[Annotation] Take into account the stroke alpha for a FreeText without appearance

src/core/annotation.js

@@ -3511,8 +3511,8 @@ class FreeTextAnnotation extends MarkupAnnotation {
     const { xref } = params;
     this.data.annotationType = AnnotationType.FREETEXT;
     this.setDefaultAppearance(params);
-
     if (!this.appearance && this._isOffscreenCanvasSupported) {
+      const strokeAlpha = params.dict.get("CA");
       const fakeUnicodeFont = new FakeUnicodeFont(xref, "sans-serif");
       const fontData = this.data.defaultAppearanceData;
       this.appearance = fakeUnicodeFont.createAppearance(
@@ -3520,7 +3520,8 @@ class FreeTextAnnotation extends MarkupAnnotation {
         this.rectangle,
         this.rotation,
         fontData.fontSize || 10,
-        fontData.fontColor
+        fontData.fontColor,
+        strokeAlpha
       );
       this._streams.push(this.appearance, FakeUnicodeFont.toUnicodeStream);
     } else if (!this._isOffscreenCanvasSupported) {

src/core/default_appearance.js

@@ -264,7 +264,7 @@ endcmap CMapName currentdict /CMap defineresource pop end end`;
     return this.resources;
   }
 
-  createAppearance(text, rect, rotation, fontSize, bgColor) {
+  createAppearance(text, rect, rotation, fontSize, bgColor, strokeAlpha) {
     const ctx = this._createContext();
     const lines = [];
     let maxWidth = -Infinity;
@@ -321,6 +321,23 @@ endcmap CMapName currentdict /CMap defineresource pop end end`;
       `/${this.fontName.name} ${numberToString(newFontSize)} Tf`,
     ];
 
+    const { resources } = this;
+    strokeAlpha =
+      typeof strokeAlpha === "number" && strokeAlpha >= 0 && strokeAlpha <= 1
+        ? strokeAlpha
+        : 1;
+
+    if (strokeAlpha !== 1) {
+      buffer.push("/R0 gs");
+      const extGState = new Dict(this.xref);
+      const r0 = new Dict(this.xref);
+      r0.set("ca", strokeAlpha);
+      r0.set("CA", strokeAlpha);
+      r0.set("Type", Name.get("ExtGState"));
+      extGState.set("R0", r0);
+      resources.set("ExtGState", extGState);
+    }
+
     const vShift = numberToString(lineHeight);
     for (const line of lines) {
       buffer.push(`0 -${vShift} Td <${stringToUTF16HexString(line)}> Tj`);
@@ -333,7 +350,7 @@ endcmap CMapName currentdict /CMap defineresource pop end end`;
     appearanceStreamDict.set("Type", Name.get("XObject"));
     appearanceStreamDict.set("BBox", [0, 0, w, h]);
     appearanceStreamDict.set("Length", appearance.length);
-    appearanceStreamDict.set("Resources", this.resources);
+    appearanceStreamDict.set("Resources", resources);
 
     if (rotation) {
       const matrix = getRotationMatrix(rotation, w, h);

test/pdfs/.gitignore

@@ -572,3 +572,4 @@
 !bug1811694.pdf
 !bug1811510.pdf
 !bug1815476.pdf
+!issue16021.pdf

test/test_manifest.json

@@ -7349,5 +7349,12 @@
             "value": "bar"
          }
       }
+   },
+   {
+      "id": "issue16021",
+      "file": "pdfs/issue16021.pdf",
+      "md5": "78a12254cac90ba5219a4c5555ea35ed",
+      "rounds": 1,
+      "type": "eq"
    }
 ]