file path based apis

README.md

@@ -74,6 +74,16 @@ Many `Image` methods are also fluent.
 
 Here's an example of the code required to resize an image using the default Bicubic resampler then turn the colors into their grayscale equivalent using the BT709 standard matrix.
 
+On platforms supporting netstandard 1.3+
+```csharp
+using (Image image = new Image("foo.jpg"))
+{
+    image.Resize(image.Width / 2, image.Height / 2)
+         .Grayscale()
+         .Save("bar.jpg"); // automatic encoder selected based on extension.
+}
+```
+on netstandard 1.1 - 1.2
 ```csharp
 using (FileStream stream = File.OpenRead("foo.jpg"))
 using (FileStream output = File.OpenWrite("bar.jpg"))

src/ImageSharp/Image.cs

@@ -44,6 +44,23 @@ namespace ImageSharp
         {
         }
 
+#if !NO_FILE_IO
+        /// <summary>
+        /// Initializes a new instance of the <see cref="Image"/> class.
+        /// </summary>
+        /// <param name="filePath">
+        /// A file path to read image information.
+        /// </param>
+        /// <param name="configuration">
+        /// The configuration providing initialization code which allows extending the library.
+        /// </param>
+        /// <exception cref="System.ArgumentNullException">Thrown if the <paramref name="filePath"/> is null.</exception>
+        public Image(string filePath, Configuration configuration = null)
+            : base(filePath, configuration)
+        {
+        }
+#endif
+
         /// <summary>
         /// Initializes a new instance of the <see cref="Image"/> class.
         /// </summary>

src/ImageSharp/Image/Image{TColor}.cs

@@ -63,6 +63,28 @@ namespace ImageSharp
             this.Load(stream);
         }
 
+#if !NO_FILE_IO
+        /// <summary>
+        /// Initializes a new instance of the <see cref="Image{TColor}"/> class.
+        /// </summary>
+        /// <param name="filePath">
+        /// The file containing image information.
+        /// </param>
+        /// <param name="configuration">
+        /// The configuration providing initialization code which allows extending the library.
+        /// </param>
+        /// <exception cref="System.ArgumentNullException">Thrown if the <paramref name="filePath"/> is null.</exception>
+        public Image(string filePath, Configuration configuration = null)
+            : base(configuration)
+        {
+            Guard.NotNull(filePath, nameof(filePath));
+            using (var fs = File.OpenRead(filePath))
+            {
+                this.Load(fs);
+            }
+        }
+#endif
+
         /// <summary>
         /// Initializes a new instance of the <see cref="Image{TColor}"/> class.
         /// </summary>
@@ -189,11 +211,12 @@ namespace ImageSharp
         /// </summary>
         /// <param name="stream">The stream to save the image to.</param>
         /// <param name="format">The format to save the image as.</param>
-        /// <exception cref="System.ArgumentNullException">Thrown if the stream is null.</exception>
+        /// <exception cref="System.ArgumentNullException">Thrown if the stream or format is null.</exception>
         /// <returns>The <see cref="Image{TColor}"/></returns>
         public Image<TColor> Save(Stream stream, IImageFormat format)
         {
             Guard.NotNull(stream, nameof(stream));
+            Guard.NotNull(format, nameof(format));
             format.Encoder.Encode(this, stream);
             return this;
         }
@@ -203,13 +226,14 @@ namespace ImageSharp
         /// </summary>
         /// <param name="stream">The stream to save the image to.</param>
         /// <param name="encoder">The encoder to save the image with.</param>
-        /// <exception cref="System.ArgumentNullException">Thrown if the stream is null.</exception>
+        /// <exception cref="System.ArgumentNullException">Thrown if the stream or encoder is null.</exception>
         /// <returns>
         /// The <see cref="Image{TColor}"/>.
         /// </returns>
         public Image<TColor> Save(Stream stream, IImageEncoder encoder)
         {
             Guard.NotNull(stream, nameof(stream));
+            Guard.NotNull(encoder, nameof(encoder));
             encoder.Encode(this, stream);
 
             // Reset to the start of the stream.
@@ -221,6 +245,58 @@ namespace ImageSharp
             return this;
         }
 
+#if !NO_FILE_IO
+        /// <summary>
+        /// Saves the image to the given stream using the currently loaded image format.
+        /// </summary>
+        /// <param name="filePath">The file path to save the image to.</param>
+        /// <exception cref="System.ArgumentNullException">Thrown if the stream is null.</exception>
+        /// <returns>The <see cref="Image{TColor}"/></returns>
+        public Image<TColor> Save(string filePath)
+        {
+            var ext = Path.GetExtension(filePath).Trim('.');
+            var format = this.Configuration.ImageFormats.SingleOrDefault(f => f.SupportedExtensions.Contains(ext, StringComparer.OrdinalIgnoreCase));
+            if (format == null)
