Add support for stand-alone, pre-resize, and post-resize extraction with a topOffset, leftOffset, width, and height.

index.js

@@ -19,6 +19,14 @@ var Sharp = function(input) {
     streamIn: false,
     sequentialRead: false,
     // resize options
+    topOffsetPre: -1,
+    leftOffsetPre: -1,
+    widthPre: -1,
+    heightPre: -1,
+    topOffsetPost: -1,
+    leftOffsetPost: -1,
+    widthPost: -1,
+    heightPost: -1,
     width: -1,
     height: -1,
     canvas: 'c',
@@ -102,6 +110,15 @@ Sharp.prototype.crop = function(gravity) {
   return this;
 };
 
+Sharp.prototype.extract = function(topOffset, leftOffset, width, height) {
+  var suffix = this.options.width === -1 && this.options.height === -1 ? 'Pre' : 'Post';
+  var values = arguments;
+  ['topOffset', 'leftOffset', 'width', 'height'].forEach(function(name, index) {
+    this.options[name + suffix] = values[index];
+  }.bind(this));
+  return this;
+};
+
 /*
   Deprecated embed* methods, to be removed in v0.8.0
 */

package.json

@@ -9,7 +9,8 @@
     "Juliano Julio <julianojulio@gmail.com>",
     "Daniel Gasienica <daniel@gasienica.ch>",
     "Julian Walker <julian@fiftythree.com>",
-    "Amit Pitaru <pitaru.amit@gmail.com>"
+    "Amit Pitaru <pitaru.amit@gmail.com>",
+    "Brandon Aaron <hello.brandon@aaron.sh>"
   ],
   "description": "High performance Node.js module to resize JPEG, PNG and WebP images using the libvips library",
   "scripts": {
@@ -30,6 +31,7 @@
     "thumbnail",
     "sharpen",
     "crop",
+    "extract",
     "embed",
     "libvips",
     "vips",

src/sharp.cc

@@ -25,6 +25,14 @@ struct resize_baton {
   std::string output_format;
   void* buffer_out;
   size_t buffer_out_len;
+  int topOffsetPre;
+  int leftOffsetPre;
+  int widthPre;
+  int heightPre;
+  int topOffsetPost;
+  int leftOffsetPost;
+  int widthPost;
+  int heightPost;
   int width;
   int height;
   Canvas canvas;
@@ -48,6 +56,8 @@ struct resize_baton {
     buffer_in_len(0),
     output_format(""),
     buffer_out_len(0),
+    topOffsetPre(-1),
+    topOffsetPost(-1),
     canvas(CROP),
     gravity(0),
     background{0.0, 0.0, 0.0, 255.0},
@@ -417,6 +427,17 @@ class ResizeWorker : public NanAsyncWorker {
       return resize_error(baton, hook);
     }
 
+    // Pre extraction
+    if (baton->topOffsetPre != -1) {
+      VipsImage *extractedPre = vips_image_new();
+      vips_object_local(hook, extractedPre);
+      if (vips_extract_area(image, &extractedPre, baton->leftOffsetPre, baton->topOffsetPre, baton->widthPre, baton->heightPre, NULL)) {
+        return resize_error(baton, hook);
+      }
+      g_object_unref(image);
+      image = extractedPre;
+    }
+
     // Get input image width and height
     int inputWidth = image->Xsize;
     int inputHeight = image->Ysize;
@@ -691,6 +712,17 @@ class ResizeWorker : public NanAsyncWorker {
       image = canvased;
     }
 
+    // Post extraction
+    if (baton->topOffsetPost != -1) {
+      VipsImage *extractedPost = vips_image_new();
+      vips_object_local(hook, extractedPost);
+      if (vips_extract_area(image, &extractedPost, baton->leftOffsetPost, baton->topOffsetPost, baton->widthPost, baton->heightPost, NULL)) {
+        return resize_error(baton, hook);
+      }
+      g_object_unref(image);
+      image = extractedPost;
+    }
+
     // Mild sharpen
     if (baton->sharpen) {
       VipsImage *sharpened = vips_image_new();
@@ -818,11 +850,21 @@ class ResizeWorker : public NanAsyncWorker {
       // Error
       argv[0] = NanNew<String>(baton->err.data(), baton->err.size());
     } else {
+      int width = baton->width;
+      int height = baton->height;
+      if (baton->topOffsetPre != -1 && (baton->width == -1 || baton->height == -1)) {
+        width = baton->widthPre;
+        height = baton->heightPre;
+      }
+      if (baton->topOffsetPost != -1) {
+        width = baton->widthPost;
+        height = baton->heightPost;
+      }
       // Info Object
       Local<Object> info = NanNew<Object>();
       info->Set(NanNew<String>("format"), NanNew<String>(baton->output_format));
-      info->Set(NanNew<String>("width"), NanNew<Number>(baton->width));
+      info->Set(NanNew<String>("width"), NanNew<Number>(width));
-      info->Set(NanNew<String>("height"), NanNew<Number>(baton->height));
+      info->Set(NanNew<String>("height"), NanNew<Number>(height));
 
       if (baton->buffer_out_len > 0) {
         // Buffer
@@ -847,6 +889,7 @@ class ResizeWorker : public NanAsyncWorker {
   resize_baton* baton;
 };
 
