Expose density metadata; set density of images from vector input

docs/api.md

@@ -48,6 +48,7 @@ Fast access to image metadata without decoding any compressed image data.
 * `height`: Number of pixels high
 * `space`: Name of colour space interpretation e.g. `srgb`, `rgb`, `scrgb`, `cmyk`, `lab`, `xyz`, `b-w` [...](https://github.com/jcupitt/libvips/blob/master/libvips/iofuncs/enumtypes.c#L522)
 * `channels`: Number of bands e.g. `3` for sRGB, `4` for CMYK
+* `density`: Number of pixels per inch (DPI), if present
 * `hasProfile`: Boolean indicating the presence of an embedded ICC profile
 * `hasAlpha`: Boolean indicating the presence of an alpha transparency channel
 * `orientation`: Number value of the EXIF Orientation header, if present

docs/changelog.md

@@ -6,6 +6,10 @@
   [#239](https://github.com/lovell/sharp/issues/239)
   [@chrisriley](https://github.com/chrisriley)
 
+* Expose density metadata; set density of images from vector input.
+  [#338](https://github.com/lovell/sharp/issues/338)
+  [@lookfirst](https://github.com/lookfirst)
+
 ### v0.13 - "*mind*"
 
 #### v0.13.1 - 27<sup>th</sup> February 2016

index.js

@@ -46,7 +46,7 @@ var Sharp = function(input, options) {
     streamIn: false,
     sequentialRead: false,
     limitInputPixels: maximum.pixels,
-    density: '72',
+    density: 72,
     rawWidth: 0,
     rawHeight: 0,
     rawChannels: 0,
@@ -172,7 +172,7 @@ Sharp.prototype._inputOptions = function(options) {
     // Density
     if (isDefined(options.density)) {
       if (isInteger(options.density) && inRange(options.density, 1, 2400)) {
-        this.options.density = options.density.toString();
+        this.options.density = options.density;
       } else {
         throw new Error('Invalid density (1 to 2400) ' + options.density);
       }

src/common.cc

@@ -176,6 +176,30 @@ namespace sharp {
     SetExifOrientation(image, 0);
   }
 
+  /*
+    Does this image have a non-default density?
+  */
+  bool HasDensity(VImage image) {
+    return image.xres() > 1.0;
+  }
+
+  /*
+    Get pixels/mm resolution as pixels/inch density.
+  */
+  int GetDensity(VImage image) {
+    return static_cast<int>(round(image.xres() * 25.4));
+  }
+
+  /*
+    Set pixels/mm resolution based on a pixels/inch density.
+  */
+  void SetDensity(VImage image, const int density) {
+    const double pixelsPerMm = static_cast<double>(density) / 25.4;
+    image.set("Xres", pixelsPerMm);
+    image.set("Yres", pixelsPerMm);
+    image.set(VIPS_META_RESOLUTION_UNIT, "in");
+  }
+
   /*
     Called when a Buffer undergoes GC, required to support mixed runtime libraries in Windows
   */

src/common.h

@@ -77,6 +77,21 @@ namespace sharp {
   */
   void RemoveExifOrientation(VImage image);
 
+  /*
+    Does this image have a non-default density?
+  */
+  bool HasDensity(VImage image);
+
+  /*
+    Get pixels/mm resolution as pixels/inch density.
+  */
+  int GetDensity(VImage image);
+
+  /*
+    Set pixels/mm resolution based on a pixels/inch density.
+  */
+  void SetDensity(VImage image, const int density);
+
   /*
     Called when a Buffer undergoes GC, required to support mixed runtime libraries in Windows
   */

src/metadata.cc

@@ -38,6 +38,8 @@ using sharp::DetermineImageType;
 using sharp::HasProfile;
 using sharp::HasAlpha;
 using sharp::ExifOrientation;
+using sharp::HasDensity;
+using sharp::GetDensity;
 using sharp::FreeCallback;
 using sharp::counterQueue;
 
