Prevent crop when at or below target dimensions lovell#1134

Author: lovell

docs/changelog.md

@@ -14,6 +14,10 @@ Requires libvips v8.6.1.
   [#1121](https://github.com/lovell/sharp/pull/1121)
   [@BiancoA](https://github.com/BiancoA)
 
+* Prevent crop operation when image already at or below target dimensions.
+  [#1134](https://github.com/lovell/sharp/issues/1134)
+  [@pieh](https://github.com/pieh)
+
 #### v0.19.0 - 11<sup>th</sup> January 2018
 
 * Expose offset coordinates of strategy-based crop.

src/pipeline.cc

@@ -465,7 +465,10 @@ class PipelineWorker : public Nan::AsyncWorker {
             ->set("extend", VIPS_EXTEND_BACKGROUND)
             ->set("background", background));
 
-        } else if (baton->canvas != Canvas::IGNORE_ASPECT) {
+        } else if (
+          baton->canvas != Canvas::IGNORE_ASPECT &&
+          (image.width() > baton->width || image.height() > baton->height)
+        ) {
           // Crop/max/min
           if (baton->crop < 9) {
             // Gravity-based crop

test/unit/crop.js

@@ -159,6 +159,24 @@ describe('Crop', function () {
     });
   });
 
+  it('Skip crop when post-resize dimensions are at or below target dimensions', function () {
+    return sharp(fixtures.inputJpg)
+      .resize(1600, 1200)
+      .toBuffer()
+      .then(function (input) {
+        return sharp(input)
+          .resize(1110)
+          .crop(sharp.strategy.attention)
+          .toBuffer({ resolveWithObject: true })
+          .then(function (result) {
+            assert.strictEqual(1110, result.info.width);
+            assert.strictEqual(832, result.info.height);
+            assert.strictEqual(undefined, result.info.cropOffsetLeft);
+            assert.strictEqual(undefined, result.info.cropOffsetTop);
+          });
+      });
+  });
+
   describe('Entropy-based strategy', function () {
     it('JPEG', function (done) {
       sharp(fixtures.inputJpg)