Add margin option to trim operation #4480

docs/public/humans.txt

@@ -326,3 +326,6 @@ GitHub: https://github.com/tpatel
 
 Name: Maël Nison
 GitHub: https://github.com/arcanis
+
+Name: Dmytro Tiapukhin
+GitHub: https://github.com/eddienubes

docs/src/content/docs/api-resize.md

@@ -284,6 +284,7 @@ The `info` response Object will contain `trimOffsetLeft` and `trimOffsetTop` pro
 | [options.background] | <code>string</code> \| <code>Object</code> | <code>&quot;&#x27;top-left pixel&#x27;&quot;</code> | Background colour, parsed by the [color](https://www.npmjs.org/package/color) module, defaults to that of the top-left pixel. |
 | [options.threshold] | <code>number</code> | <code>10</code> | Allowed difference from the above colour, a positive number. |
 | [options.lineArt] | <code>boolean</code> | <code>false</code> | Does the input more closely resemble line art (e.g. vector) rather than being photographic? |
+| [options.margin] | <code>number</code> | <code>0</code> | Leave a margin around trimmed content, value is in pixels. |
 
 **Example**  
 ```js
@@ -320,4 +321,13 @@ const output = await sharp(input)
     threshold: 42,
   })
   .toBuffer();
+```
+**Example**  
+```js
+// Trim image leaving (up to) a 10 pixel margin around the trimmed content.
+const output = await sharp(input)
+  .trim({
+    margin: 10
+  })
+  .toBuffer();
 ```

docs/src/content/docs/changelog/v0.35.0.md

@@ -34,4 +34,8 @@ slug: changelog/v0.35.0
 * TypeScript: Ensure `FormatEnum` keys match reality.
   [#4475](https://github.com/lovell/sharp/issues/4475)
 
+* Add `margin` option to `trim` operation.
+  [#4480](https://github.com/lovell/sharp/issues/4480)
+  [@eddienubes](https://github.com/eddienubes)
+
 * Add WebP `exact` option for control over transparent pixel colour values.

lib/constructor.js

@@ -278,6 +278,7 @@ const Sharp = function (input, options) {
     trimBackground: [],
     trimThreshold: -1,
     trimLineArt: false,
+    trimMargin: 0,
     dilateWidth: 0,
     erodeWidth: 0,
     gamma: 0,

lib/index.d.ts

@@ -1606,6 +1606,8 @@ declare namespace sharp {
         threshold?: number | undefined;
         /** Does the input more closely resemble line art (e.g. vector) rather than being photographic? (optional, default false) */
         lineArt?: boolean | undefined;
+        /** Leave a margin around trimmed content, value is in pixels. (optional, default 0) */
+        margin?: number | undefined;
     }
 
     interface RawOptions {

lib/resize.js

@@ -540,10 +540,19 @@ function extract (options) {
  *   })
  *   .toBuffer();
  *
+ * @example
+ * // Trim image leaving (up to) a 10 pixel margin around the trimmed content.
+ * const output = await sharp(input)
+ *   .trim({
+ *     margin: 10
+ *   })
+ *   .toBuffer();
+ *
  * @param {Object} [options]
  * @param {string|Object} [options.background='top-left pixel'] - Background colour, parsed by the [color](https://www.npmjs.org/package/color) module, defaults to that of the top-left pixel.
  * @param {number} [options.threshold=10] - Allowed difference from the above colour, a positive number.
  * @param {boolean} [options.lineArt=false] - Does the input more closely resemble line art (e.g. vector) rather than being photographic?
+ * @param {number} [options.margin=0] - Leave a margin around trimmed content, value is in pixels.
  * @returns {Sharp}
  * @throws {Error} Invalid parameters
  */
@@ -564,6 +573,13 @@ function trim (options) {
       if (is.defined(options.lineArt)) {
         this._setBooleanOption('trimLineArt', options.lineArt);
       }
+      if (is.defined(options.margin)) {
+        if (is.integer(options.margin) && options.margin >= 0) {
+          this.options.trimMargin = options.margin;
+        } else {
+          throw is.invalidParameterError('margin', 'positive integer', options.margin);
+        }
+      }
     } else {
       throw is.invalidParameterError('trim', 'object', options);
     }

package.json

@@ -89,7 +89,8 @@
     "Lachlan Newman <lachnewman007@gmail.com>",
     "Dennis Beatty <dennis@dcbeatty.com>",
     "Ingvar Stepanyan <me@rreverser.com>",
-    "Don Denton <don@happycollision.com>"
+    "Don Denton <don@happycollision.com>",
+    "Dmytro Tiapukhin <cool.gegeg@gmail.com>"
   ],
   "scripts": {
     "build": "node install/build.js",

