Reset alpha before drawing a colored glyph in type 3 font

It fixes #21430.

src/display/canvas.js

@@ -2965,6 +2965,14 @@ class CanvasGraphics {
         warn(`Type3 character "${glyph.operatorListId}" is not available.`);
       } else if (this.contentVisible) {
         this.save();
+        // A d0 (setCharWidth) glyph is colored (see Table 113 in pdf 1.7 specs)
+        // unlike a d1 glyph painted as a stencil mask with the current fill
+        // color. The constant alphas (ca/CA) are the opacity of that current
+        // color, so they must not attenuate a d0 glyph.
+        if (operatorList.fnArray[0] === OPS.setCharWidth) {
+          current.fillAlpha = current.strokeAlpha = 1;
+          ctx.globalAlpha = 1;
+        }
         ctx.scale(fontSize, fontSize);
         ctx.transform(...fontMatrix);
         this.executeOperatorList(operatorList);

test/pdfs/issue21430.pdf.link

@@ -0,0 +1 @@
+https://github.com/user-attachments/files/28821514/xxx.pdf

test/test_manifest.json

@@ -14429,5 +14429,15 @@
     "type": "eq",
     "annotations": true,
     "forms": true
+  },
+  {
+    "id": "issue21430",
+    "file": "pdfs/issue21430.pdf",
+    "md5": "e317f63bdfd6f3d1939a52c983379454",
+    "rounds": 1,
+    "link": true,
+    "firstPage": 1,
+    "lastPage": 1,
+    "type": "eq"
   }
 ]