Add gravity support to embed feature (#1038)

src/common.cc

@@ -409,7 +409,62 @@ namespace sharp {
 
   /*
     Calculate the (left, top) coordinates of the output image
-    within the input image, applying the given gravity.
+    within the input image, applying the given gravity during an embed.
+
+    @Azurebyte: We are basically swapping the inWidth and outWidth, inHeight and outHeight from the CalculateCrop function.
+  */
+  std::tuple<int, int> CalculateEmbedPosition(int const inWidth, int const inHeight,
+    int const outWidth, int const outHeight, int const gravity) {
+
+    int left = 0;
+    int top = 0;
+    switch (gravity) {
+      case 1:
+        // North
+        left = (outWidth - inWidth) / 2;
+        break;
+      case 2:
+        // East
+        left = outWidth - inWidth;
+        top = (outHeight - inHeight) / 2;
+        break;
+      case 3:
+        // South
+        left = (outWidth - inWidth) / 2;
+        top = outHeight - inHeight;
+        break;
+      case 4:
+        // West
+        top = (outHeight - inHeight) / 2;
+        break;
+      case 5:
+        // Northeast
+        left = outWidth - inWidth;
+        break;
+      case 6:
+        // Southeast
+        left = outWidth - inWidth;
+        top = outHeight - inHeight;
+        break;
+      case 7:
+        // Southwest
+        top = outHeight - inHeight;
+        break;
+      case 8:
+        // Northwest
+        // Which is the default is 0,0 so we do not assign anything here.
+        break;
+      default:
+        // Centre
+        left = (outWidth - inWidth) / 2;
+        top = (outHeight - inHeight) / 2;
+    }
+    return std::make_tuple(left, top);
+  }
+
+  /*
+    Calculate the (left, top) coordinates of the output image
+    within the input image, applying the given gravity during a crop.
   */
   std::tuple<int, int> CalculateCrop(int const inWidth, int const inHeight,
     int const outWidth, int const outHeight, int const gravity) {

src/common.h

@@ -206,6 +206,13 @@ namespace sharp {
   */
   std::string VipsWarningPop();
 
+  /*
+    Calculate the (left, top) coordinates of the output image
+    within the input image, applying the given gravity during an embed.
+  */
+  std::tuple<int, int> CalculateEmbedPosition(int const inWidth, int const inHeight,
+    int const outWidth, int const outHeight, int const gravity);
+
   /*
     Calculate the (left, top) coordinates of the output image
     within the input image, applying the given gravity.

src/pipeline.cc

@@ -446,12 +446,25 @@ class PipelineWorker : public Nan::AsyncWorker {
             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));
-          int top = static_cast<int>(round((baton->height - image.height()) / 2));
-          image = image.embed(left, top, baton->width, baton->height, VImage::option()
+
+          // Calculate where to position the embeded image if gravity specified, else center.
+          int left;
+          int top;
+
+          left = static_cast<int>(round((baton->width - image.width()) / 2));
+          top = static_cast<int>(round((baton->height - image.height()) / 2));
+
+          int width = std::max(image.width(), baton->width);
+          int height = std::max(image.height(), baton->height);
+          std::tie(left, top) = sharp::CalculateEmbedPosition(
+            image.width(), image.height(), baton->width, baton->height, baton->embed);
+
+          image = image.embed(left, top, width, height, VImage::option()
             ->set("extend", VIPS_EXTEND_BACKGROUND)
             ->set("background", background));
+
         } else if (baton->canvas != Canvas::IGNORE_ASPECT) {
           // Crop/max/min
           if (baton->crop < 9) {
@@ -1141,6 +1154,7 @@ NAN_METHOD(pipeline) {
   // Resize options
   baton->withoutEnlargement = AttrTo<bool>(options, "withoutEnlargement");
   baton->crop = AttrTo<int32_t>(options, "crop");
+  baton->embed = AttrTo<int32_t>(options, "embed");
   baton->kernel = AttrAsStr(options, "kernel");
   baton->fastShrinkOnLoad = AttrTo<bool>(options, "fastShrinkOnLoad");
   // Join Channel Options

src/pipeline.h

@@ -62,6 +62,7 @@ struct PipelineBaton {
   int channels;
   Canvas canvas;
   int crop;
+  int embed;
   bool hasCropOffset;
   int cropOffsetLeft;
   int cropOffsetTop;
@@ -145,6 +146,7 @@ struct PipelineBaton {
     channels(0),
     canvas(Canvas::CROP),
     crop(0),
+    embed(0),
     hasCropOffset(false),
     cropOffsetLeft(0),
     cropOffsetTop(0),