Add margin option to trim operation #4480

test/fixtures/index.js

@@ -74,6 +74,7 @@ module.exports = {
 
   inputPng: getPath('50020484-00001.png'), // http://c.searspartsdirect.com/lis_png/PLDM/50020484-00001.png
   inputPngGradients: getPath('gradients-rgb8.png'),
+  inputPngWithSlightGradientBorder: getPath('slight-gradient-border.png'),
   inputPngWithTransparency: getPath('blackbug.png'), // public domain
   inputPngCompleteTransparency: getPath('full-transparent.png'),
   inputPngWithGreyAlpha: getPath('grey-8bit-alpha.png'),

test/types/sharp.test-d.ts

@@ -599,7 +599,7 @@ const vertexSplitQuadraticBasisSpline: string = sharp.interpolators.vertexSplitQ
 // Triming
 sharp(input).trim({ background: '#000' }).toBuffer();
 sharp(input).trim({ threshold: 10, lineArt: true }).toBuffer();
-sharp(input).trim({ background: '#bf1942', threshold: 30 }).toBuffer();
+sharp(input).trim({ background: '#bf1942', threshold: 30, margin: 20 }).toBuffer();
 
 // Text input
 sharp({

test/unit/trim.js

@@ -222,6 +222,9 @@ describe('Trim borders', () => {
       },
       'Invalid lineArt': {
         lineArt: 'fail'
+      },
+      'Invalid margin': {
+        margin: -1
       }
     }).forEach(([description, parameter]) => {
       it(description, () => {
@@ -289,4 +292,42 @@ describe('Trim borders', () => {
       assert.strictEqual(trimOffsetLeft, 0);
     });
   });
+
+  describe('Adds margin around content', () => {
+    it('Should trim complex gradients', async () => {
+      const { info } = await sharp(fixtures.inputPngGradients)
+        .trim({ threshold: 50, margin: 100 })
+        .toBuffer({ resolveWithObject: true });
+
+      const { width, height, trimOffsetTop, trimOffsetLeft } = info;
+      assert.strictEqual(width, 1000);
+      assert.strictEqual(height, 443);
+      assert.strictEqual(trimOffsetTop, -557);
+      assert.strictEqual(trimOffsetLeft, 0);
+    });
+
+    it('Should trim simple gradients', async () => {
+      const { info } = await sharp(fixtures.inputPngWithSlightGradientBorder)
+        .trim({ threshold: 70, margin: 50 })
+        .toBuffer({ resolveWithObject: true });
+
+      const { width, height, trimOffsetTop, trimOffsetLeft } = info;
+      assert.strictEqual(width, 900);
+      assert.strictEqual(height, 900);
+      assert.strictEqual(trimOffsetTop, -50);
+      assert.strictEqual(trimOffsetLeft, -50);
+    });
+
+    it('Should not overflow image bounding box', async () => {
+      const { info } = await sharp(fixtures.inputPngWithSlightGradientBorder)
+        .trim({ threshold: 70, margin: 9999999 })
+        .toBuffer({ resolveWithObject: true });
+
+      const { width, height, trimOffsetTop, trimOffsetLeft } = info;
+      assert.strictEqual(width, 1000);
+      assert.strictEqual(height, 1000);
+      assert.strictEqual(trimOffsetTop, 0);
+      assert.strictEqual(trimOffsetLeft, 0);
+    });
+  });
 });