+
 /*
   resize(options, output, callback)
 */
@@ -866,6 +909,15 @@ NAN_METHOD(resize) {
     baton->buffer_in_len = Buffer::Length(buffer);
     baton->buffer_in = Buffer::Data(buffer);
   }
+  // Extract image options
+  baton->topOffsetPre = options->Get(NanNew<String>("topOffsetPre"))->Int32Value();
+  baton->leftOffsetPre = options->Get(NanNew<String>("leftOffsetPre"))->Int32Value();
+  baton->widthPre = options->Get(NanNew<String>("widthPre"))->Int32Value();
+  baton->heightPre = options->Get(NanNew<String>("heightPre"))->Int32Value();
+  baton->topOffsetPost = options->Get(NanNew<String>("topOffsetPost"))->Int32Value();
+  baton->leftOffsetPost = options->Get(NanNew<String>("leftOffsetPost"))->Int32Value();
+  baton->widthPost = options->Get(NanNew<String>("widthPost"))->Int32Value();
+  baton->heightPost = options->Get(NanNew<String>("heightPost"))->Int32Value();
   // Output image dimensions
   baton->width = options->Get(NanNew<String>("width"))->Int32Value();
   baton->height = options->Get(NanNew<String>("height"))->Int32Value();

tests/unit.js

@@ -563,6 +563,69 @@ async.series([
       done();
     });
   },
+  // Extract jpg
+  function(done) {
+    sharp(inputJpg).extract(2,2,20,20).toFile(path.join(fixturesPath, 'output.extract.jpg'), function(err, info) {
+      if (err) throw err;
+      assert.strictEqual(20, info.width);
+      assert.strictEqual(20, info.height);
+      done();
+    });
+  },
+  // Extract png
+  function(done) {
+    sharp(inputPng).extract(300,200,400,200).toFile(path.join(fixturesPath, 'output.extract.png'), function(err, info) {
+      if (err) throw err;
+      assert.strictEqual(400, info.width);
+      assert.strictEqual(200, info.height);
+      done();
+    });
+  },
+  // Extract webp
+  function(done) {
+    sharp(inputWebP).extract(50, 100, 125, 200).toFile(path.join(fixturesPath, 'output.extract.webp'), function(err, info) {
+      if (err) throw err;
+      assert.strictEqual(125, info.width);
+      assert.strictEqual(200, info.height);
+      done();
+    });
+  },
+  // Extract tiff
+  function(done) {
+    sharp(inputTiff).extract(63, 34, 341, 529).toFile(path.join(fixturesPath, 'output.extract.tiff'), function(err, info) {
+      if (err) throw err;
+      assert.strictEqual(341, info.width);
+      assert.strictEqual(529, info.height);
+      done();
+    });
+  },
+  // Extract before resize
+  function(done) {
+    sharp(inputJpg).extract(10, 10, 10, 500, 500).resize(100, 100).toFile(path.join(fixturesPath, 'output.extract.resize.jpg'), function(err, info) {
+      if (err) throw err;
+      assert.strictEqual(100, info.width);
+      assert.strictEqual(100, info.height);
+      done();
+    });
+  },
+  // Extract after resize and crop
+  function(done) {
+    sharp(inputJpg).resize(500, 500).crop(sharp.gravity.north).extract(10, 10, 100, 100).toFile(path.join(fixturesPath, 'output.resize.crop.extract.jpg'), function(err, info) {
+      if (err) throw err;
+      assert.strictEqual(100, info.width);
+      assert.strictEqual(100, info.height);
+      done();
+    });
+  },
+  // Extract before and after resize and crop
+  function(done) {
+    sharp(inputJpg).extract(0, 0, 700, 700).resize(500, 500).crop(sharp.gravity.north).extract(10, 10, 100, 100).toFile(path.join(fixturesPath, 'output.extract.resize.crop.extract.jpg'), function(err, info) {
+      if (err) throw err;
+      assert.strictEqual(100, info.width);
+      assert.strictEqual(100, info.height);
+      done();
+    });
+  },
   // Keeps Metadata after a resize
   function(done) {
       sharp(inputJpgWithExif).resize(320, 240).withMetadata().toBuffer(function(err, buffer) {