe('Embed', function() {
         assert.strictEqual('png', info.format);
         assert.strictEqual(320, info.width);
         assert.strictEqual(240, info.height);
+        assert.strictEqual(3, info.channels);
         fixtures.assertSimilar(fixtures.expected('embed-enlarge.png'), data, done);
       });
   });