add image save as jpg and png funcion and testunit

src/TensorFlowNET.Core/APIs/tf.image.cs

@@ -339,6 +339,13 @@ namespace Tensorflow
                 => image_ops_impl.decode_image(contents, channels: channels, dtype: dtype,
                     name: name, expand_animations: expand_animations);
 
+            public Tensor encode_png(Tensor contents, string name = null)
+                    => image_ops_impl.encode_png(contents, name: name);
+
+            public Tensor encode_jpeg(Tensor contents, string name = null)
+                    => image_ops_impl.encode_jpeg(contents, name: name);
+
+
             /// <summary>
             /// Convenience function to check if the 'contents' encodes a JPEG image.
             /// </summary>

src/TensorFlowNET.Core/APIs/tf.io.cs

@@ -16,6 +16,7 @@
 
 using System.Collections.Generic;
 using Tensorflow.IO;
+using Tensorflow.Operations;
 
 namespace Tensorflow
 {
@@ -46,6 +47,12 @@ namespace Tensorflow
             public Tensor[] restore_v2(Tensor prefix, string[] tensor_names,
                 string[] shape_and_slices, TF_DataType[] dtypes, string name = null)
                 => ops.restore_v2(prefix, tensor_names, shape_and_slices, dtypes, name: name);
+
+            public void write_file(string filename, Tensor conentes, string name = null)
+                => write_file(Tensorflow.ops.convert_to_tensor(filename, TF_DataType.TF_STRING), conentes, name);
+
+            public void write_file(Tensor filename, Tensor conentes, string name = null)
+                => gen_ops.write_file(filename, conentes, name);
         }
 
         public GFile gfile = new GFile();

src/TensorFlowNET.Core/Operations/gen_ops.cs

@@ -39083,13 +39083,14 @@ namespace Tensorflow.Operations
         /// <remarks>
         ///    creates directory if not existing.
         /// </remarks>
-        public static Operation write_file(Tensor filename, Tensor contents, string name = "WriteFile")
+        public static Tensor write_file(Tensor filename, Tensor contents, string name = "WriteFile")
         {
             var dict = new Dictionary<string, object>();
             dict["filename"] = filename;
             dict["contents"] = contents;
             var op = tf.OpDefLib._apply_op_helper("WriteFile", name: name, keywords: dict);
-            return op;
+            op.run();
+            return op.output;
         }
 
         /// <summary>

src/TensorFlowNET.Core/Operations/image_ops_impl.cs

@@ -2047,6 +2047,22 @@ new_height, new_width");
             });
         }
 
+        public static Tensor encode_jpeg(Tensor contents, string name = null)
+        {
+            return tf_with(ops.name_scope(name, "encode_jpeg"), scope =>
+            {
+                return gen_ops.encode_jpeg(contents, name:name);
+            });
+        }
+
+        public static Tensor encode_png(Tensor contents, string name = null)
+        {
+            return tf_with(ops.name_scope(name, "encode_png"), scope =>
+            {
+                return gen_ops.encode_png(contents, name: name);
+            });
+        }
+
         public static Tensor is_jpeg(Tensor contents, string name = null)
         {
             return tf_with(ops.name_scope(name, "is_jpeg"), scope =>

test/TensorFlowNET.Graph.UnitTest/ImageTest.cs

@@ -4,6 +4,7 @@ using System.Linq;
 using Tensorflow;
 using static Tensorflow.Binding;
 using System;
+using System.IO;
 
 namespace TensorFlowNET.UnitTest
 {
@@ -164,5 +165,32 @@ namespace TensorFlowNET.UnitTest
             Assert.AreEqual(result.size, 16ul);
             Assert.AreEqual(result[0, 0, 0, 0], 12f);
         }
+
+        [TestMethod]
+        public void ImageSaveTest()
+        {
+            var imgPath = TestHelper.GetFullPathFromDataDir("img001.bmp");
+            var jpegImgPath = TestHelper.GetFullPathFromDataDir("img001.jpeg");
+            var pngImgPath = TestHelper.GetFullPathFromDataDir("img001.png");
+
+            File.Delete(jpegImgPath);
+            File.Delete(pngImgPath);
+
+            var contents = tf.io.read_file(imgPath);
+            var bmp = tf.image.decode_image(contents);
+            Assert.AreEqual(bmp.name, "decode_image/DecodeImage:0");
+
+            var jpeg = tf.image.encode_jpeg(bmp);
+            tf.io.write_file(jpegImgPath, jpeg);
+            Assert.IsTrue(File.Exists(jpegImgPath));
+
+            var png = tf.image.encode_png(bmp);
+            tf.io.write_file(pngImgPath, png);
+            Assert.IsTrue(File.Exists(pngImgPath));
+
+            // 如果要测试图片正确性，可以注释下面两行代码
+            File.Delete(jpegImgPath);
+            File.Delete(pngImgPath);
+        }
     }
 }