EXIF Orientation tags 2 and 4 were flipping instead of flopping

src/pipeline.cc

@@ -250,11 +250,16 @@ class PipelineWorker : public AsyncWorker {
     // Calculate angle of rotation
     Angle rotation;
     bool flip;
-    std::tie(rotation, flip) = CalculateRotationAndFlip(baton->angle, image);
+    bool flop;
+    std::tie(rotation, flip, flop) = CalculateRotationAndFlip(baton->angle, image);
     if (flip && !baton->flip) {
       // Add flip operation due to EXIF mirroring
       baton->flip = TRUE;
     }
+    if (flop && !baton->flop) {
+      // Add flip operation due to EXIF mirroring
+      baton->flop = TRUE;
+    }
 
     // Rotate pre-extract
     if (baton->rotateBeforePreExtract && rotation != Angle::D0) {
@@ -1041,18 +1046,19 @@ class PipelineWorker : public AsyncWorker {
      2. Use input image EXIF Orientation header - supports mirroring
      3. Otherwise default to zero, i.e. no rotation
   */
-  std::tuple<Angle, bool>
+  std::tuple<Angle, bool, bool>
   CalculateRotationAndFlip(int const angle, VipsImage const *input) {
     Angle rotate = Angle::D0;
     bool flip = FALSE;
+    bool flop = FALSE;
     if (angle == -1) {
       switch(ExifOrientation(input)) {
         case 6: rotate = Angle::D90; break;
         case 3: rotate = Angle::D180; break;
         case 8: rotate = Angle::D270; break;
-        case 2: flip = TRUE; break; // flip 1
+        case 2: flop = TRUE; break; // flop 1
         case 7: flip = TRUE; rotate = Angle::D90; break; // flip 6
-        case 4: flip = TRUE; rotate = Angle::D180; break; // flip 3
+        case 4: flop = TRUE; rotate = Angle::D180; break; // flop 3
         case 5: flip = TRUE; rotate = Angle::D270; break; // flip 8
       }
     } else {
@@ -1064,7 +1070,7 @@ class PipelineWorker : public AsyncWorker {
         rotate = Angle::D270;
       }
     }
-    return std::make_tuple(rotate, flip);
+    return std::make_tuple(rotate, flip, flop);
   }
 
   /*
@@ -1240,3 +1246,4 @@ NAN_METHOD(pipeline) {
   Local<Value> queueLength[1] = { New<Uint32>(counterQueue) };
   queueListener->Call(1, queueLength);
 }
+

test/fixtures/index.js

@@ -40,6 +40,24 @@ var fingerprint = function(image, callback) {
 
 module.exports = {
 
+  inputJpgWithLandscapeExif1: getPath('Landscape_1.jpg'), // https://github.com/recurser/exif-orientation-examples
+  inputJpgWithLandscapeExif2: getPath('Landscape_2.jpg'), // https://github.com/recurser/exif-orientation-examples
+  inputJpgWithLandscapeExif3: getPath('Landscape_3.jpg'), // https://github.com/recurser/exif-orientation-examples
+  inputJpgWithLandscapeExif4: getPath('Landscape_4.jpg'), // https://github.com/recurser/exif-orientation-examples
+  inputJpgWithLandscapeExif5: getPath('Landscape_5.jpg'), // https://github.com/recurser/exif-orientation-examples
+  inputJpgWithLandscapeExif6: getPath('Landscape_6.jpg'), // https://github.com/recurser/exif-orientation-examples
+  inputJpgWithLandscapeExif7: getPath('Landscape_7.jpg'), // https://github.com/recurser/exif-orientation-examples
+  inputJpgWithLandscapeExif8: getPath('Landscape_8.jpg'), // https://github.com/recurser/exif-orientation-examples
+
+  inputJpgWithPortraitExif1: getPath('Portrait_1.jpg'), // https://github.com/recurser/exif-orientation-examples
+  inputJpgWithPortraitExif2: getPath('Portrait_2.jpg'), // https://github.com/recurser/exif-orientation-examples
+  inputJpgWithPortraitExif3: getPath('Portrait_3.jpg'), // https://github.com/recurser/exif-orientation-examples
+  inputJpgWithPortraitExif4: getPath('Portrait_4.jpg'), // https://github.com/recurser/exif-orientation-examples
+  inputJpgWithPortraitExif5: getPath('Portrait_5.jpg'), // https://github.com/recurser/exif-orientation-examples
+  inputJpgWithPortraitExif6: getPath('Portrait_6.jpg'), // https://github.com/recurser/exif-orientation-examples
+  inputJpgWithPortraitExif7: getPath('Portrait_7.jpg'), // https://github.com/recurser/exif-orientation-examples
+  inputJpgWithPortraitExif8: getPath('Portrait_8.jpg'), // https://github.com/recurser/exif-orientation-examples
+
   inputJpg: getPath('2569067123_aca715a2ee_o.jpg'), // http://www.flickr.com/photos/grizdave/2569067123/
   inputJpgWithExif: getPath('Landscape_8.jpg'), // https://github.com/recurser/exif-orientation-examples/blob/master/Landscape_8.jpg
   inputJpgWithExifMirroring: getPath('Landscape_5.jpg'), // https://github.com/recurser/exif-orientation-examples/blob/master/Landscape_5.jpg

test/unit/rotate.js

@@ -9,6 +9,23 @@ sharp.cache(0);
 
 describe('Rotation', function() {
 
+  ['Landscape', 'Portrait'].forEach(function(orientation) {
+    [1,2,3,4,5,6,7,8].forEach(function(exifTag) {
+      it('Input image has Orientation EXIF tag value of (' + exifTag + '), auto-rotate', function(done) {
+        sharp(fixtures['inputJpgWith'+orientation+'Exif'+exifTag])
+          .rotate()
+          .resize(320)
+          .toBuffer(function(err, data, info) {
+            if (err) throw err;
+            assert.strictEqual('jpeg', info.format);
+            assert.strictEqual(320, info.width);
+            assert.strictEqual(orientation === 'Landscape' ? 240 : 427, info.height);
+            fixtures.assertSimilar(fixtures.expected(orientation + '_' + exifTag + '-out.jpg'), data, done);
+          });
+      });
+    });
+  });
+
   it('Rotate by 90 degrees, respecting output input size', function(done) {
     sharp(fixtures.inputJpg).rotate(90).resize(320, 240).toBuffer(function(err, data, info) {
       if (err) throw err;