Ensure correct ordering of rotate-then-trim ops #2087

docs/changelog.md

@@ -14,6 +14,9 @@ Requires libvips v8.9.1
 * Add support for 32-bit Windows.
   [#2088](https://github.com/lovell/sharp/issues/2088)
 
+* Ensure correct ordering of rotate-then-trim operations.
+  [#2087](https://github.com/lovell/sharp/issues/2087)
+
 ## v0.24 - "*wit*"
 
 Requires libvips v8.9.0.

lib/resize.js

@@ -85,6 +85,13 @@ const mapFitToCanvas = {
   outside: 'min'
 };
 
+/**
+ * @private
+ */
+function isRotationExpected (options) {
+  return (options.angle % 360) !== 0 || options.useExifOrientation === true || options.rotationAngle !== 0;
+}
+
 /**
  * Resize image to `width`, `height` or `width x height`.
  *
@@ -367,7 +374,7 @@ function extract (options) {
     }
   }, this);
   // Ensure existing rotation occurs before pre-resize extraction
-  if (suffix === 'Pre' && ((this.options.angle % 360) !== 0 || this.options.useExifOrientation === true || this.options.rotationAngle !== 0)) {
+  if (suffix === 'Pre' && isRotationExpected(this.options)) {
     this.options.rotateBeforePreExtract = true;
   }
   return this;
@@ -391,6 +398,9 @@ function trim (threshold) {
   } else {
     throw is.invalidParameterError('threshold', 'number greater than zero', threshold);
   }
+  if (this.options.trimThreshold && isRotationExpected(this.options)) {
+    this.options.rotateBeforePreExtract = true;
+  }
   return this;
 }
 

test/unit/trim.js

@@ -94,6 +94,32 @@ describe('Trim borders', function () {
       .catch(done);
   });
 
+  it('should rotate before trim', () =>
+    sharp({
+      create: {
+        width: 20,
+        height: 30,
+        channels: 3,
+        background: 'white'
+      }
+    })
+      .rotate(30)
+      .png()
+      .toBuffer()
+      .then(rotated30 =>
+        sharp(rotated30)
+          .rotate(-30)
+          .trim(128)
+          .toBuffer({ resolveWithObject: true })
+          .then(({ info }) => {
+            assert.strictEqual(20, info.width);
+            assert.strictEqual(31, info.height);
+            assert.strictEqual(-8, info.trimOffsetTop);
+            assert.strictEqual(-13, info.trimOffsetLeft);
+          })
+      )
+  );
+
   describe('Invalid thresholds', function () {
     [-1, 'fail', {}].forEach(function (threshold) {
       it(JSON.stringify(threshold), function () {