diff --git a/SpineViewer/Spine/BlendModeSFML.cs b/SpineViewer/Spine/BlendModeSFML.cs
index a8142bb..f89d1bd 100644
--- a/SpineViewer/Spine/BlendModeSFML.cs
+++ b/SpineViewer/Spine/BlendModeSFML.cs
@@ -7,36 +7,86 @@ using System.Threading.Tasks;
 namespace SpineViewer.Spine
 {
     /// <summary>
-    /// SFML 混合模式
+    /// SFML 混合模式, 预乘模式下输入和输出的像素值都是预乘的
     /// </summary>
     public static class BlendModeSFML
     {
-        /// <summary>
-        /// Alpha Blend
-        /// <code>
-        /// res.c = src.c * src.a + dst.c * (1 - src.a)
-        /// res.a = src.a * 1     + dst.a * (1 - src.a)
-        /// </code>
-        /// </summary>
-        public static SFML.Graphics.BlendMode Normal = SFML.Graphics.BlendMode.Alpha;
+        ///// <summary>
+        ///// Normal Blend, 无预乘, 仅在 dst.a 是 1 时得到正确结果, 其余情况是有偏结果
+        ///// <para>当 <c>src.c &lt; dst.c</c> 时, 结果偏大, 例如 src 是半透明纯黑, dst 是全透明纯白</para>
+        ///// <para>当 <c>src.c &gt; dst.c</c> 时, 结果偏小, 例如 src 是半透明纯白, dst 是全透明纯黑</para>
+        ///// <code>
+        ///// res.c = src.c * src.a + dst.c * (1 - src.a)
+        ///// res.a = src.a *     1 + dst.a * (1 - src.a)
+        ///// </code>
+        ///// </summary>
+        //public static SFML.Graphics.BlendMode Normal = new(
+        //    SFML.Graphics.BlendMode.Factor.SrcAlpha,
+        //    SFML.Graphics.BlendMode.Factor.OneMinusSrcAlpha,
+        //    SFML.Graphics.BlendMode.Equation.Add,
+        //    SFML.Graphics.BlendMode.Factor.One,
+        //    SFML.Graphics.BlendMode.Factor.OneMinusSrcAlpha,
+        //    SFML.Graphics.BlendMode.Equation.Add
+        //);
+
+        ///// <summary>
+        ///// Additive Blend, 无预乘, 仅在 dst.a 是 1 时得到正确结果, 其余情况是有偏结果
+        ///// <para>当 <c>src.a + dst.a >= 1</c> 时, 结果偏大, 例如 src 是不透明纯黑, dst 是全透明纯白</para>
+        ///// <para>当 <c>src.a + dst.a &lt; 1</c> 时, 结果偏差方式类似 <see cref="Normal"/>, 均可假设 dst 是全透明纯白进行判断</para>
+        ///// <code>
+        ///// res.c = src.c * src.a + dst.c * 1
+        ///// res.a = src.a *     1 + dst.a * 1
+        ///// </code>
+        ///// </summary>
+        //public static SFML.Graphics.BlendMode Additive = new(
+        //    SFML.Graphics.BlendMode.Factor.SrcAlpha,
+        //    SFML.Graphics.BlendMode.Factor.One,
+        //    SFML.Graphics.BlendMode.Equation.Add,
+        //    SFML.Graphics.BlendMode.Factor.One,
+        //    SFML.Graphics.BlendMode.Factor.One,
+        //    SFML.Graphics.BlendMode.Equation.Add
+        //);
 
         /// <summary>
-        /// Additive Blend
+        /// Normal Blend with PremultipliedAlpha
         /// <code>
-        /// res.c = src.c * src.a + dst.c * 1
-        /// res.a = src.a * 1     + dst.a * 1
+        /// [res.c * res.a] = [src.c * src.a] * 1 + [dst.c * dst.a] * (1 - src.a)
+        ///          res.a  =          src.a  * 1 +          dst.a  * (1 - src.a)
         /// </code>
         /// </summary>
-        public static SFML.Graphics.BlendMode Additive = SFML.Graphics.BlendMode.Add;
+        public static SFML.Graphics.BlendMode NormalPma = new(
+            SFML.Graphics.BlendMode.Factor.One,
+            SFML.Graphics.BlendMode.Factor.OneMinusSrcAlpha,
+            SFML.Graphics.BlendMode.Equation.Add,
+            SFML.Graphics.BlendMode.Factor.One,
+            SFML.Graphics.BlendMode.Factor.OneMinusSrcAlpha,
+            SFML.Graphics.BlendMode.Equation.Add
+        );
 