@@ -52,6 +54,7 @@ struct MetadataBaton {
   int height;
   std::string space;
   int channels;
+  int density;
   bool hasProfile;
   bool hasAlpha;
   int orientation;
@@ -63,6 +66,7 @@ struct MetadataBaton {
 
   MetadataBaton():
     bufferInLength(0),
+    density(0),
     orientation(0),
     exifLength(0),
     iccLength(0) {}
@@ -120,6 +124,9 @@ class MetadataWorker : public AsyncWorker {
       baton->height = image.height();
       baton->space = vips_enum_nick(VIPS_TYPE_INTERPRETATION, image.interpretation());
       baton->channels = image.bands();
+      if (HasDensity(image)) {
+        baton->density = GetDensity(image);
+      }
       baton->hasProfile = HasProfile(image);
       // Derived attributes
       baton->hasAlpha = HasAlpha(image);
@@ -161,6 +168,9 @@ class MetadataWorker : public AsyncWorker {
       Set(info, New("height").ToLocalChecked(), New<Number>(baton->height));
       Set(info, New("space").ToLocalChecked(), New<String>(baton->space).ToLocalChecked());
       Set(info, New("channels").ToLocalChecked(), New<Number>(baton->channels));
+      if (baton->density > 0) {
+        Set(info, New("density").ToLocalChecked(), New<Number>(baton->density));
+      }
       Set(info, New("hasProfile").ToLocalChecked(), New<Boolean>(baton->hasProfile));
       Set(info, New("hasAlpha").ToLocalChecked(), New<Boolean>(baton->hasAlpha));
       if (baton->orientation > 0) {

src/operations.cc

@@ -169,4 +169,5 @@ namespace sharp {
       );
     }
   }
+
 }  // namespace sharp

src/operations.h

@@ -32,6 +32,7 @@ namespace sharp {
    * Sharpen flat and jagged areas. Use radius of -1 for fast sharpen.
    */
   VImage Sharpen(VImage image, int const radius, double const flat, double const jagged);
+
 }  // namespace sharp
 
 #endif  // SRC_OPERATIONS_H_

src/pipeline.cc

@@ -58,6 +58,7 @@ using sharp::HasAlpha;
 using sharp::ExifOrientation;
 using sharp::SetExifOrientation;
 using sharp::RemoveExifOrientation;
+using sharp::SetDensity;
 using sharp::IsJpeg;
 using sharp::IsPng;
 using sharp::IsWebp;
@@ -118,9 +119,12 @@ class PipelineWorker : public AsyncWorker {
           try {
             VOption *option = VImage::option()->set("access", baton->accessMethod);
             if (inputImageType == ImageType::MAGICK) {
-              option->set("density", baton->density.data());
+              option->set("density", std::to_string(baton->density).data());
             }
             image = VImage::new_from_buffer(baton->bufferIn, baton->bufferInLength, nullptr, option);
+            if (inputImageType == ImageType::MAGICK) {
+              SetDensity(image, baton->density);
+            }
           } catch (...) {
             (baton->err).append("Input buffer has corrupt header");
             inputImageType = ImageType::UNKNOWN;
@@ -136,9 +140,12 @@ class PipelineWorker : public AsyncWorker {
         try {
           VOption *option = VImage::option()->set("access", baton->accessMethod);
           if (inputImageType == ImageType::MAGICK) {
-            option->set("density", baton->density.data());
+            option->set("density", std::to_string(baton->density).data());
           }
           image = VImage::new_from_file(baton->fileIn.data(), option);
+          if (inputImageType == ImageType::MAGICK) {
+            SetDensity(image, baton->density);
+          }
         } catch (...) {
           (baton->err).append("Input file has corrupt header");
           inputImageType = ImageType::UNKNOWN;
@@ -921,7 +928,7 @@ NAN_METHOD(pipeline) {
   // Limit input images to a given number of pixels, where pixels = width * height
   baton->limitInputPixels = attrAs<int32_t>(options, "limitInputPixels");
   // Density/DPI at which to load vector images via libmagick
-  baton->density = attrAsStr(options, "density");
+  baton->density = attrAs<int32_t>(options, "density");
   // Raw pixel input
   baton->rawWidth = attrAs<int32_t>(options, "rawWidth");
   baton->rawHeight = attrAs<int32_t>(options, "rawHeight");

