Add support to extend for extendWith, allows copy/mirror/repeat (#3556)

lib/constructor.js

@@ -197,6 +197,7 @@ const Sharp = function (input, options) {
     extendLeft: 0,
     extendRight: 0,
     extendBackground: [0, 0, 0, 255],
+    extendWith: 'background',
     withoutEnlargement: false,
     withoutReduction: false,
     affineMatrix: [],

lib/index.d.ts

@@ -755,7 +755,7 @@ declare namespace sharp {
         resize(options: ResizeOptions): Sharp;
 
         /**
-         * Extends/pads the edges of the image with the provided background colour.
+         * Extends/pads the edges of the image with either the provided background colour or pixels derived from the image.
          * This operation will always occur after resizing and extraction, if any.
          * @param extend single pixel count to add to all edges or an Object with per-edge counts
          * @throws {Error} Invalid parameters
@@ -1245,6 +1245,8 @@ declare namespace sharp {
         sigma?: number | undefined;
     }
 
+    type ExtendWith = 'background' | 'copy' | 'repeat' | 'mirror';
+
     interface ExtendOptions {
         /** single pixel count to top edge (optional, default 0) */
         top?: number | undefined;
@@ -1256,6 +1258,8 @@ declare namespace sharp {
         right?: number | undefined;
         /** background colour, parsed by the color module, defaults to black without transparency. (optional, default {r:0,g:0,b:0,alpha:1}) */
         background?: Color | undefined;
+        /** how the extension is done, one of: "background", "copy", "repeat", "mirror" (optional, default `'background'`) */
+        extendWith?: ExtendWith | undefined;
     }
 
     interface TrimOptions {

lib/resize.js

@@ -36,6 +36,18 @@ const position = {
   'left top': 8
 };
 
+/**
+ * How to extend the image.
+ * @member
+ * @private
+ */
+const extendWith = {
+  background: 'background',
+  copy: 'copy',
+  repeat: 'repeat',
+  mirror: 'mirror'
+};
+
 /**
  * Strategies for automagic cover behaviour.
  * @member
@@ -393,6 +405,13 @@ function extend (extend) {
       }
     }
     this._setBackgroundColourOption('extendBackground', extend.background);
+    if (is.defined(extend.extendWith)) {
+      if (is.string(extendWith[extend.extendWith])) {
+        this.options.extendWith = extendWith[extend.extendWith];
+      } else {
+        throw is.invalidParameterError('extendWith', 'valid value', extend.extendWith);
+      }
+    }
   } else {
     throw is.invalidParameterError('extend', 'integer or object', extend);
   }

src/operations.cc

@@ -395,11 +395,11 @@ namespace sharp {
    * Split into frames, embed each frame, reassemble, and update pageHeight.
    */
   VImage EmbedMultiPage(VImage image, int left, int top, int width, int height,
-                        std::vector<double> background, int nPages, int *pageHeight) {
+                        VipsExtend extendWith, std::vector<double> background, int nPages, int *pageHeight) {
     if (top == 0 && height == *pageHeight) {
       // Fast path; no need to adjust the height of the multi-page image
       return image.embed(left, 0, width, image.height(), VImage::option()
-        ->set("extend", VIPS_EXTEND_BACKGROUND)
+        ->set("extend", extendWith)
         ->set("background", background));
     } else if (left == 0 && width == image.width()) {
       // Fast path; no need to adjust the width of the multi-page image
@@ -411,7 +411,7 @@ namespace sharp {
 
       // Do the embed on the wide image
       image = image.embed(0, top, image.width(), height, VImage::option()
-        ->set("extend", VIPS_EXTEND_BACKGROUND)
+        ->set("extend", extendWith)
         ->set("background", background));
 
       // Split the wide image into frames
@@ -441,7 +441,7 @@ namespace sharp {
       // Embed each frame in the target size
       for (int i = 0; i < nPages; i++) {
         pages[i] = pages[i].embed(left, top, width, height, VImage::option()
-          ->set("extend", VIPS_EXTEND_BACKGROUND)
+          ->set("extend", extendWith)
           ->set("background", background));
       }
 

src/operations.h

@@ -124,7 +124,7 @@ namespace sharp {
    * Split into frames, embed each frame, reassemble, and update pageHeight.
    */
   VImage EmbedMultiPage(VImage image, int left, int top, int width, int height,
-                        std::vector<double> background, int nPages, int *pageHeight);
+                        VipsExtend extendWith, std::vector<double> background, int nPages, int *pageHeight);
 
