From 0725378257e6752e0cfb0521a72f77dfb4b3f658 Mon Sep 17 00:00:00 2001
From: Lovell Fuller <github@lovell.info>
Date: Tue, 2 Oct 2018 20:16:00 +0100
Subject: [PATCH] Add trimOffsetLeft, trimOffsetTop to trim response #914

---
 docs/api-resize.md | 1 +
 lib/resize.js      | 1 +
 src/pipeline.cc    | 8 ++++++++
 src/pipeline.h     | 4 ++++
 test/unit/trim.js  | 6 ++++++
 5 files changed, 20 insertions(+)

diff --git a/docs/api-resize.md b/docs/api-resize.md
index a33c93aeb..e6e60e39c 100644
--- a/docs/api-resize.md
+++ b/docs/api-resize.md
@@ -196,6 +196,7 @@ Returns **Sharp**
 ## trim
 
 Trim "boring" pixels from all edges that contain values similar to the top-left pixel.
+The `info` response Object will contain `trimOffsetLeft` and `trimOffsetTop` properties.
 
 ### Parameters
 
diff --git a/lib/resize.js b/lib/resize.js
index 06f190fb5..72e409bda 100644
--- a/lib/resize.js
+++ b/lib/resize.js
@@ -361,6 +361,7 @@ function extract (options) {
 
 /**
  * Trim "boring" pixels from all edges that contain values similar to the top-left pixel.
+ * The `info` response Object will contain `trimOffsetLeft` and `trimOffsetTop` properties.
  * @param {Number} [threshold=10] the allowed difference from the top-left pixel, a number greater than zero.
  * @returns {Sharp}
  * @throws {Error} Invalid parameters
diff --git a/src/pipeline.cc b/src/pipeline.cc
index 6193c9cee..61bc79661 100644
--- a/src/pipeline.cc
+++ b/src/pipeline.cc
@@ -102,6 +102,8 @@ class PipelineWorker : public Nan::AsyncWorker {
       // Trim
       if (baton->trimThreshold > 0.0) {
         image = sharp::Trim(image, baton->trimThreshold);
+        baton->trimOffsetLeft = image.xoffset();
+        baton->trimOffsetTop = image.yoffset();
       }
 
       // Pre extraction
@@ -966,6 +968,12 @@ class PipelineWorker : public Nan::AsyncWorker {
         Set(info, New("cropOffsetTop").ToLocalChecked(),
           New<v8::Int32>(static_cast<int32_t>(baton->cropOffsetTop)));
       }
+      if (baton->trimThreshold > 0.0) {
+        Set(info, New("trimOffsetLeft").ToLocalChecked(),
+          New<v8::Int32>(static_cast<int32_t>(baton->trimOffsetLeft)));
+        Set(info, New("trimOffsetTop").ToLocalChecked(),
+          New<v8::Int32>(static_cast<int32_t>(baton->trimOffsetTop)));
+      }
 
       if (baton->bufferOutLength > 0) {
         // Pass ownership of output data to Buffer instance
diff --git a/src/pipeline.h b/src/pipeline.h
index 8d1fa80ae..cd763a869 100644
--- a/src/pipeline.h
+++ b/src/pipeline.h
@@ -82,6 +82,8 @@ struct PipelineBaton {
   int threshold;
   bool thresholdGrayscale;
   double trimThreshold;
+  int trimOffsetLeft;
+  int trimOffsetTop;
   double linearA;
   double linearB;
   double gamma;
@@ -177,6 +179,8 @@ struct PipelineBaton {
     threshold(0),
     thresholdGrayscale(true),
     trimThreshold(0.0),
+    trimOffsetLeft(0),
+    trimOffsetTop(0),
     linearA(1.0),
     linearB(0.0),
     gamma(0.0),
diff --git a/test/unit/trim.js b/test/unit/trim.js
index 39ba632bb..709b5f0a3 100644
--- a/test/unit/trim.js
+++ b/test/unit/trim.js
@@ -16,6 +16,8 @@ describe('Trim borders', function () {
         assert.strictEqual('png', info.format);
         assert.strictEqual(450, info.width);
         assert.strictEqual(322, info.height);
+        assert.strictEqual(-204, info.trimOffsetLeft);
+        assert.strictEqual(0, info.trimOffsetTop);
         fixtures.assertSimilar(expected, data, done);
       });
   });
@@ -29,6 +31,8 @@ describe('Trim borders', function () {
         if (err) throw err;
         assert.strictEqual('jpeg', info.format);
         assert.strictEqual(300, info.width);
+        assert.strictEqual(-873, info.trimOffsetLeft);
+        assert.strictEqual(-554, info.trimOffsetTop);
         fixtures.assertSimilar(expected, data, done);
       });
   });
@@ -44,6 +48,8 @@ describe('Trim borders', function () {
         assert.strictEqual(32, info.width);
         assert.strictEqual(32, info.height);
         assert.strictEqual(4, info.channels);
+        assert.strictEqual(-2, info.trimOffsetLeft);
+        assert.strictEqual(-2, info.trimOffsetTop);
         fixtures.assertSimilar(fixtures.expected('trim-16bit-rgba.png'), data, done);
       });
   });