Add support for multiple DPI images, fixes #541.

atom/common/native_mate_converters/image_converter.cc

@@ -5,6 +5,7 @@
 #include "atom/common/native_mate_converters/image_converter.h"
 
 #include <string>
+#include <vector>
 
 #include "atom/common/native_mate_converters/file_path_converter.h"
 #include "base/file_util.h"
@@ -18,12 +19,83 @@ namespace mate {
 
 namespace {
 
-ui::ScaleFactor GetScaleFactorFromFileName(const base::FilePath& path) {
+struct ScaleFactorPair {
+  const char* name;
+  float scale;
+};
+
+ScaleFactorPair kScaleFactorPairs[] = {
+  // The "@2x" is put as first one to make scale matching faster.
+  { "@2x"    , 2.0f },
+  { "@3x"    , 3.0f },
+  { "@1x"    , 1.0f },
+  { "@1.25x" , 1.25f },
+  { "@1.33x" , 1.33f },
+  { "@1.4x"  , 1.4f },
+  { "@1.5x"  , 1.5f },
+  { "@1.8x"  , 1.8f },
+  { "@2.5x"  , 2.5f },
+};
+
+float GetScaleFactorFromPath(const base::FilePath& path) {
   std::string filename(path.BaseName().RemoveExtension().AsUTF8Unsafe());
-  if (EndsWith(filename, "@2x", true))
+
-    return ui::SCALE_FACTOR_200P;
+  // There is no scale info in the file path.
-  else
+  if (!EndsWith(filename, "x", true))
-    return ui::SCALE_FACTOR_100P;
+    return 1.0f;
+
+  // We don't try to convert string to float here because it is very very
+  // expensive.
+  for (unsigned i = 0; i < arraysize(kScaleFactorPairs); ++i) {
+    if (EndsWith(filename, kScaleFactorPairs[i].name, true))
+      return kScaleFactorPairs[i].scale;
+  }
+
+  return 1.0f;
+}
+
+void AppendIfExists(std::vector<base::FilePath>* paths,
+                    const base::FilePath& path) {
+  if (base::PathExists(path))
+    paths->push_back(path);
+}
+
+void PopulatePossibleFilePaths(std::vector<base::FilePath>* paths,
+                               const base::FilePath& path) {
+  AppendIfExists(paths, path);
+
+  std::string filename(path.BaseName().RemoveExtension().AsUTF8Unsafe());
+  if (MatchPattern(filename, "*@*x"))
+    return;
+
+  for (unsigned i = 0; i < arraysize(kScaleFactorPairs); ++i)
+    AppendIfExists(paths,
+                   path.InsertBeforeExtensionASCII(kScaleFactorPairs[i].name));
+}
+
+bool AddImageSkiaRepFromPath(gfx::ImageSkia* image,
+                             const base::FilePath& path) {
+  std::string file_contents;
+  if (!base::ReadFileToString(path, &file_contents))
+    return false;
+
+  const unsigned char* data =
+      reinterpret_cast<const unsigned char*>(file_contents.data());
+  size_t size = file_contents.size();
+  scoped_ptr<SkBitmap> decoded(new SkBitmap());
+
+  // Try PNG first.
+  if (!gfx::PNGCodec::Decode(data, size, decoded.get()))
+    // Try JPEG.
+    decoded.reset(gfx::JPEGCodec::Decode(data, size));
+
+  if (decoded) {
+    image->AddRepresentation(gfx::ImageSkiaRep(
+        *decoded.release(), GetScaleFactorFromPath(path)));
+    return true;
+  }
+
+  return false;
 }
 
 }  // namespace
@@ -33,25 +105,16 @@ bool Converter<gfx::ImageSkia>::FromV8(v8::Isolate* isolate,
                                        gfx::ImageSkia* out) {
   base::FilePath path;
   if (Converter<base::FilePath>::FromV8(isolate, val, &path)) {
-    std::string file_contents;
+    std::vector<base::FilePath> paths;
-    if (!base::ReadFileToString(path, &file_contents))
+    PopulatePossibleFilePaths(&paths, path);
+    if (paths.empty())
       return false;
 
-    const unsigned char* data =
+    for (size_t i = 0; i < paths.size(); ++i) {
-        reinterpret_cast<const unsigned char*>(file_contents.data());
+      if (!AddImageSkiaRepFromPath(out, paths[i]))
-    size_t size = file_contents.size();
+        return false;
-    scoped_ptr<SkBitmap> decoded(new SkBitmap());
-
-    // Try PNG first.
-    if (!gfx::PNGCodec::Decode(data, size, decoded.get()))
-      // Try JPEG.
-      decoded.reset(gfx::JPEGCodec::Decode(data, size));
-
-    if (decoded) {
-      *out = gfx::ImageSkia(gfx::ImageSkiaRep(*decoded.release(),
-                            GetScaleFactorFromFileName(path)));
-      return true;
     }
+    return true;
   }
 
   return false;

docs/api/image.md

@@ -7,7 +7,7 @@ For example when creating tray or setting window's icon, you can pass image's
 file path as `String` to represent an image:
 
 ```javascript
-var appIcon = new Tray('/Users/somebody/images/icon@2x.png');
+var appIcon = new Tray('/Users/somebody/images/icon.png');
 var window = new BrowserWindow({icon: '/Users/somebody/images/window.png'});
 ```
 
@@ -23,3 +23,32 @@ file name's base name to mark it as a high resolution image.
 For example if `icon.png` is a normal image that has standard resolution, the
 `icon@2x.png` would be treated as a high resolution image that has double DPI
 dense.
+
+If you want to support displays with different DPI denses at the same time, you
+can put images with different sizes in the same folder, and use the filename
+without DPI suffixes, like this:
+
+```text
+images/
+├── icon.png
+├── icon@2x.png
+└── icon@3x.png
+```
+
+
+```javascript
+var appIcon = new Tray('/Users/somebody/images/icon.png');
+```
+
+Following suffixes as DPI denses are also supported:
+
+* `@1x`
+* `@1.25x`
+* `@1.33x`
+* `@1.4x`
+* `@1.5x`
+* `@1.8x`
+* `@2x`
+* `@2.5x`
+* `@3x`
+