         /// <summary>
-        /// Multiply Blend (PremultipliedAlpha Only)
+        /// Additive Blend with PremultipliedAlpha
+        /// <code>
+        /// [res.c * res.a] = [src.c * src.a] * 1 + [dst.c * dst.a] * 1
+        ///          res.a  =          src.a  * 1 +          dst.a  * 1
+        /// </code>
+        /// </summary>
+        public static SFML.Graphics.BlendMode AdditivePma = new(
+            SFML.Graphics.BlendMode.Factor.One,
+            SFML.Graphics.BlendMode.Factor.One,
+            SFML.Graphics.BlendMode.Equation.Add,
+            SFML.Graphics.BlendMode.Factor.One,
+            SFML.Graphics.BlendMode.Factor.One,
+            SFML.Graphics.BlendMode.Equation.Add
+        );
+
+        /// <summary>
+        /// Multiply Blend with PremultipliedAlpha
         /// <code>
         /// res.c = src.c * dst.c + dst.c * (1 - src.a)
-        /// res.a = src.a * 1     + dst.a * (1 - src.a)
+        /// res.a = src.a *     1 + dst.a * (1 - src.a)
         /// </code>
         /// </summary>
-        public static SFML.Graphics.BlendMode Multiply = new(
+        public static SFML.Graphics.BlendMode MultiplyPma = new(
             SFML.Graphics.BlendMode.Factor.DstColor,
             SFML.Graphics.BlendMode.Factor.OneMinusSrcAlpha,
             SFML.Graphics.BlendMode.Equation.Add,
@@ -46,13 +96,13 @@ namespace SpineViewer.Spine
         );
 
         /// <summary>
-        /// Screen Blend (PremultipliedAlpha Only)
+        /// Screen Blend with PremultipliedAlpha Only
         /// <code>
         /// res.c = src.c * 1 + dst.c * (1 - src.c) = 1 - [(1 - src.c)(1 - dst.c)]
         /// res.a = src.a * 1 + dst.a * (1 - src.a)
         /// </code>
         /// </summary>
-        public static SFML.Graphics.BlendMode Screen = new(
+        public static SFML.Graphics.BlendMode ScreenPma = new(
             SFML.Graphics.BlendMode.Factor.One,
             SFML.Graphics.BlendMode.Factor.OneMinusSrcColor,
             SFML.Graphics.BlendMode.Equation.Add,
diff --git a/SpineViewer/Spine/Implementations/Spine/Spine21.cs b/SpineViewer/Spine/Implementations/Spine/Spine21.cs
index 34ca268..f91c6d4 100644
--- a/SpineViewer/Spine/Implementations/Spine/Spine21.cs
+++ b/SpineViewer/Spine/Implementations/Spine/Spine21.cs
@@ -261,6 +261,7 @@ namespace SpineViewer.Spine.Implementations.Spine
         {
             vertexArray.Clear();
             states.Texture = null;
+            states.Shader = Shader.GetShader(usePremultipliedAlpha);
 
             // 要用 DrawOrder 而不是 Slots
             foreach (var slot in skeleton.DrawOrder)
@@ -322,18 +323,13 @@ namespace SpineViewer.Spine.Implementations.Spine
                 }
 
