Neuerstellung

- Quelle: https://github.com/oxyplot/oxyplot

Source/OxyPlot.SkiaSharp/JpegExporter.cs

@@ -0,0 +1,95 @@
+// --------------------------------------------------------------------------------------------------------------------
+// <copyright file="JpegExporter.cs" company="OxyPlot">
+//   Copyright (c) 2020 OxyPlot contributors
+// </copyright>
+// --------------------------------------------------------------------------------------------------------------------
+
+namespace OxyPlot.SkiaSharp
+{
+    using global::SkiaSharp;
+    using System.IO;
+
+    /// <summary>
+    /// Provides functionality to export plots to jpeg using the SkiaSharp renderer.
+    /// </summary>
+    public class JpegExporter : IExporter
+    {
+        /// <summary>
+        /// Gets or sets the DPI.
+        /// </summary>
+        public float Dpi { get; set; } = 96;
+
+        /// <summary>
+        /// Gets or sets the export height (in pixels).
+        /// </summary>
+        public int Height { get; set; }
+
+        /// <summary>
+        /// Gets or sets the export width (in pixels).
+        /// </summary>
+        public int Width { get; set; }
+
+        /// <summary>
+        /// Gets or sets the export quality (0-100).
+        /// </summary>
+        public int Quality { get; set; } = 90;
+
+        /// <summary>
+        /// Exports the specified model to a file.
+        /// </summary>
+        /// <param name="model">The model.</param>
+        /// <param name="path">The path.</param>
+        /// <param name="width">The width (points).</param>
+        /// <param name="height">The height (points).</param>
+        /// <param name="quality">The export quality (0-100).</param>
+        /// <param name="dpi">The DPI (dots per inch).</param>
+        public static void Export(IPlotModel model, string path, int width, int height, int quality, float dpi = 96)
+        {
+            using var stream = File.OpenWrite(path);
+            Export(model, stream, width, height, quality, dpi);
+        }
+
+        /// <summary>
+        /// Exports the specified model to a stream.
+        /// </summary>
+        /// <param name="model">The model.</param>
+        /// <param name="stream">The output stream.</param>
+        /// <param name="width">The width (points).</param>
+        /// <param name="height">The height (points).</param>
+        /// <param name="quality">The export quality (0-100).</param>
+        /// <param name="dpi">The DPI (dots per inch).</param>
+        public static void Export(IPlotModel model, Stream stream, int width, int height, int quality, float dpi = 96)
+        {
+            var exporter = new JpegExporter { Width = width, Height = height, Quality = quality, Dpi = dpi };
+            exporter.Export(model, stream);
+        }
+
+        /// <inheritdoc/>
+        public void Export(IPlotModel model, Stream stream)
+        {
+            using var bitmap = new SKBitmap(this.Width, this.Height);
+
+            using (var canvas = new SKCanvas(bitmap))
+            using (var context = new SkiaRenderContext { RenderTarget = RenderTarget.PixelGraphic, SkCanvas = canvas })
+            {
+                canvas.Clear(SKColors.White);
+                var dpiScale = this.Dpi / 96;
+                context.DpiScale = dpiScale;
+                model.Update(true);
+                var backgroundColor = model.Background;
+
+                // jpg doesn't support transparency
+                if (!backgroundColor.IsVisible())
+                {
+                    backgroundColor = OxyColors.White;
+                }
+
+                canvas.Clear(backgroundColor.ToSKColor());
+                model.Render(context, new OxyRect(0, 0, this.Width / dpiScale, this.Height / dpiScale));
+            }
+
+            using var skStream = new SKManagedWStream(stream);
+            bitmap.Encode(skStream, SKEncodedImageFormat.Jpeg, this.Quality);
+        }
+    }
+}