Add gravity support to embed feature (lovell#1038)

Author: AzureByte

lib/constructor.js

@@ -136,6 +136,7 @@ const Sharp = function (input, options) {
     height: -1,
     canvas: 'crop',
     crop: 0,
+    embed: 0,
     useExifOrientation: false,
     angle: 0,
     rotateBeforePreExtract: false,

lib/resize.js

@@ -179,11 +179,26 @@ function crop (crop) {
  *     // outputBuffer contains WebP image data of a 200 pixels wide and 300 pixels high
  *     // containing a scaled version, embedded on a transparent canvas, of input.gif
  *   });
- *
+ * @param {String} [embed='centre'] - A member of `sharp.gravity` to embed to an edge/corner.
  * @returns {Sharp}
+ * @throws {Error} Invalid parameters
  */
-function embed () {
+function embed (embed) {
   this.options.canvas = 'embed';
+
+  if (!is.defined(embed)) {
+    // Default
+    this.options.embed = gravity.center;
+  } else if (is.integer(embed) && is.inRange(embed, 0, 8)) {
+    // Gravity (numeric)
+    this.options.embed = embed;
+  } else if (is.string(embed) && is.integer(gravity[embed])) {
+    // Gravity (string)
+    this.options.embed = gravity[embed];
+  } else {
+    throw is.invalidParameterError('embed', 'valid embed id/name', embed);
+  }
+
   return this;
 }
 

package.json

@@ -40,7 +40,8 @@
     "Nicolas Coden <nicolas@ncoden.fr>",
     "Matt Parrish <matt.r.parrish@gmail.com>",
     "Matthew McEachen <matthew+github@mceachen.org>",
-    "Jarda Kotěšovec <jarda.kotesovec@gmail.com>"
+    "Jarda Kotěšovec <jarda.kotesovec@gmail.com>",
+    "Kenric D'Souza <kenric.dsouza@gmail.com>"
   ],
   "scripts": {
     "clean": "rm -rf node_modules/ build/ vendor/ coverage/ test/fixtures/output.*",
@@ -66,6 +67,7 @@
     "resize",
     "thumbnail",
     "crop",
+    "embed",
     "libvips",
     "vips"
   ],

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),