                 // 似乎 2.1.x 也没有 BlendMode
-                SFML.Graphics.BlendMode blendMode = slot.Data.AdditiveBlending ? BlendModeSFML.Additive : BlendModeSFML.Normal;
+                SFML.Graphics.BlendMode blendMode = slot.Data.AdditiveBlending ? BlendModeSFML.AdditivePma : BlendModeSFML.NormalPma;
 
                 states.Texture ??= texture;
                 if (states.BlendMode != blendMode || states.Texture != texture)
                 {
                     if (vertexArray.VertexCount > 0)
                     {
-                        if (usePremultipliedAlpha && (states.BlendMode == BlendModeSFML.Normal || states.BlendMode == BlendModeSFML.Additive))
-                            states.Shader = Shader.FragmentShader;
-                        else
-                            states.Shader = null;
-
                         // 调试纹理
                         if (!isDebug || debugTexture)
                             target.Draw(vertexArray, states);
@@ -377,11 +373,6 @@ namespace SpineViewer.Spine.Implementations.Spine
 
                 //clipping.ClipEnd(slot);
             }
-
-            if (usePremultipliedAlpha && (states.BlendMode == BlendModeSFML.Normal || states.BlendMode == BlendModeSFML.Additive))
-                states.Shader = Shader.FragmentShader;
-            else
-                states.Shader = null;
             //clipping.ClipEnd();
 
             // 调试纹理
diff --git a/SpineViewer/Spine/Implementations/Spine/Spine36.cs b/SpineViewer/Spine/Implementations/Spine/Spine36.cs
index b67213c..ddc365a 100644
--- a/SpineViewer/Spine/Implementations/Spine/Spine36.cs
+++ b/SpineViewer/Spine/Implementations/Spine/Spine36.cs
@@ -208,10 +208,10 @@ namespace SpineViewer.Spine.Implementations.Spine
         {
             return spineBlendMode switch
             {
-                BlendMode.Normal => BlendModeSFML.Normal,
-                BlendMode.Additive => BlendModeSFML.Additive,
-                BlendMode.Multiply => BlendModeSFML.Multiply,
-                BlendMode.Screen => BlendModeSFML.Screen,
+                BlendMode.Normal => BlendModeSFML.NormalPma,
+                BlendMode.Additive => BlendModeSFML.AdditivePma,
+                BlendMode.Multiply => BlendModeSFML.MultiplyPma,
+                BlendMode.Screen => BlendModeSFML.ScreenPma,
                 _ => throw new NotImplementedException($"{spineBlendMode}"),
             };
         }
@@ -220,6 +220,7 @@ namespace SpineViewer.Spine.Implementations.Spine
         {
             vertexArray.Clear();
             states.Texture = null;
+            states.Shader = Shader.GetShader(usePremultipliedAlpha);
 
             // 要用 DrawOrder 而不是 Slots
             foreach (var slot in skeleton.DrawOrder)
@@ -286,11 +287,6 @@ namespace SpineViewer.Spine.Implementations.Spine
                 {
                     if (vertexArray.VertexCount > 0)
                     {
-                        if (usePremultipliedAlpha && (states.BlendMode == BlendModeSFML.Normal || states.BlendMode == BlendModeSFML.Additive))
-                            states.Shader = Shader.FragmentShader;
-                        else
-                            states.Shader = null;
-
                         // 调试纹理
                         if (!isDebug || debugTexture)
                             target.Draw(vertexArray, states);
@@ -336,11 +332,6 @@ namespace SpineViewer.Spine.Implementations.Spine
             }
             clipping.ClipEnd();
 