src/operations.cc

@@ -285,7 +285,7 @@ namespace sharp {
   /*
     Trim an image
   */
-  VImage Trim(VImage image, std::vector<double> background, double threshold, bool const lineArt) {
+  VImage Trim(VImage image, std::vector<double> background, double threshold, bool const lineArt, int const margin) {
     if (image.width() < 3 && image.height() < 3) {
       throw VError("Image to trim must be at least 3x3 pixels");
     }
@@ -320,18 +320,36 @@ namespace sharp {
       if (widthA > 0 && heightA > 0) {
         if (width > 0 && height > 0) {
           // Combined bounding box (B)
-          int const leftB = std::min(left, leftA);
-          int const topB = std::min(top, topA);
-          int const widthB = std::max(left + width, leftA + widthA) - leftB;
-          int const heightB = std::max(top + height, topA + heightA) - topB;
+          int leftB = std::min(left, leftA);
+          int topB = std::min(top, topA);
+          int widthB = std::max(left + width, leftA + widthA) - leftB;
+          int heightB = std::max(top + height, topA + heightA) - topB;
+          if (margin > 0) {
+            leftB = std::max(0, leftB - margin);
+            topB = std::max(0, topB - margin);
+            widthB = std::min(image.width() - leftB, widthB + 2 * margin);
+            heightB = std::min(image.height() - topB, heightB + 2 * margin);
+          }
           return image.extract_area(leftB, topB, widthB, heightB);
         } else {
           // Use alpha only
+          if (margin > 0) {
+            leftA = std::max(0, leftA - margin);
+            topA = std::max(0, topA - margin);
+            widthA = std::min(image.width() - leftA, widthA + 2 * margin);
+            heightA = std::min(image.height() - topA, heightA + 2 * margin);
+          }
           return image.extract_area(leftA, topA, widthA, heightA);
         }
       }
     }
     if (width > 0 && height > 0) {
+      if (margin > 0) {
+        left = std::max(0, left - margin);
+        top = std::max(0, top - margin);
+        width = std::min(image.width() - left, width + 2 * margin);
+        height = std::min(image.height() - top, height + 2 * margin);
+      }
       return image.extract_area(left, top, width, height);
     }
     return image;

src/operations.h

@@ -82,7 +82,7 @@ namespace sharp {
   /*
     Trim an image
   */
-  VImage Trim(VImage image, std::vector<double> background, double threshold, bool const lineArt);
+  VImage Trim(VImage image, std::vector<double> background, double threshold, bool const lineArt, int const margin);
 
   /*
    * Linear adjustment (a * in + b)

src/pipeline.cc

@@ -153,7 +153,7 @@ class PipelineWorker : public Napi::AsyncWorker {
       if (baton->trimThreshold >= 0.0) {
         MultiPageUnsupported(nPages, "Trim");
         image = sharp::StaySequential(image);
-        image = sharp::Trim(image, baton->trimBackground, baton->trimThreshold, baton->trimLineArt);
+        image = sharp::Trim(image, baton->trimBackground, baton->trimThreshold, baton->trimLineArt, baton->trimMargin);
         baton->trimOffsetLeft = image.xoffset();
         baton->trimOffsetTop = image.yoffset();
       }
@@ -1637,6 +1637,7 @@ Napi::Value pipeline(const Napi::CallbackInfo& info) {
   baton->trimBackground = sharp::AttrAsVectorOfDouble(options, "trimBackground");
   baton->trimThreshold = sharp::AttrAsDouble(options, "trimThreshold");
   baton->trimLineArt = sharp::AttrAsBool(options, "trimLineArt");
+  baton->trimMargin = sharp::AttrAsUint32(options, "trimMargin");
   baton->gamma = sharp::AttrAsDouble(options, "gamma");
   baton->gammaOut = sharp::AttrAsDouble(options, "gammaOut");
   baton->linearA = sharp::AttrAsVectorOfDouble(options, "linearA");

src/pipeline.h

@@ -102,6 +102,7 @@ struct PipelineBaton {
   bool trimLineArt;
   int trimOffsetLeft;
   int trimOffsetTop;
+  int trimMargin;
   std::vector<double> linearA;
   std::vector<double> linearB;
   int dilateWidth;
@@ -286,6 +287,7 @@ struct PipelineBaton {
     trimLineArt(false),
     trimOffsetLeft(0),
     trimOffsetTop(0),
+    trimMargin(0),
     linearA{},
     linearB{},
     dilateWidth(0),

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);
+    });
+  });
 });