Expose density metadata; set density of images from vector input

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),