 }  // namespace sharp
 

src/pipeline.cc

@@ -441,7 +441,7 @@ class PipelineWorker : public Napi::AsyncWorker {
 
           image = nPages > 1
             ? sharp::EmbedMultiPage(image,
-                left, top, width, height, background, nPages, &targetPageHeight)
+                left, top, width, height, VIPS_EXTEND_BACKGROUND, background, nPages, &targetPageHeight)
             : image.embed(left, top, width, height, VImage::option()
               ->set("extend", VIPS_EXTEND_BACKGROUND)
               ->set("background", background));
@@ -532,18 +532,29 @@ class PipelineWorker : public Napi::AsyncWorker {
 
       // Extend edges
       if (baton->extendTop > 0 || baton->extendBottom > 0 || baton->extendLeft > 0 || baton->extendRight > 0) {
-        std::vector<double> background;
-        std::tie(image, background) = sharp::ApplyAlpha(image, baton->extendBackground, shouldPremultiplyAlpha);
-
         // Embed
         baton->width = image.width() + baton->extendLeft + baton->extendRight;
         baton->height = (nPages > 1 ? targetPageHeight : image.height()) + baton->extendTop + baton->extendBottom;
 
+        if (baton->extendWith == VIPS_EXTEND_BACKGROUND) {
+          std::vector<double> background;
+          std::tie(image, background) = sharp::ApplyAlpha(image, baton->extendBackground, shouldPremultiplyAlpha);
+
           image = nPages > 1
             ? sharp::EmbedMultiPage(image,
-              baton->extendLeft, baton->extendTop, baton->width, baton->height, background, nPages, &targetPageHeight)
+                baton->extendLeft, baton->extendTop, baton->width, baton->height,
+                baton->extendWith, background, nPages, &targetPageHeight)
             : image.embed(baton->extendLeft, baton->extendTop, baton->width, baton->height,
-              VImage::option()->set("extend", VIPS_EXTEND_BACKGROUND)->set("background", background));
+                VImage::option()->set("extend", baton->extendWith)->set("background", background));
+        } else {
+          std::vector<double> ignoredBackground(1);
+          image = nPages > 1
+            ? sharp::EmbedMultiPage(image,
+                baton->extendLeft, baton->extendTop, baton->width, baton->height,
+                baton->extendWith, ignoredBackground, nPages, &targetPageHeight)
+            : image.embed(baton->extendLeft, baton->extendTop, baton->width, baton->height,
+                VImage::option()->set("extend", baton->extendWith));
+        }
       }
       // Median - must happen before blurring, due to the utility of blurring after thresholding
       if (baton->medianSize > 0) {
@@ -1500,6 +1511,7 @@ Napi::Value pipeline(const Napi::CallbackInfo& info) {
   baton->extendLeft = sharp::AttrAsInt32(options, "extendLeft");
   baton->extendRight = sharp::AttrAsInt32(options, "extendRight");
   baton->extendBackground = sharp::AttrAsVectorOfDouble(options, "extendBackground");
+  baton->extendWith = sharp::AttrAsEnum<VipsExtend>(options, "extendWith", VIPS_TYPE_EXTEND);
   baton->extractChannel = sharp::AttrAsInt32(options, "extractChannel");
   baton->affineMatrix = sharp::AttrAsVectorOfDouble(options, "affineMatrix");
   baton->affineBackground = sharp::AttrAsVectorOfDouble(options, "affineBackground");

src/pipeline.h

@@ -125,6 +125,7 @@ struct PipelineBaton {
   int extendLeft;
   int extendRight;
   std::vector<double> extendBackground;
+  VipsExtend extendWith;
   bool withoutEnlargement;
   bool withoutReduction;
   std::vector<double> affineMatrix;
@@ -286,6 +287,7 @@ struct PipelineBaton {
     extendLeft(0),
     extendRight(0),
     extendBackground{ 0.0, 0.0, 0.0, 255.0 },
+    extendWith(VIPS_EXTEND_BACKGROUND),
     withoutEnlargement(false),
     withoutReduction(false),
     affineMatrix{ 1.0, 0.0, 0.0, 1.0 },

test/unit/extend.js

@@ -32,10 +32,30 @@ describe('Extend', function () {
     });
   });
 
