增加 DrawingUtility 类，提供保存图片的扩展方法

Apewer.Windows/Apewer.Windows.csproj

@@ -20,12 +20,14 @@
 	<PropertyGroup Condition="'$(TargetFramework)'=='netcoreapp3.1'">
 		<!-- <UseWPF>true</UseWPF> -->
 		<!-- <UseWindowsForms>true</UseWindowsForms> -->
+		<DefineConstants>DRAWING;$(DefineConstants);$(AdditionalConstants)</DefineConstants>
 	</PropertyGroup>
 	<ItemGroup Condition="'$(TargetFramework)'=='netcoreapp3.1'">
 		<!-- <FrameworkReference Include="Microsoft.AspNetCore.App" /> -->
 		<FrameworkReference Include="Microsoft.WindowsDesktop.App" />
 		<!--<PackageReference Include="System.ServiceProcess.ServiceController" Version="4.4.0" />-->
 		<PackageReference Include="System.ServiceProcess.ServiceController" Version="6.0.0" />
+		<Compile Include="..\Apewer\DrawingUtility.cs" />
 	</ItemGroup>
 
 	<!-- .NET Framework 4.6.1 -->

Apewer/Apewer.csproj

@@ -20,7 +20,7 @@
 
 	<!-- .NET Framework 2.0 -->
 	<PropertyGroup Condition="'$(TargetFramework)'=='net20'">
-        <DefineConstants>NETFX;NET20;$(DefineConstants);$(AdditionalConstants)</DefineConstants>
+		<DefineConstants>NETFX;NET20;DRAWING;$(DefineConstants);$(AdditionalConstants)</DefineConstants>
 	</PropertyGroup>
 	<ItemGroup Condition="'$(TargetFramework)'=='net20'">
 		<Reference Include="System.Web" />
@@ -29,7 +29,7 @@
 
 	<!-- .NET Framework 4.0 -->
 	<PropertyGroup Condition="'$(TargetFramework)'=='net40'">
-        <DefineConstants>NETFX;NET40;HAVE_BIG_INTEGER;$(DefineConstants);$(AdditionalConstants)</DefineConstants>
+		<DefineConstants>NETFX;NET40;DRAWING;HAVE_BIG_INTEGER;$(DefineConstants);$(AdditionalConstants)</DefineConstants>
 	</PropertyGroup>
 	<ItemGroup Condition="'$(TargetFramework)'=='net40'">
 		<Reference Include="System.Web" />
@@ -38,7 +38,7 @@
 
 	<!-- .NET Framework 4.6.1 -->
 	<PropertyGroup Condition="'$(TargetFramework)'=='net461'">
-        <DefineConstants>NETFX;NET461;NET45;HAVE_ASYNC;HAVE_BIG_INTEGER;$(DefineConstants);$(AdditionalConstants)</DefineConstants>
+		<DefineConstants>NETFX;NET461;NET45;DRAWING;HAVE_ASYNC;HAVE_BIG_INTEGER;$(DefineConstants);$(AdditionalConstants)</DefineConstants>
 	</PropertyGroup>
 	<ItemGroup Condition="'$(TargetFramework)'=='net461'">
 		<Reference Include="System.Web" />