-            if (usePremultipliedAlpha && (states.BlendMode == BlendModeSFML.Normal || states.BlendMode == BlendModeSFML.Additive))
-                states.Shader = Shader.FragmentShader;
-            else
-                states.Shader = null;
-
             // 调试纹理
             if (!isDebug || debugTexture)
                 target.Draw(vertexArray, states);
diff --git a/SpineViewer/Spine/Implementations/Spine/Spine37.cs b/SpineViewer/Spine/Implementations/Spine/Spine37.cs
index 89a0a00..61d66ce 100644
--- a/SpineViewer/Spine/Implementations/Spine/Spine37.cs
+++ b/SpineViewer/Spine/Implementations/Spine/Spine37.cs
@@ -178,10 +178,10 @@ namespace SpineViewer.Spine.Implementations.Spine
         {
             return spineBlendMode switch
             {
-                BlendMode.Normal => BlendModeSFML.Normal,
-                BlendMode.Additive => BlendModeSFML.Additive,
-                BlendMode.Multiply => BlendModeSFML.Multiply,
-                BlendMode.Screen => BlendModeSFML.Screen,
+                BlendMode.Normal => BlendModeSFML.NormalPma,
+                BlendMode.Additive => BlendModeSFML.AdditivePma,
+                BlendMode.Multiply => BlendModeSFML.MultiplyPma,
+                BlendMode.Screen => BlendModeSFML.ScreenPma,
                 _ => throw new NotImplementedException($"{spineBlendMode}"),
             };
         }
@@ -190,6 +190,7 @@ namespace SpineViewer.Spine.Implementations.Spine
         {
             vertexArray.Clear();
             states.Texture = null;
+            states.Shader = Shader.GetShader(usePremultipliedAlpha);
 
             // 要用 DrawOrder 而不是 Slots
             foreach (var slot in skeleton.DrawOrder)
@@ -256,12 +257,6 @@ namespace SpineViewer.Spine.Implementations.Spine
                 {
                     if (vertexArray.VertexCount > 0)
                     {
-                        // XXX: 实测不用设置 sampler2D 的值也正确
-                        if (usePremultipliedAlpha && (states.BlendMode == BlendModeSFML.Normal || states.BlendMode == BlendModeSFML.Additive))
-                            states.Shader = Shader.FragmentShader;
-                        else
-                            states.Shader = null;
-
                         // 调试纹理
                         if (!isDebug || debugTexture)
                             target.Draw(vertexArray, states);
@@ -307,11 +302,6 @@ namespace SpineViewer.Spine.Implementations.Spine
             }
             clipping.ClipEnd();
 
-            if (usePremultipliedAlpha && (states.BlendMode == BlendModeSFML.Normal || states.BlendMode == BlendModeSFML.Additive))
-                states.Shader = Shader.FragmentShader;
-            else
-                states.Shader = null;
-
             // 调试纹理
             if (!isDebug || debugTexture)
                 target.Draw(vertexArray, states);
diff --git a/SpineViewer/Spine/Implementations/Spine/Spine38.cs b/SpineViewer/Spine/Implementations/Spine/Spine38.cs
index 76953ff..b8f2073 100644
--- a/SpineViewer/Spine/Implementations/Spine/Spine38.cs
+++ b/SpineViewer/Spine/Implementations/Spine/Spine38.cs
@@ -184,10 +184,10 @@ namespace SpineViewer.Spine.Implementations.Spine
         {
             return spineBlendMode switch
             {
-                BlendMode.Normal => BlendModeSFML.Normal,
-                BlendMode.Additive => BlendModeSFML.Additive,
-                BlendMode.Multiply => BlendModeSFML.Multiply,
-                BlendMode.Screen => BlendModeSFML.Screen,
+                BlendMode.Normal => BlendModeSFML.NormalPma,
+                BlendMode.Additive => BlendModeSFML.AdditivePma,
+                BlendMode.Multiply => BlendModeSFML.MultiplyPma,
+                BlendMode.Screen => BlendModeSFML.ScreenPma,
                 _ => throw new NotImplementedException($"{spineBlendMode}"),
             };
         }
@@ -196,6 +196,7 @@ namespace SpineViewer.Spine.Implementations.Spine
         {
             vertexArray.Clear();
             states.Texture = null;
+            states.Shader = Shader.GetShader(usePremultipliedAlpha);
 
             // 要用 DrawOrder 而不是 Slots
             foreach (var slot in skeleton.DrawOrder)
@@ -262,14 +263,8 @@ namespace SpineViewer.Spine.Implementations.Spine
                 {
                     if (vertexArray.VertexCount > 0)
                     {
-                        // XXX: 实测不用设置 sampler2D 的值也正确
-                        if (usePremultipliedAlpha && (states.BlendMode == BlendModeSFML.Normal || states.BlendMode == BlendModeSFML.Additive))
-                            states.Shader = Shader.FragmentShader;
-                        else
-                            states.Shader = null;
-
                         // 调试纹理
-                        if (!isDebug || debugTexture)
+                        if (!isDebug || debugTexture) 
                             target.Draw(vertexArray, states);
 
