增加GIF导出格式

SpineViewer/Exporter/Implementations/ExportArgs/GifExportArgs.cs

@@ -0,0 +1,51 @@
+using System;
+using System.Collections.Generic;
+using System.ComponentModel;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace SpineViewer.Exporter.Implementations.ExportArgs
+{
+    /// <summary>
+    /// GIF 导出参数
+    /// </summary>
+    [ExportImplementation(ExportType.GIF)]
+    public class GifExportArgs : VideoExportArgs
+    {
+        public GifExportArgs(Size resolution, SFML.Graphics.View view, bool renderSelectedOnly) : base(resolution, view, renderSelectedOnly) 
+        {
+            // GIF 的帧率不能太高, 超过 50 帧反而会变慢
+            FPS = 25;
+        }
+
+        /// <summary>
+        /// 调色板最大颜色数量
+        /// </summary>
+        [Category("GIF 参数"), DisplayName("调色板最大颜色数量"), Description("设置调色板使用的最大颜色数量, 越多则色彩保留程度越高")]
+        public uint MaxColors { get => maxColors; set => maxColors = Math.Clamp(value, 2, 256); }
+        private uint maxColors = 256;
+
+        /// <summary>
+        /// 透明度阈值
+        /// </summary>
+        [Category("GIF 参数"), DisplayName("透明度阈值"), Description("小于该值的像素点会被认为是透明像素")]
+        public byte AlphaThreshold { get => alphaThreshold; set => alphaThreshold = value; }
+        private byte alphaThreshold = 128;
+
+        /// <summary>
+        /// 获取构造好的 FFMpegCore 自定义参数
+        /// </summary>
+        [Browsable(false)]
+        public string FFMpegCoreCustomArguments
+        {
+            get
+            {
+                var v = $"[0:v] split [s0][s1]";
+                var s0 = $"[s0] palettegen=reserve_transparent=1:max_colors={MaxColors} [p]";
+                var s1 = $"[s1][p] paletteuse=dither=bayer:alpha_threshold={AlphaThreshold}";
+                return $"-filter_complex \"{v};{s0};{s1}\"";
+            }
+        }
+    }
+}

SpineViewer/Exporter/Implementations/Exporter/GifExporter.cs

@@ -0,0 +1,76 @@
+using FFMpegCore.Pipes;
+using FFMpegCore;
+using SpineViewer.Exporter.Implementations.ExportArgs;
+using System;
+using System.Collections.Generic;
+using System.ComponentModel;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using FFMpegCore.Arguments;
+
+namespace SpineViewer.Exporter.Implementations.Exporter
+{
+    /// <summary>
+    /// GIF 动图导出器
+    /// </summary>
+    [ExportImplementation(ExportType.GIF)]
+    public class GifExporter : VideoExporter
+    {
+        public GifExporter(GifExportArgs exportArgs) : base(exportArgs) { }
+
+        protected override void ExportSingle(Spine.Spine[] spinesToRender, BackgroundWorker? worker = null)
+        {
+            var args = (GifExportArgs)ExportArgs;
+
+            // 导出单个时必定提供输出文件夹
+            var filename = $"{timestamp}_{args.FPS:f0}_{args.MaxColors}_{args.AlphaThreshold}.gif";
+            var savePath = Path.Combine(args.OutputDir, filename);
+
+            var videoFramesSource = new RawVideoPipeSource(GetFrames(spinesToRender, worker)) { FrameRate = args.FPS };
+            try
+            {
+                FFMpegArguments
+                .FromPipeInput(videoFramesSource)
+                .OutputToFile(savePath, true, options => options
+                .ForceFormat("gif")
+                .WithCustomArgument(args.FFMpegCoreCustomArguments))
+                .ProcessSynchronously();
+            }
+            catch (Exception ex)
+            {
+                Program.Logger.Error(ex.ToString());
+                Program.Logger.Error("Failed to export gif {}", savePath);
+            }
+        }
+
+        protected override void ExportIndividual(Spine.Spine[] spinesToRender, BackgroundWorker? worker = null)
+        {
+            var args = (GifExportArgs)ExportArgs;
+            foreach (var spine in spinesToRender)
+            {
+                if (worker?.CancellationPending == true) break; // 取消的日志在 GetFrames 里输出
+
+                // 如果提供了输出文件夹, 则全部导出到输出文件夹, 否则导出到各自的文件夹下
+                var filename = $"{spine.Name}_{timestamp}_{args.FPS:f0}_{args.MaxColors}_{args.AlphaThreshold}.gif";
+                var savePath = Path.Combine(args.OutputDir ?? spine.AssetsDir, filename);
+
+                var videoFramesSource = new RawVideoPipeSource(GetFrames(spine, worker)) { FrameRate = args.FPS };
+                try
+                {
+                    FFMpegArguments
+                    .FromPipeInput(videoFramesSource)
+                    .OutputToFile(savePath, true, options => options
+                    .ForceFormat("gif")
+                    .WithCustomArgument(args.FFMpegCoreCustomArguments))
+                    .ProcessSynchronously();
+                }
+                catch (Exception ex)
+                {
+                    Program.Logger.Error(ex.ToString());
+                    Program.Logger.Error("Failed to export gif {} {}", savePath, spine.SkelPath);
+                }
+            }
+        }
+    }
+}