Add support for mirroring #62

README.md

@@ -321,7 +321,15 @@ Rotate the output image by either an explicit angle or auto-orient based on the
 
 `angle`, if present, is a Number with a value of `0`, `90`, `180` or `270`.
 
-Use this method without `angle` to determine the angle from EXIF data. Mirroring is currently unsupported.
+Use this method without `angle` to determine the angle from EXIF data. Mirroring is supported and may infer the use of a `flip` operation.
+
+#### flip()
+
+Flip the image about the vertical Y axis. This always occurs after rotation, if any.
+
+#### flop()
+
+Flop the image about the horizontal X axis. This always occurs after rotation, if any.
 
 #### withoutEnlargement()
 

index.js

@@ -31,6 +31,8 @@ var Sharp = function(input) {
     canvas: 'c',
     gravity: 0,
     angle: 0,
+    flip: false,
+    flop: false,
     withoutEnlargement: false,
     interpolator: 'bilinear',
     // operations
@@ -168,6 +170,22 @@ Sharp.prototype.rotate = function(angle) {
   return this;
 };
 
+/*
+  Flip the image vertically, about the Y axis
+*/
+Sharp.prototype.flip = function(flip) {
+  this.options.flip = (typeof flip === 'boolean') ? flip : true;
+  return this;
+};
+
+/*
+  Flop the image horizontally, about the X axis
+*/
+Sharp.prototype.flop = function(flop) {
+  this.options.flop = (typeof flop === 'boolean') ? flop : true;
+  return this;
+};
+
 /*
   Do not enlarge the output if the input width *or* height are already less than the required dimensions
   This is equivalent to GraphicsMagick's ">" geometry option:

src/sharp.cc

@@ -43,12 +43,14 @@ struct resize_baton {
   bool sharpen;
   double gamma;
   bool greyscale;
+  int angle;
+  bool flip;
+  bool flop;
   bool progressive;
   bool without_enlargement;
   VipsAccess access_method;
   int quality;
   int compression_level;
-  int angle;
   std::string err;
   bool with_metadata;
 
@@ -65,6 +67,8 @@ struct resize_baton {
     sharpen(false),
     gamma(0.0),
     greyscale(false),
+    flip(false),
+    flop(false),
     progressive(false),
     without_enlargement(false),
     with_metadata(false) {}
@@ -125,15 +129,16 @@ typedef enum {
 } Angle;
 
 /*
-  Calculate the angle of rotation for the output image.
+  Calculate the angle of rotation and need-to-flip for the output image.
   In order of priority:
    1. Use explicitly requested angle (supports 90, 180, 270)
-   2. Use input image EXIF Orientation header (does not support mirroring)
+   2. Use input image EXIF Orientation header - supports mirroring
    3. Otherwise default to zero, i.e. no rotation
 */
-static Angle
-sharp_calc_rotation(int const angle, VipsImage const *input) {
+static std::tuple<Angle, bool>
+sharp_calc_rotation_and_flip(int const angle, VipsImage const *input) {
   Angle rotate = ANGLE_0;
+  bool flip = FALSE;
   if (angle == -1) {
     const char *exif;
     if (!vips_image_get_string(input, "exif-ifd0-Orientation", &exif)) {
@@ -143,6 +148,17 @@ sharp_calc_rotation(int const angle, VipsImage const *input) {
         rotate = ANGLE_180;
       } else if (exif[0] == 0x38) { // "8"
         rotate = ANGLE_270;
+      } else if (exif[0] == 0x32) { // "2" (flip 1)
+        flip = TRUE;
+      } else if (exif[0] == 0x37) { // "7" (flip 6)
+        rotate = ANGLE_90;
+        flip = TRUE;
+      } else if (exif[0] == 0x34) { // "4" (flip 3)
+        rotate = ANGLE_180;
+        flip = TRUE;
+      } else if (exif[0] == 0x35) { // "5" (flip 8)
+        rotate = ANGLE_270;
+        flip = TRUE;
       }
     }
   } else {
@@ -154,7 +170,7 @@ sharp_calc_rotation(int const angle, VipsImage const *input) {
       rotate = ANGLE_270;
     }
   }
-  return rotate;
+  return std::make_tuple(rotate, flip);
 }
 
 /*
@@ -443,13 +459,19 @@ class ResizeWorker : public NanAsyncWorker {
     int inputHeight = image->Ysize;
 
     // Calculate angle of rotation, to be carried out later
-    Angle rotation = sharp_calc_rotation(baton->angle, image);
+    Angle rotation;
+    bool flip;
+    std::tie(rotation, flip) = sharp_calc_rotation_and_flip(baton->angle, image);
     if (rotation == ANGLE_90 || rotation == ANGLE_270) {
       // Swap input output width and height when rotating by 90 or 270 degrees
       int swap = inputWidth;
       inputWidth = inputHeight;
       inputHeight = swap;
     }
+    if (flip && !baton->flip) {
+      // Add flip operation due to EXIF mirroring
+      baton->flip = TRUE;
+    }
 
     // Scaling calculations
     double factor;
@@ -645,6 +667,28 @@ class ResizeWorker : public NanAsyncWorker {
       image = rotated;
     }
 