src/pipeline.h

@@ -19,7 +19,7 @@ struct PipelineBaton {
   size_t bufferInLength;
   std::string iccProfilePath;
   int limitInputPixels;
-  std::string density;
+  int density;
   int rawWidth;
   int rawHeight;
   int rawChannels;
@@ -79,7 +79,7 @@ struct PipelineBaton {
   PipelineBaton():
     bufferInLength(0),
     limitInputPixels(0),
-    density(""),
+    density(72),
     rawWidth(0),
     rawHeight(0),
     rawChannels(0),

test/unit/io.js

@@ -662,7 +662,14 @@ describe('Input/output', function() {
             assert.strictEqual('png', info.format);
             assert.strictEqual(40, info.width);
             assert.strictEqual(40, info.height);
-            fixtures.assertSimilar(fixtures.expected('svg72.png'), data, done);
+            fixtures.assertSimilar(fixtures.expected('svg72.png'), data, function(err) {
+              if (err) throw err;
+              sharp(data).metadata(function(err, info) {
+                if (err) throw err;
+                assert.strictEqual(72, info.density);
+                done();
+              });
+            });
           }
         });
     });
@@ -679,7 +686,14 @@ describe('Input/output', function() {
             assert.strictEqual('png', info.format);
             assert.strictEqual(40, info.width);
             assert.strictEqual(40, info.height);
-            fixtures.assertSimilar(fixtures.expected('svg1200.png'), data, done);
+            fixtures.assertSimilar(fixtures.expected('svg1200.png'), data, function(err) {
+              if (err) throw err;
+              sharp(data).metadata(function(err, info) {
+                if (err) throw err;
+                assert.strictEqual(1200, info.density);
+                done();
+              });
+            });
           }
         });
     });