Apewer/DrawingUtility.cs

@@ -0,0 +1,123 @@
+#if DRAWING
+
+using System;
+using System.Drawing;
+using System.Drawing.Drawing2D;
+using System.Drawing.Imaging;
+using System.IO;
+
+namespace Apewer
+{
+
+    /// <summary>绘图。</summary>
+    public static class DrawingUtility
+    {
+
+        /// <summary>优化 Graphics 对象的属性，提升绘图质量。</summary>
+        public static Graphics Optimize(this Graphics graphics)
+        {
+            if (graphics != null)
+            {
+                graphics.CompositingMode = CompositingMode.SourceOver;
+                graphics.CompositingQuality = CompositingQuality.HighQuality;
+                graphics.SmoothingMode = SmoothingMode.AntiAlias;
+            }
+            return graphics;
+        }
+
+        /// <summary>保存图像为文件。</summary>
+        /// <exception cref="ArgumentNullException"></exception>
+        public static byte[] Save(this Image image, ImageFormat format)
+        {
+            if (image == null) throw new ArgumentNullException(nameof(image));
+            if (format == null) throw new ArgumentNullException(nameof(format));
+
+            using (var memory = new MemoryStream())
+            {
+                image.Save(memory, format);
+                return memory.ToArray();
+            }
+        }
+
+        /// <summary>保存为 JPEG 文件。</summary>
+        /// <param name="image">Image 实例。</param>
+        /// <param name="quality">JPEG 质量，0 为最低质量，100 为最高质量。</param>
+        /// <exception cref="ArgumentNullException" />
+        /// <exception cref="ArgumentOutOfRangeException" />
+        /// <exception cref="System.Runtime.InteropServices.ExternalException" />
+        public static byte[] SaveAsJpeg(this Image image, int quality = 100)
+        {
+            if (image == null) throw new ArgumentNullException(nameof(image));
+            if (quality < 0 || quality > 100) throw new ArgumentOutOfRangeException(nameof(quality));
+
+            var codec = ImageCodecInfo.GetImageDecoders().Find(x => x.FormatID == ImageFormat.Jpeg.Guid);
+            if (codec == null) throw new System.Runtime.InteropServices.ExternalException($"系统中不存在 JPEG 编码器。");
+
+            var parameters = new EncoderParameters(1);
+            parameters.Param[0] = new EncoderParameter(Encoder.Quality, quality);
+
+            using (var memory = new MemoryStream())
+            {
+                image.Save(memory, codec, parameters);
+                return memory.ToArray();
+            }
+        }
+
+        /// <summary>缩放图像，生成新图像。</summary>
+        /// <param name="image">原始图像。</param>
+        /// <param name="size">新图像的大小。</param>
+        /// <param name="backgroundColor">填充新图像背景色。</param>
+        /// <exception cref="ArgumentNullException"></exception>
+        /// <exception cref="ArgumentOutOfRangeException"></exception>
+        public static Bitmap Scale(this Image image, Size size, Color? backgroundColor = null) => Scale(image, size.Width, size.Height, backgroundColor);
+
+        /// <summary>缩放图像，生成新图像。</summary>
+        /// <param name="image">原始图像。</param>
+        /// <param name="width">新图像的宽度。</param>
+        /// <param name="height">新图像的高度。</param>
+        /// <param name="backgroundColor">填充新图像背景色。</param>
+        /// <exception cref="ArgumentNullException"></exception>
+        /// <exception cref="ArgumentOutOfRangeException"></exception>
+        static Bitmap Scale(this Image image, int width, int height, Color? backgroundColor = null)
+        {
+            if (image == null) throw new ArgumentNullException(nameof(image));
+            if (width < 1) throw new ArgumentOutOfRangeException(nameof(width));
+            if (height < 1) throw new ArgumentOutOfRangeException(nameof(height));
+
+            // 检查原始图像是否为透明格式
+            var rawFormat = image.RawFormat;
+            var isTransparentFormat = rawFormat.Equals(ImageFormat.Png) || rawFormat.Equals(ImageFormat.Gif);
+            var pixelFormat = isTransparentFormat ? PixelFormat.Format32bppArgb : PixelFormat.Format24bppRgb;
+
+            var bitmap = new Bitmap(width, height, pixelFormat);
+            try
+            {
+                using (var graphic = Graphics.FromImage(bitmap))
+                {
+                    graphic.CompositingMode = CompositingMode.SourceOver;
+                    graphic.CompositingQuality = CompositingQuality.HighQuality;
+                    graphic.SmoothingMode = SmoothingMode.AntiAlias;
+
+                    // 填充背景色
+                    if (isTransparentFormat)
+                    {
+                        if (backgroundColor != null && backgroundColor.HasValue) graphic.Clear(backgroundColor.Value);
+                    }
+
+                    // 绘制新图像
+                    graphic.DrawImage(image, 0, 0, width, height);
+                }
+                return bitmap;
+            }
+            catch
+            {
+                bitmap.Dispose();
+                throw;
+            }
+        }
+
+    }
+
+}
+
+#endif