+    // Flip (mirror about Y axis)
+    if (baton->flip) {
+      VipsImage *flipped = vips_image_new();
+      vips_object_local(hook, flipped);
+      if (vips_flip(image, &flipped, VIPS_DIRECTION_VERTICAL, NULL)) {
+        return resize_error(baton, hook);
+      }
+      g_object_unref(image);
+      image = flipped;
+    }
+
+    // Flop (mirror about X axis)
+    if (baton->flop) {
+      VipsImage *flopped = vips_image_new();
+      vips_object_local(hook, flopped);
+      if (vips_flip(image, &flopped, VIPS_DIRECTION_HORIZONTAL, NULL)) {
+        return resize_error(baton, hook);
+      }
+      g_object_unref(image);
+      image = flopped;
+    }
+
     // Crop/embed
     if (image->Xsize != baton->width || image->Ysize != baton->height) {
       if (baton->canvas == EMBED) {
@@ -960,6 +1004,8 @@ NAN_METHOD(resize) {
   baton->gamma = options->Get(NanNew<String>("gamma"))->NumberValue();
   baton->greyscale = options->Get(NanNew<String>("greyscale"))->BooleanValue();
   baton->angle = options->Get(NanNew<String>("angle"))->Int32Value();
+  baton->flip = options->Get(NanNew<String>("flip"))->BooleanValue();
+  baton->flop = options->Get(NanNew<String>("flop"))->BooleanValue();
   // Output options
   baton->progressive = options->Get(NanNew<String>("progressive"))->BooleanValue();
   baton->quality = options->Get(NanNew<String>("quality"))->Int32Value();

test/fixtures/index.js

@@ -10,6 +10,7 @@ module.exports = {
 
   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
   inputJpgWithGammaHoliness: getPath('gamma_dalai_lama_gray.jpg'), // http://www.4p8.com/eric.brasseur/gamma.html
   inputJpgWithCmykProfile: getPath('Channel_digital_image_CMYK_color.jpg'), // http://en.wikipedia.org/wiki/File:Channel_digital_image_CMYK_color.jpg
 

test/unit/rotate.js

@@ -19,7 +19,9 @@ describe('Rotation', function() {
   });
 
   it('Input image has Orientation EXIF tag but do not rotate output', function(done) {
-    sharp(fixtures.inputJpgWithExif).resize(320).toBuffer(function(err, data, info) {
+    sharp(fixtures.inputJpgWithExif)
+      .resize(320)
+      .toBuffer(function(err, data, info) {
         if (err) throw err;
         assert.strictEqual(true, data.length > 0);
         assert.strictEqual('jpeg', info.format);
@@ -30,9 +32,24 @@ describe('Rotation', function() {
   });
 
   it('Input image has Orientation EXIF tag value of 8 (270 degrees), auto-rotate', function(done) {
-    sharp(fixtures.inputJpgWithExif).rotate().resize(320).toBuffer(function(err, data, info) {
+    sharp(fixtures.inputJpgWithExif)
+      .rotate()
+      .resize(320)
+      .toFile(fixtures.path('output.exif.8.jpg'), function(err, info) {
+        if (err) throw err;
+        assert.strictEqual('jpeg', info.format);
+        assert.strictEqual(320, info.width);
+        assert.strictEqual(240, info.height);
+        done();
+      });
+  });
+
+  it('Input image has Orientation EXIF tag value of 5 (270 degrees + flip), auto-rotate', function(done) {
+    sharp(fixtures.inputJpgWithExifMirroring)
+      .rotate()
+      .resize(320)
+      .toFile(fixtures.path('output.exif.5.jpg'), function(err, 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);
@@ -61,4 +78,57 @@ describe('Rotation', function() {
     done();
   });
 
+  it('Flip - vertical', function(done) {
+    sharp(fixtures.inputJpg)
+      .resize(320)
+      .flip()
+      .toFile(fixtures.path('output.flip.jpg'), function(err, info) {
+        if (err) throw err;
+        assert.strictEqual('jpeg', info.format);
+        assert.strictEqual(320, info.width);
+        assert.strictEqual(261, info.height);
+        done();
+      });
+  });
+
+  it('Flop - horizontal', function(done) {
+    sharp(fixtures.inputJpg)
+      .resize(320)
+      .flop()
+      .toFile(fixtures.path('output.flop.jpg'), function(err, info) {
+        if (err) throw err;
+        assert.strictEqual('jpeg', info.format);
+        assert.strictEqual(320, info.width);
+        assert.strictEqual(261, info.height);
+        done();
+      });
+  });
+
+  it('Flip and flop', function(done) {
+    sharp(fixtures.inputJpg)
+      .resize(320)
+      .flop()
+      .toFile(fixtures.path('output.flip.flop.jpg'), function(err, info) {
+        if (err) throw err;
+        assert.strictEqual('jpeg', info.format);
+        assert.strictEqual(320, info.width);
+        assert.strictEqual(261, info.height);
+        done();
+      });
+  });
+
+  it('Neither flip nor flop', function(done) {
+    sharp(fixtures.inputJpg)
+      .resize(320)
+      .flip(false)
+      .flop(false)
+      .toFile(fixtures.path('output.flip.flop.nope.jpg'), function(err, info) {
+        if (err) throw err;
+        assert.strictEqual('jpeg', info.format);
+        assert.strictEqual(320, info.width);
+        assert.strictEqual(261, info.height);
+        done();
+      });
+  });
+
 });