From f0964c7dfde6c0c8c006b55c5ed0cdd2bc131554 Mon Sep 17 00:00:00 2001
From: ritwic <ritwic@gmail.com>
Date: Thu, 19 Jun 2025 07:51:44 +0800
Subject: [PATCH] Apply group blend mode when compositing group to main canvas

---
 src/display/canvas.js | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/src/display/canvas.js b/src/display/canvas.js
index df0556ad0..4c7d5afdf 100644
--- a/src/display/canvas.js
+++ b/src/display/canvas.js
@@ -2464,7 +2464,12 @@ class CanvasGraphics {
         currentMtx,
         dirtyBox
       );
+
+      // Apply the group blend mode and alpha when compositing the group
+      const prevBlendMode = this.pushGroupBlendMode(this.ctx, group.blendMode);
       this.ctx.drawImage(groupCtx.canvas, 0, 0);
+      this.popGroupBlendMode(this.ctx, prevBlendMode);
+
       this.ctx.restore();
       this.compose(dirtyBox);
     }
@@ -3044,6 +3049,22 @@ class CanvasGraphics {
     }
   }
 
+  pushGroupBlendMode(ctx, blendMode) {
+    if (!ctx || !blendMode) {
+      return null;
+    }
+
+    const prev = ctx.globalCompositeOperation;
+    ctx.globalCompositeOperation = blendMode;
+    return prev;
+  }
+
+  popGroupBlendMode(ctx, prev) {
+    if (ctx && prev !== null) {
+      ctx.globalCompositeOperation = prev;
+    }
+  }
+
   isContentVisible() {
     for (let i = this.markedContentStack.length - 1; i >= 0; i--) {
       if (!this.markedContentStack[i].visible) {