Resize images with preserve aspect ratio

atom/common/api/atom_api_native_image.cc

@@ -284,15 +284,32 @@ gfx::Size NativeImage::GetSize() {
   return image_.Size();
 }
 
+float NativeImage::GetAspectRatio() {
+  gfx::Size size = GetSize();
+  if (size.IsEmpty())
+    return 1.f;
+  else
+    return static_cast<float>(size.width()) / static_cast<float>(size.height());
+}
+
 mate::Handle<NativeImage> NativeImage::Resize(
     v8::Isolate* isolate, const base::DictionaryValue& options) {
   gfx::Size size = GetSize();
   int width = size.width();
   int height = size.height();
-  options.GetInteger("width", &width);
-  options.GetInteger("height", &height);
-  size.set_width(width);
-  size.set_height(height);
+  bool width_set = options.GetInteger("width", &width);
+  bool height_set = options.GetInteger("height", &height);
+  size.SetSize(width, height);
+
+  if (width_set && !height_set) {
+    // Scale height to preserve original aspect ratio
+    size.set_height(width);
+    size = gfx::ScaleToRoundedSize(size, 1.f, 1.f / GetAspectRatio());
+  } else if (height_set && !width_set) {
+    // Scale width to preserve original aspect ratio
+    size.set_width(height);
+    size = gfx::ScaleToRoundedSize(size, GetAspectRatio(), 1.f);
+  }
 
   skia::ImageOperations::ResizeMethod method =
       skia::ImageOperations::ResizeMethod::RESIZE_BEST;
@@ -420,6 +437,7 @@ void NativeImage::BuildPrototype(
       .SetMethod("isTemplateImage", &NativeImage::IsTemplateImage)
       .SetMethod("resize", &NativeImage::Resize)
       .SetMethod("crop", &NativeImage::Crop)
+      .SetMethod("getAspectRatio", &NativeImage::GetAspectRatio)
       // TODO(kevinsawicki): Remove in 2.0, deprecate before then with warnings
       .SetMethod("toPng", &NativeImage::ToPNG)
       .SetMethod("toJpeg", &NativeImage::ToJPEG);

atom/common/api/atom_api_native_image.h

@@ -84,6 +84,7 @@ class NativeImage : public mate::Wrappable<NativeImage> {
   std::string ToDataURL();
   bool IsEmpty();
   gfx::Size GetSize();
+  float GetAspectRatio();
 
   // Mark the image as template image.
   void SetTemplateImage(bool setAsTemplate);

docs/api/native-image.md

@@ -239,4 +239,11 @@ Returns `NativeImage` - The cropped image.
 
 Returns `NativeImage` - The resized image.
 
+If only the `height` or the `width` are specified then the current aspect ratio
+will be preserved in the resized image.
+
+#### `image.getAspectRatio()`
+
+Returns `Float` - The image's aspect ratio.
+
 [buffer]: https://nodejs.org/api/buffer.html#buffer_class_buffer

spec/api-native-image-spec.js

@@ -98,9 +98,12 @@ describe('nativeImage module', () => {
     it('returns a resized image', () => {
       const image = nativeImage.createFromPath(path.join(__dirname, 'fixtures', 'assets', 'logo.png'))
       assert.deepEqual(image.resize({}).getSize(), {width: 538, height: 190})
-      assert.deepEqual(image.resize({width: 400}).getSize(), {width: 400, height: 190})
-      assert.deepEqual(image.resize({height: 123}).getSize(), {width: 538, height: 123})
+      assert.deepEqual(image.resize({width: 269}).getSize(), {width: 269, height: 95})
+      assert.deepEqual(image.resize({width: 600}).getSize(), {width: 600, height: 212})
+      assert.deepEqual(image.resize({height: 95}).getSize(), {width: 269, height: 95})
+      assert.deepEqual(image.resize({height: 200}).getSize(), {width: 566, height: 200})
       assert.deepEqual(image.resize({width: 80, height: 65}).getSize(), {width: 80, height: 65})
+      assert.deepEqual(image.resize({width: 600, height: 200}).getSize(), {width: 600, height: 200})
       assert.deepEqual(image.resize({width: 0, height: 0}).getSize(), {width: 0, height: 0})
       assert.deepEqual(image.resize({width: -1, height: -1}).getSize(), {width: 0, height: 0})
     })