FileImage (#6853)

packages/flutter/lib/src/services/image_provider.dart

@@ -3,6 +3,7 @@
 // found in the LICENSE file.
 
 import 'dart:async';
+import 'dart:io' show File;
 import 'dart:ui' show Size, Locale, hashValues;
 import 'dart:ui' as ui show Image;
 import 'dart:typed_data';
@@ -370,6 +371,68 @@ class NetworkImage extends ImageProvider<NetworkImage> {
   String toString() => '$runtimeType("$url", scale: $scale)';
 }
 
+/// Decodes the given [File] object as an image, associating it with the given
+/// scale.
+class FileImage extends ImageProvider<FileImage> {
+  /// Creates an object that decodes a [File] as an image.
+  ///
+  /// The arguments must not be null.
+  const FileImage(this.file, { this.scale: 1.0 });
+
+  /// The file to decode into an image.
+  final File file;
+
+  /// The scale to place in the [ImageInfo] object of the image.
+  final double scale;
+
+  @override
+  Future<FileImage> obtainKey(ImageConfiguration configuration) {
+    return new SynchronousFuture<FileImage>(this);
+  }
+
+  @override
+  ImageStreamCompleter load(FileImage key) {
+    return new OneFrameImageStreamCompleter(
+      _loadAsync(key),
+      informationCollector: (StringBuffer information) {
+        information.writeln('Path: ${file?.path}');
+      }
+    );
+  }
+
+  Future<ImageInfo> _loadAsync(FileImage key) async {
+    assert(key == this);
+
+    Uint8List bytes = await file.readAsBytes();
+    if (bytes.lengthInBytes == 0)
+      return null;
+
+    final ui.Image image = await decodeImageFromList(bytes);
+    if (image == null)
+      return null;
+
+    return new ImageInfo(
+      image: image,
+      scale: key.scale,
+    );
+  }
+
+  @override
+  bool operator ==(dynamic other) {
+    if (other.runtimeType != runtimeType)
+      return false;
+    final FileImage typedOther = other;
+    return file?.path == file?.path
+        && scale == typedOther.scale;
+  }
+
+  @override
+  int get hashCode => hashValues(file?.path, scale);
+
+  @override
+  String toString() => '$runtimeType("${file?.path}", scale: $scale)';
+}
+
 /// Fetches an image from an [AssetBundle], associating it with the given scale.
 ///
 /// This implementation requires an explicit final [name] and [scale] on

packages/flutter/lib/src/widgets/image.dart

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-import 'dart:io' show Platform;
+import 'dart:io' show File, Platform;
 
 import 'package:flutter/services.dart';
 import 'package:meta/meta.dart';
@@ -14,7 +14,8 @@ import 'media_query.dart';
 export 'package:flutter/services.dart' show
     AssetImage,
     ExactAssetImage,
-    NetworkImage;
+    NetworkImage,
+    FileImage;
 
 /// Creates an [ImageConfiguration] based on the given [BuildContext] (and
 /// optionally size).
@@ -37,9 +38,10 @@ ImageConfiguration createLocalImageConfiguration(BuildContext context, { Size si
 /// specified:
 ///
 /// * [new Image], for obtaining an image from an [ImageProvider].
-/// * [new Image.network], for obtaining an image from a URL.
 /// * [new Image.asset], for obtaining an image from an [AssetBundle]
 ///   using a key.
+/// * [new Image.network], for obtaining an image from a URL.
+/// * [new Image.file], for obtaining an image from a [File].
 ///
 /// To automatically perform pixel-density-aware asset resolution, specify the
 /// image using an [AssetImage] and make sure that a [MaterialApp], [WidgetsApp],
@@ -90,6 +92,26 @@ class Image extends StatefulWidget {
   }) : image = new NetworkImage(src, scale: scale),
        super(key: key);
 
+  /// Creates a widget that displays an [ImageStream] obtained from a [File].
+  ///
+  /// The [file], [scale], and [repeat] arguments must not be null.
+  ///
+  /// On Android, this may require the
+  /// `android.permission.READ_EXTERNAL_STORAGE` permission.
+  Image.file(File file, {
+    Key key,
+    double scale: 1.0,
+    this.width,
+    this.height,
+    this.color,
+    this.fit,
+    this.alignment,
+    this.repeat: ImageRepeat.noRepeat,
+    this.centerSlice,
+    this.gaplessPlayback: false
+  }) : image = new FileImage(file, scale: scale),
+       super(key: key);
+
   /// Creates a widget that displays an [ImageStream] obtained from an asset
   /// bundle. The key for the image is given by the `name` argument.
   ///