+            {
+                throw new InvalidOperationException($"No image formats have been registered for the file extension '{ext}'.");
+            }
+
+            return this.Save(filePath, format);
+        }
+
+        /// <summary>
+        /// Saves the image to the given stream using the currently loaded image format.
+        /// </summary>
+        /// <param name="filePath">The file path to save the image to.</param>
+        /// <param name="format">The format to save the image as.</param>
+        /// <exception cref="System.ArgumentNullException">Thrown if the format is null.</exception>
+        /// <returns>The <see cref="Image{TColor}"/></returns>
+        public Image<TColor> Save(string filePath, IImageFormat format)
+        {
+            Guard.NotNull(format, nameof(format));
+            using (var fs = File.Create(filePath))
+            {
+                return this.Save(fs, format);
+            }
+        }
+
+        /// <summary>
+        /// Saves the image to the given stream using the currently loaded image format.
+        /// </summary>
+        /// <param name="filePath">The file path to save the image to.</param>
+        /// <param name="encoder">The encoder to save the image with.</param>
+        /// <exception cref="System.ArgumentNullException">Thrown if the encoder is null.</exception>
+        /// <returns>The <see cref="Image{TColor}"/></returns>
+        public Image<TColor> Save(string filePath, IImageEncoder encoder)
+        {
+            Guard.NotNull(encoder, nameof(encoder));
+            using (var fs = File.Create(filePath))
+            {
+                return this.Save(fs, encoder);
+            }
+        }
+#endif
+
         /// <inheritdoc/>
         public override string ToString()
         {

src/ImageSharp/project.json

@@ -46,7 +46,31 @@
     "System.Runtime.CompilerServices.Unsafe": "4.0.0"
   },
   "frameworks": {
+    "netstandard1.3": {
+      "dependencies": {
+        "System.Collections": "4.0.11",
+        "System.Diagnostics.Debug": "4.0.11",
+        "System.Diagnostics.Tools": "4.0.1",
+        "System.IO": "4.1.0",
+        "System.IO.FileSystem": "4.1.0",
+        "System.IO.Compression": "4.1.0",
+        "System.Linq": "4.1.0",
+        "System.Numerics.Vectors": "4.1.1",
+        "System.ObjectModel": "4.0.12",
+        "System.Resources.ResourceManager": "4.0.1",
+        "System.Runtime.Extensions": "4.1.0",
+        "System.Runtime.InteropServices": "4.1.0",
+        "System.Runtime.Numerics": "4.0.1",
+        "System.Text.Encoding.Extensions": "4.0.11",
+        "System.Threading": "4.0.11",
+        "System.Threading.Tasks": "4.0.11",
+        "System.Threading.Tasks.Parallel": "4.0.1"
+      }
+    },
     "netstandard1.1": {
+      "buildOptions": {
+        "define": [ "NO_FILE_IO" ]
+      },
       "dependencies": {
         "System.Collections": "4.0.11",
         "System.Diagnostics.Debug": "4.0.11",

tests/ImageSharp.Tests/Formats/Bmp/BitmapTests.cs

@@ -31,10 +31,7 @@ namespace ImageSharp.Tests
                 string filename = file.GetFileNameWithoutExtension(bitsPerPixel);
                 using (Image image = file.CreateImage())
                 {
-                    using (FileStream output = File.OpenWrite($"{path}/{filename}.bmp"))
-                    {
-                        image.Save(output, new BmpEncoder { BitsPerPixel = bitsPerPixel });
-                    }
+                    image.Save($"{path}/{filename}.bmp", new BmpEncoder { BitsPerPixel = bitsPerPixel });
                 }
             }
         }

tests/ImageSharp.Tests/Image/ImageTests.cs

@@ -29,5 +29,36 @@ namespace ImageSharp.Tests
                 Assert.Equal(450, image.Height);
             }
         }
+
+        [Fact]
+        public void ConstructorFileSystem()
+        {
+            TestFile file = TestFile.Create(TestImages.Bmp.Car);
+            using (Image image = new Image(file.FilePath))
+            {
+                Assert.Equal(600, image.Width);
+                Assert.Equal(450, image.Height);
+            }
+        }
+
+        [Fact]
+        public void ConstructorFileSystem_FileNotFound()
+        {
+            System.IO.FileNotFoundException ex = Assert.Throws<System.IO.FileNotFoundException>(
+                () =>
+                {
+                    new Image(Guid.NewGuid().ToString());
+                });
+        }
+
+        [Fact]
+        public void ConstructorFileSystem_NullPath()
+        {
+            ArgumentNullException ex = Assert.Throws<ArgumentNullException>(
+                () =>
+                {
+                    new Image(null);
+                });
+        }
     }
 }

tests/ImageSharp.Tests/TestFile.cs

@@ -54,6 +54,11 @@ namespace ImageSharp.Tests
         /// </summary>
         public byte[] Bytes { get; }
 
+        /// <summary>
+        /// The file name.
+        /// </summary>
+        public string FilePath => this.file;
+
         /// <summary>
         /// The file name.
         /// </summary>