                         vertexArray.Clear();
@@ -313,11 +308,6 @@ namespace SpineViewer.Spine.Implementations.Spine
             }
             clipping.ClipEnd();
 
-            if (usePremultipliedAlpha && (states.BlendMode == BlendModeSFML.Normal || states.BlendMode == BlendModeSFML.Additive))
-                states.Shader = Shader.FragmentShader;
-            else
-                states.Shader = null;
-
             // 调试纹理
             if (!isDebug || debugTexture)
                 target.Draw(vertexArray, states);
diff --git a/SpineViewer/Spine/Implementations/Spine/Spine40.cs b/SpineViewer/Spine/Implementations/Spine/Spine40.cs
index 528e58a..b6ec861 100644
--- a/SpineViewer/Spine/Implementations/Spine/Spine40.cs
+++ b/SpineViewer/Spine/Implementations/Spine/Spine40.cs
@@ -180,10 +180,10 @@ namespace SpineViewer.Spine.Implementations.Spine
         {
             return spineBlendMode switch
             {
-                BlendMode.Normal => BlendModeSFML.Normal,
-                BlendMode.Additive => BlendModeSFML.Additive,
-                BlendMode.Multiply => BlendModeSFML.Multiply,
-                BlendMode.Screen => BlendModeSFML.Screen,
+                BlendMode.Normal => BlendModeSFML.NormalPma,
+                BlendMode.Additive => BlendModeSFML.AdditivePma,
+                BlendMode.Multiply => BlendModeSFML.MultiplyPma,
+                BlendMode.Screen => BlendModeSFML.ScreenPma,
                 _ => throw new NotImplementedException($"{spineBlendMode}"),
             };
         }
@@ -192,6 +192,7 @@ namespace SpineViewer.Spine.Implementations.Spine
         {
             vertexArray.Clear();
             states.Texture = null;
+            states.Shader = Shader.GetShader(usePremultipliedAlpha);
 
             // 要用 DrawOrder 而不是 Slots
             foreach (var slot in skeleton.DrawOrder)
@@ -258,12 +259,6 @@ namespace SpineViewer.Spine.Implementations.Spine
                 {
                     if (vertexArray.VertexCount > 0)
                     {
-                        // XXX: 实测不用设置 sampler2D 的值也正确
-                        if (usePremultipliedAlpha && (states.BlendMode == BlendModeSFML.Normal || states.BlendMode == BlendModeSFML.Additive))
-                            states.Shader = Shader.FragmentShader;
-                        else
-                            states.Shader = null;
-
                         // 调试纹理
                         if (!isDebug || debugTexture)
                             target.Draw(vertexArray, states);
@@ -309,11 +304,6 @@ namespace SpineViewer.Spine.Implementations.Spine
             }
             clipping.ClipEnd();
 
-            if (usePremultipliedAlpha && (states.BlendMode == BlendModeSFML.Normal || states.BlendMode == BlendModeSFML.Additive))
-                states.Shader = Shader.FragmentShader;
-            else
-                states.Shader = null;
-
             // 调试纹理
             if (!isDebug || debugTexture)
                 target.Draw(vertexArray, states);
diff --git a/SpineViewer/Spine/Implementations/Spine/Spine41.cs b/SpineViewer/Spine/Implementations/Spine/Spine41.cs
index f995319..3471db1 100644
--- a/SpineViewer/Spine/Implementations/Spine/Spine41.cs
+++ b/SpineViewer/Spine/Implementations/Spine/Spine41.cs
@@ -180,10 +180,10 @@ namespace SpineViewer.Spine.Implementations.Spine
         {
             return spineBlendMode switch
             {
-                BlendMode.Normal => BlendModeSFML.Normal,
-                BlendMode.Additive => BlendModeSFML.Additive,
-                BlendMode.Multiply => BlendModeSFML.Multiply,
-                BlendMode.Screen => BlendModeSFML.Screen,
+                BlendMode.Normal => BlendModeSFML.NormalPma,
+                BlendMode.Additive => BlendModeSFML.AdditivePma,
+                BlendMode.Multiply => BlendModeSFML.MultiplyPma,
+                BlendMode.Screen => BlendModeSFML.ScreenPma,
                 _ => throw new NotImplementedException($"{spineBlendMode}"),
             };
         }
@@ -192,6 +192,7 @@ namespace SpineViewer.Spine.Implementations.Spine
         {
             vertexArray.Clear();
             states.Texture = null;
+            states.Shader = Shader.GetShader(usePremultipliedAlpha);
 