test/unit/metadata.js

@@ -18,6 +18,7 @@ describe('Image metadata', function() {
       assert.strictEqual(2225, metadata.height);
       assert.strictEqual('srgb', metadata.space);
       assert.strictEqual(3, metadata.channels);
+      assert.strictEqual('undefined', typeof metadata.density);
       assert.strictEqual(false, metadata.hasProfile);
       assert.strictEqual(false, metadata.hasAlpha);
       assert.strictEqual('undefined', typeof metadata.orientation);
@@ -35,6 +36,7 @@ describe('Image metadata', function() {
       assert.strictEqual(600, metadata.height);
       assert.strictEqual('srgb', metadata.space);
       assert.strictEqual(3, metadata.channels);
+      assert.strictEqual(72, metadata.density);
       assert.strictEqual(true, metadata.hasProfile);
       assert.strictEqual(false, metadata.hasAlpha);
       assert.strictEqual(8, metadata.orientation);
@@ -64,6 +66,7 @@ describe('Image metadata', function() {
         assert.strictEqual(3248, metadata.height);
         assert.strictEqual('b-w', metadata.space);
         assert.strictEqual(1, metadata.channels);
+        assert.strictEqual(300, metadata.density);
         assert.strictEqual(false, metadata.hasProfile);
         assert.strictEqual(false, metadata.hasAlpha);
         assert.strictEqual('undefined', typeof metadata.orientation);
@@ -82,6 +85,7 @@ describe('Image metadata', function() {
       assert.strictEqual(2074, metadata.height);
       assert.strictEqual('b-w', metadata.space);
       assert.strictEqual(1, metadata.channels);
+      assert.strictEqual(300, metadata.density);
       assert.strictEqual(false, metadata.hasProfile);
       assert.strictEqual(false, metadata.hasAlpha);
       assert.strictEqual('undefined', typeof metadata.orientation);
@@ -99,6 +103,7 @@ describe('Image metadata', function() {
       assert.strictEqual(1536, metadata.height);
       assert.strictEqual('srgb', metadata.space);
       assert.strictEqual(4, metadata.channels);
+      assert.strictEqual(72, metadata.density);
       assert.strictEqual(false, metadata.hasProfile);
       assert.strictEqual(true, metadata.hasAlpha);
       assert.strictEqual('undefined', typeof metadata.orientation);
@@ -117,6 +122,7 @@ describe('Image metadata', function() {
         assert.strictEqual(772, metadata.height);
         assert.strictEqual('srgb', metadata.space);
         assert.strictEqual(3, metadata.channels);
+        assert.strictEqual('undefined', typeof metadata.density);
         assert.strictEqual(false, metadata.hasProfile);
         assert.strictEqual(false, metadata.hasAlpha);
         assert.strictEqual('undefined', typeof metadata.orientation);
@@ -135,6 +141,7 @@ describe('Image metadata', function() {
         assert.strictEqual(800, metadata.width);
         assert.strictEqual(533, metadata.height);
         assert.strictEqual(3, metadata.channels);
+        assert.strictEqual('undefined', typeof metadata.density);
         assert.strictEqual(false, metadata.hasProfile);
         assert.strictEqual(false, metadata.hasAlpha);
         assert.strictEqual('undefined', typeof metadata.orientation);
@@ -153,6 +160,7 @@ describe('Image metadata', function() {
         assert.strictEqual(2220, metadata.width);
         assert.strictEqual(2967, metadata.height);
         assert.strictEqual(4, metadata.channels);
+        assert.strictEqual('undefined', typeof metadata.density);
         assert.strictEqual('rgb', metadata.space);
         assert.strictEqual(false, metadata.hasProfile);
         assert.strictEqual(true, metadata.hasAlpha);
@@ -171,6 +179,7 @@ describe('Image metadata', function() {
       assert.strictEqual(2225, metadata.height);
       assert.strictEqual('srgb', metadata.space);
       assert.strictEqual(3, metadata.channels);
+      assert.strictEqual('undefined', typeof metadata.density);
       assert.strictEqual(false, metadata.hasProfile);
       assert.strictEqual(false, metadata.hasAlpha);
       assert.strictEqual('undefined', typeof metadata.orientation);
@@ -198,6 +207,7 @@ describe('Image metadata', function() {
       assert.strictEqual(2225, metadata.height);
       assert.strictEqual('srgb', metadata.space);
       assert.strictEqual(3, metadata.channels);
+      assert.strictEqual('undefined', typeof metadata.density);
       assert.strictEqual(false, metadata.hasProfile);
       assert.strictEqual(false, metadata.hasAlpha);
       assert.strictEqual('undefined', typeof metadata.orientation);
@@ -219,6 +229,7 @@ describe('Image metadata', function() {
       assert.strictEqual(2225, metadata.height);
       assert.strictEqual('srgb', metadata.space);
       assert.strictEqual(3, metadata.channels);
+      assert.strictEqual('undefined', typeof metadata.density);
       assert.strictEqual(false, metadata.hasProfile);
       assert.strictEqual(false, metadata.hasAlpha);
       assert.strictEqual('undefined', typeof metadata.orientation);
@@ -238,6 +249,7 @@ describe('Image metadata', function() {
       assert.strictEqual(2225, metadata.height);
       assert.strictEqual('srgb', metadata.space);
       assert.strictEqual(3, metadata.channels);
+      assert.strictEqual('undefined', typeof metadata.density);
       assert.strictEqual(false, metadata.hasProfile);
       assert.strictEqual(false, metadata.hasAlpha);
       assert.strictEqual('undefined', typeof metadata.orientation);