From 969e882bea99f1d9754b2419482de7a6fe665653 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Marcin=20Sk=C3=B3rzewski?= <marcin.skorzewski@gmail.com>
Date: Wed, 29 Apr 2015 17:41:10 +0200
Subject: [PATCH] Allow arbitrary gravity shifts when cropping

---
 index.js      | 15 ++++++++++++---
 src/resize.cc | 38 ++++++++++++--------------------------
 2 files changed, 24 insertions(+), 29 deletions(-)

diff --git a/index.js b/index.js
index a10833347..cba585550 100755
--- a/index.js
+++ b/index.js
@@ -43,7 +43,7 @@ var Sharp = function(input) {
     width: -1,
     height: -1,
     canvas: 'crop',
-    gravity: 0,
+    gravity: { left: 0.5, top: 0.5 },
     angle: 0,
     rotateBeforePreExtract: false,
     flip: false,
@@ -132,11 +132,20 @@ Sharp.prototype._write = function(chunk, encoding, callback) {
 };
 
 // Crop this part of the resized image (Center/Centre, North, East, South, West)
-module.exports.gravity = {'center': 0, 'centre': 0, 'north': 1, 'east': 2, 'south': 3, 'west': 4};
+module.exports.gravity = {
+  'center': { left: 0.5, top: 0.5 },
+  'centre': { left: 0.5, top: 0.5 },
+  'north':  { left: 0.5, top: 0.0 },
+  'east':   { left: 1.0, top: 0.5 },
+  'south':  { left: 0.5, top: 1.0 },
+  'west':   { left: 0.0, top: 0.5 }
+};
 
 Sharp.prototype.crop = function(gravity) {
   this.options.canvas = 'crop';
-  if (typeof gravity === 'number' && !Number.isNaN(gravity) && gravity >= 0 && gravity <= 4) {
+  if (typeof gravity === 'object' &&
+      typeof gravity.left === 'number' && !Number.isNaN(gravity.left) && gravity.left >= 0 && gravity.left <= 1 &&
+      typeof gravity.top === 'number' && !Number.isNaN(gravity.top) && gravity.top >= 0 && gravity.top <= 1) {
     this.options.gravity = gravity;
   } else {
     throw new Error('Unsupported crop gravity ' + gravity);
diff --git a/src/resize.cc b/src/resize.cc
index 93ade321c..063deb059 100755
--- a/src/resize.cc
+++ b/src/resize.cc
@@ -73,7 +73,8 @@ struct ResizeBaton {
   int width;
   int height;
   Canvas canvas;
-  int gravity;
+  double gravityLeft;
+  double gravityTop;
   std::string interpolator;
   double background[4];
   bool flatten;
@@ -111,7 +112,8 @@ struct ResizeBaton {
     topOffsetPre(-1),
     topOffsetPost(-1),
     canvas(Canvas::CROP),
-    gravity(0),
+    gravityLeft(0.5),
+    gravityTop(0.5),
     flatten(false),
     blurSigma(0.0),
     sharpenRadius(0),
@@ -619,7 +621,7 @@ class ResizeWorker : public NanAsyncWorker {
         // Crop/max/min
         int left;
         int top;
-        std::tie(left, top) = CalculateCrop(image->Xsize, image->Ysize, baton->width, baton->height, baton->gravity);
+        std::tie(left, top) = CalculateCrop(image->Xsize, image->Ysize, baton->width, baton->height, baton->gravityLeft, baton->gravityTop);
         int width = std::min(image->Xsize, baton->width);
         int height = std::min(image->Ysize, baton->height);
         VipsImage *extracted;
@@ -1054,28 +1056,10 @@ class ResizeWorker : public NanAsyncWorker {
     within the input image, applying the given gravity.
   */
   std::tuple<int, int>
-  CalculateCrop(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 = (inWidth - outWidth + 1) / 2;
-        break;
-      case 2: // East
-        left = inWidth - outWidth;
-        top = (inHeight - outHeight + 1) / 2;
-        break;
-      case 3: // South
-        left = (inWidth - outWidth + 1) / 2;
-        top = inHeight - outHeight;
-        break;
-      case 4: // West
-        top = (inHeight - outHeight + 1) / 2;
-        break;
-      default: // Centre
-        left = (inWidth - outWidth + 1) / 2;
-        top = (inHeight - outHeight + 1) / 2;
-    }
+  CalculateCrop(int const inWidth, int const inHeight, int const outWidth, int const outHeight,
+      double const gravityLeft, double const gravityTop) {
+    int left = (inWidth - outWidth) * gravityLeft;
+    int top = (inHeight - outHeight) * gravityTop;
     return std::make_tuple(left, top);
   }
 
@@ -1177,7 +1161,9 @@ NAN_METHOD(resize) {
   }
   // Resize options
   baton->withoutEnlargement = options->Get(NanNew<String>("withoutEnlargement"))->BooleanValue();
-  baton->gravity = options->Get(NanNew<String>("gravity"))->Int32Value();
+  Local<Object> gravity = options->Get(NanNew<String>("gravity"))->ToObject();
+  baton->gravityLeft = gravity->Get(NanNew<String>("left"))->NumberValue();
+  baton->gravityTop = gravity->Get(NanNew<String>("top"))->NumberValue();
   baton->interpolator = *String::Utf8Value(options->Get(NanNew<String>("interpolator"))->ToString());
   // Operators
   baton->flatten = options->Get(NanNew<String>("flatten"))->BooleanValue();