             // 要用 DrawOrder 而不是 Slots
             foreach (var slot in skeleton.DrawOrder)
@@ -258,12 +259,6 @@ namespace SpineViewer.Spine.Implementations.Spine
                 {
                     if (vertexArray.VertexCount > 0)
                     {
-                        // XXX: 实测不用设置 sampler2D 的值也正确
-                        if (usePremultipliedAlpha && (states.BlendMode == BlendModeSFML.Normal || states.BlendMode == BlendModeSFML.Additive))
-                            states.Shader = Shader.FragmentShader;
-                        else
-                            states.Shader = null;
-
                         // 调试纹理
                         if (!isDebug || debugTexture)
                             target.Draw(vertexArray, states);
@@ -309,11 +304,6 @@ namespace SpineViewer.Spine.Implementations.Spine
             }
             clipping.ClipEnd();
 
-            if (usePremultipliedAlpha && (states.BlendMode == BlendModeSFML.Normal || states.BlendMode == BlendModeSFML.Additive))
-                states.Shader = Shader.FragmentShader;
-            else
-                states.Shader = null;
-
             // 调试纹理
             if (!isDebug || debugTexture)
                 target.Draw(vertexArray, states);
diff --git a/SpineViewer/Spine/Implementations/Spine/Spine42.cs b/SpineViewer/Spine/Implementations/Spine/Spine42.cs
index d6fc73e..1697385 100644
--- a/SpineViewer/Spine/Implementations/Spine/Spine42.cs
+++ b/SpineViewer/Spine/Implementations/Spine/Spine42.cs
@@ -180,10 +180,10 @@ namespace SpineViewer.Spine.Implementations.Spine
         {
             return spineBlendMode switch
             {
-                BlendMode.Normal => BlendModeSFML.Normal,
-                BlendMode.Additive => BlendModeSFML.Additive,
-                BlendMode.Multiply => BlendModeSFML.Multiply,
-                BlendMode.Screen => BlendModeSFML.Screen,
+                BlendMode.Normal => BlendModeSFML.NormalPma,
+                BlendMode.Additive => BlendModeSFML.AdditivePma,
+                BlendMode.Multiply => BlendModeSFML.MultiplyPma,
+                BlendMode.Screen => BlendModeSFML.ScreenPma,
                 _ => throw new NotImplementedException($"{spineBlendMode}"),
             };
         }
@@ -192,6 +192,7 @@ namespace SpineViewer.Spine.Implementations.Spine
         {
             vertexArray.Clear();
             states.Texture = null;
+            states.Shader = Shader.GetShader(usePremultipliedAlpha);
 
             // 要用 DrawOrder 而不是 Slots
             foreach (var slot in skeleton.DrawOrder)
@@ -258,12 +259,6 @@ namespace SpineViewer.Spine.Implementations.Spine
                 {
                     if (vertexArray.VertexCount > 0)
                     {
-                        // XXX: 实测不用设置 sampler2D 的值也正确
-                        if (usePremultipliedAlpha && (states.BlendMode == BlendModeSFML.Normal || states.BlendMode == BlendModeSFML.Additive))
-                            states.Shader = Shader.FragmentShader;
-                        else
-                            states.Shader = null;
-
                         // 调试纹理
                         if (!isDebug || debugTexture)
                             target.Draw(vertexArray, states);
@@ -309,11 +304,6 @@ namespace SpineViewer.Spine.Implementations.Spine
             }
             clipping.ClipEnd();
 