-  it('extend all sides equally with RGB', function (done) {
+  ['background', 'copy', 'mirror', 'repeat'].forEach(extendWith => {
+    it(`extends all sides with animated WebP (${extendWith})`, function (done) {
+      sharp(fixtures.inputWebPAnimated, { pages: -1 })
+        .resize(120)
+        .extend({
+          extendWith: extendWith,
+          top: 40,
+          bottom: 40,
+          left: 40,
+          right: 40
+        })
+        .toBuffer(function (err, data, info) {
+          if (err) throw err;
+          assert.strictEqual(200, info.width);
+          assert.strictEqual(200 * 9, info.height);
+          fixtures.assertSimilar(fixtures.expected(`extend-equal-${extendWith}.webp`), data, done);
+        });
+    });
+
+    it(`extend all sides equally with RGB (${extendWith})`, function (done) {
       sharp(fixtures.inputJpg)
         .resize(120)
         .extend({
+          extendWith: extendWith,
           top: 10,
           bottom: 10,
           left: 10,
@@ -46,14 +66,15 @@ describe('Extend', function () {
           if (err) throw err;
           assert.strictEqual(140, info.width);
           assert.strictEqual(118, info.height);
-        fixtures.assertSimilar(fixtures.expected('extend-equal.jpg'), data, done);
+          fixtures.assertSimilar(fixtures.expected(`extend-equal-${extendWith}.jpg`), data, done);
         });
     });
 
-  it('extend sides unequally with RGBA', function (done) {
+    it(`extend sides unequally with RGBA (${extendWith})`, function (done) {
       sharp(fixtures.inputPngWithTransparency16bit)
         .resize(120)
         .extend({
+          extendWith: extendWith,
           top: 50,
           left: 10,
           right: 35,
@@ -63,7 +84,29 @@ describe('Extend', function () {
           if (err) throw err;
           assert.strictEqual(165, info.width);
           assert.strictEqual(170, info.height);
-        fixtures.assertSimilar(fixtures.expected('extend-unequal.png'), data, done);
+          fixtures.assertSimilar(fixtures.expected(`extend-unequal-${extendWith}.png`), data, done);
+        });
+    });
+
+    it(`PNG with 2 channels (${extendWith})`, function (done) {
+      sharp(fixtures.inputPngWithGreyAlpha)
+        .extend({
+          extendWith: extendWith,
+          top: 50,
+          bottom: 50,
+          left: 80,
+          right: 80,
+          background: 'transparent'
+        })
+        .toBuffer(function (err, data, info) {
+          if (err) throw err;
+          assert.strictEqual(true, data.length > 0);
+          assert.strictEqual('png', info.format);
+          assert.strictEqual(560, info.width);
+          assert.strictEqual(400, info.height);
+          assert.strictEqual(4, info.channels);
+          fixtures.assertSimilar(fixtures.expected(`extend-2channel-${extendWith}.png`), data, done);
+        });
     });
   });
 
@@ -101,6 +144,12 @@ describe('Extend', function () {
       /Expected positive integer for right but received \[object Object\] of type object/
     );
   });
+  it('invalid extendWith fails', () => {
+    assert.throws(
+      () => sharp().extend({ extendWith: 'invalid-value' }),
+      /Expected valid value for extendWith but received invalid-value of type string/
+    );
+  });
   it('can set all edges apart from right', () => {
     assert.doesNotThrow(() => sharp().extend({ top: 1, left: 2, bottom: 3 }));
   });
@@ -121,24 +170,6 @@ describe('Extend', function () {
       });
   });
 
-  it('PNG with 2 channels', function (done) {
-    sharp(fixtures.inputPngWithGreyAlpha)
-      .extend({
-        bottom: 20,
-        right: 20,
-        background: 'transparent'
-      })
-      .toBuffer(function (err, data, info) {
-        if (err) throw err;
-        assert.strictEqual(true, data.length > 0);
-        assert.strictEqual('png', info.format);
-        assert.strictEqual(420, info.width);
-        assert.strictEqual(320, info.height);
-        assert.strictEqual(4, info.channels);
-        fixtures.assertSimilar(fixtures.expected('extend-2channel.png'), data, done);
-      });
-  });
-
   it('Premultiply background when compositing', async () => {
     const background = { r: 191, g: 25, b: 66, alpha: 0.8 };
     const data = await sharp({