Add support for auto-scaling of width and height

README.md

@@ -31,7 +31,7 @@ Under the hood you'll find the blazingly fast [libvips](https://github.com/jcupi
 	git clone https://github.com/jcupitt/libvips.git
 	cd libvips
 	./bootstrap.sh
-	./configure --enable-debug=no --enable-cxx=no --without-magick --without-lcms --without-OpenEXR --without-openslide --without-matio --without-cfitsio --without-pangoft2 --without-zip --without-libexif --without-python
+	./configure --enable-debug=no
 	make
 	sudo make install
 	sudo ldconfig
@@ -52,9 +52,9 @@ Scale and crop to `width` x `height` calling `callback` when complete.
 
 `output` can either be a filename String or one of `sharp.buffer.jpeg`, `sharp.buffer.png` or `sharp.buffer.webp` to pass a Buffer containing JPEG, PNG or WebP image data to `callback`.
 
-`width` is the Number of pixels wide the resultant image should be.
+`width` is the Number of pixels wide the resultant image should be. Use a value of -1 to auto-scale the width to match the height.
 
-`height` is the Number of pixels high the resultant image should be.
+`height` is the Number of pixels high the resultant image should be. Use a value of -1 to auto-scale the height to match the width.
 
 `options` is optional, and can contain one or more of:
 
@@ -78,20 +78,20 @@ sharp.resize("input.jpg", "output.jpg", 300, 200, function(err) {
 ```
 
 ```javascript
-sharp.resize("input.jpg", sharp.buffer.jpeg, 300, 200, {progressive: true}, function(err, buffer) {
+sharp.resize("input.jpg", sharp.buffer.jpeg, -1, 200, {progressive: true}, function(err, buffer) {
   if (err) {
     throw err;
   }
-  // buffer contains progressive JPEG image data
+  // buffer contains progressive JPEG image data, 200 pixels high
 });
 ```
 
 ```javascript
-sharp.resize("input.webp", sharp.buffer.png, 300, 200, {sharpen: true}, function(err, buffer) {
+sharp.resize("input.webp", sharp.buffer.png, 300, -1, {sharpen: true}, function(err, buffer) {
   if (err) {
     throw err;
   }
-  // buffer contains sharpened PNG image data (converted from JPEG)
+  // buffer contains sharpened PNG image data (converted from JPEG), 300 pixels wide
 });
 ```
 

index.js

@@ -42,6 +42,10 @@ module.exports.resize = function(input, output, width, height, options, callback
     callback("Invalid height " + height);
     return;
   }
+  if (outWidth < 1 && outHeight < 1) {
+    callback("Width and/or height required");
+    return;
+  }
   var canvas = options.canvas || "c";
   if (canvas.length !== 1 || "cwb".indexOf(canvas) === -1) {
     callback("Invalid canvas " + canvas);
@@ -50,15 +54,16 @@ module.exports.resize = function(input, output, width, height, options, callback
   var sharpen = !!options.sharpen;
   var progessive = !!options.progessive;
   var sequentialRead = !!options.sequentialRead;
-  sharp.resize(options.inFile, options.inBuffer, output, width, height, canvas, sharpen, progessive, sequentialRead, callback);
+  sharp.resize(options.inFile, options.inBuffer, output, outWidth, outHeight, canvas, sharpen, progessive, sequentialRead, callback);
 };
 
 module.exports.cache = function(limit) {
+  "use strict";
   if (Number.isNaN(limit)) {
     limit = null;
   }
   return sharp.cache(limit);
-}
+};
 
 /* Deprecated v0.0.x methods */
 module.exports.crop = function(input, output, width, height, sharpen, callback) {

package.json

@@ -1,10 +1,10 @@
 {
   "name": "sharp",
-  "version": "0.1.7",
+  "version": "0.1.8",
   "author": "Lovell Fuller",
   "description": "High performance module to resize JPEG, PNG, WebP and TIFF images using the libvips image processing library",
   "scripts": {
-    "test": "node tests/perf.js"
+    "test": "node tests/unit && node tests/perf"
   },
   "main": "index.js",
   "repository": {

src/sharp.cc

@@ -119,7 +119,24 @@ void resize_async(uv_work_t *work) {
 
   double xfactor = static_cast<double>(in->Xsize) / std::max(baton->width, 1);
   double yfactor = static_cast<double>(in->Ysize) / std::max(baton->height, 1);
-  double factor = baton->crop ? std::min(xfactor, yfactor) : std::max(xfactor, yfactor);
+  double factor;
+  if (baton->width > 0 && baton->height > 0) {
+    // Fixed width and height
+    factor = baton->crop ? std::min(xfactor, yfactor) : std::max(xfactor, yfactor);
+  } else if (baton->width > 0) {
+    // Fixed width, auto height
+    factor = xfactor;
+    baton->height = floor(in->Ysize * factor);
+  } else if (baton->height > 0) {
+    // Fixed height, auto width
+    factor = yfactor;
+    baton->width = floor(in->Xsize * factor);
+  } else {
+    resize_error(baton, in);
+    (baton->err).append("Width and/or height required");
+    return;
+  }
+
   factor = std::max(factor, 1.0);
   int shrink = floor(factor);
   double residual = shrink / factor;

tests/random.js

@@ -15,7 +15,7 @@ var max = 960;
 
 var randomDimension = function() {
   return Math.random() * (max - min) + min;
-}
+};
 
 new Benchmark.Suite("random").add("imagemagick", {
 	defer: true,

tests/unit.js

@@ -0,0 +1,34 @@
+var sharp = require("../index");
+var imagemagick = require("imagemagick");
+var assert = require("assert");
+
+var inputJpg = __dirname + "/2569067123_aca715a2ee_o.jpg"; // http://www.flickr.com/photos/grizdave/2569067123/
+var outputJpg = __dirname + "/output.jpg";
+
+sharp.resize(inputJpg, outputJpg, 320, 240, function(err) {
+  if (err) throw err;
+  imagemagick.identify(outputJpg, function(err, features) {
+    if (err) throw err;
+    assert.strictEqual(320, features.width);
+    assert.strictEqual(240, features.height);
+
+    sharp.resize(inputJpg, outputJpg, 320, -1, function(err) {
+      if (err) throw err;
+      imagemagick.identify(outputJpg, function(err, features) {
+        if (err) throw err;
+        assert.strictEqual(320, features.width);
+        assert.strictEqual(262, features.height);
+      });
+
+      sharp.resize(inputJpg, outputJpg, -1, 320, function(err) {
+        if (err) throw err;
+        imagemagick.identify(outputJpg, function(err, features) {
+          if (err) throw err;
+          assert.strictEqual(392, features.width);
+          assert.strictEqual(320, features.height);
+        });
+      });
+
+    });
+  });
+});