-            if (usePremultipliedAlpha && (states.BlendMode == BlendModeSFML.Normal || states.BlendMode == BlendModeSFML.Additive))
-                states.Shader = Shader.FragmentShader;
-            else
-                states.Shader = null;
-
             // 调试纹理
             if (!isDebug || debugTexture)
                 target.Draw(vertexArray, states);
diff --git a/SpineViewer/Spine/Shader.cs b/SpineViewer/Spine/Shader.cs
index fd3f206..a2b2ded 100644
--- a/SpineViewer/Spine/Shader.cs
+++ b/SpineViewer/Spine/Shader.cs
@@ -9,19 +9,44 @@ namespace SpineViewer.Spine
     public static class Shader
     {
         /// <summary>
-        /// 用于解决 PMA 和渐变动画问题的片段着色器
+        /// 用于非预乘纹理的 fragment shader, 乘上了插值后的透明度用于实现透明度变化(插值预乘), 并且输出预乘后的像素值
         /// </summary>
-        private const string FRAGMENT_SHADER = (
+        private const string FRAGMENT_VertexAlpha = (
             "uniform sampler2D t;" +
-            "void main() { vec4 p = texture2D(t, gl_TexCoord[0].xy);" +
-            "if (p.a > 0) p.rgb /= max(max(max(p.r, p.g), p.b), p.a);" +
+            "void main() { vec4 p = texture(t, gl_TexCoord[0].xy);" +
+            "p.rgb *= p.a * gl_Color.a;" +
             "gl_FragColor = gl_Color * p; }"
         );
 
         /// <summary>
-        /// 针对预乘 Alpha 通道的片段着色器
+        /// 用于预乘纹理的 fragment shader, 乘上了插值后的透明度用于实现透明度变化(插值预乘)
         /// </summary>
-        public static SFML.Graphics.Shader? FragmentShader { get; private set; }
+        private const string FRAGMENT_VertexAlphaPma = (
+            "uniform sampler2D t;" +
+            "void main() { vec4 p = texture(t, gl_TexCoord[0].xy);" +
+            "p.rgb *= gl_Color.a;" +
+            "gl_FragColor = gl_Color * p; }"
+        );
+
+        /// <summary>
+        /// 预乘转非预乘 fragment shader
+        /// </summary>
+        private const string FRAGMENT_PmaInv = (
+            "uniform sampler2D t;" +
+            "void main() { vec4 p = texture(t, gl_TexCoord[0].xy);" +
+            "p.rgb *= gl_Color.a;" +
+            "gl_FragColor = gl_Color * p; }"
+        );
+
+        /// <summary>
+        /// 考虑了顶点透明度变化的着色器, 输入是非预乘纹理像素, 输出是预乘像素
+        /// </summary>
+        private static SFML.Graphics.Shader? VertexAlpha = null;
+
+        /// <summary>
+        /// 考虑了顶点透明度变化的着色器, 输入和输出均是预乘像素值
+        /// </summary>
+        private static SFML.Graphics.Shader? VertexAlphaPma = null;
 
         /// <summary>
         /// 加载 Shader, 可能会存在异常导致着色器加载失败
@@ -29,7 +54,21 @@ namespace SpineViewer.Spine
         /// <exception cref="SFML.LoadingFailedException"></exception>
         public static void Init()
         {
-            FragmentShader = SFML.Graphics.Shader.FromString(null, null, FRAGMENT_SHADER);
+            VertexAlpha = SFML.Graphics.Shader.FromString(null, null, FRAGMENT_VertexAlpha);
+            VertexAlphaPma = SFML.Graphics.Shader.FromString(null, null, FRAGMENT_VertexAlphaPma);
+        }
+
+        /// <summary>
+        /// 获取合适的着色器
+        /// </summary>
+        /// <param name="pma">纹理是否是预乘的</param>
+        /// <param name="twoColor">是否是双色着色的(TODO)</param>
+        public static SFML.Graphics.Shader? GetShader(bool pma, bool twoColor = false)
+        {
+            if (pma)
+                return VertexAlphaPma;
+            else
+                return VertexAlpha;
         }
     }
 }