Support PDF highlight annotation with opacity.

core/fpdfdoc/cpvt_generateap.cpp

 // Copyright 2016 PDFium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Original code copyright 2014 Foxit Software Inc. http://www.foxitsoftware.com
 
 #include "core/fpdfdoc/cpvt_generateap.h"
 
 #include "core/fpdfapi/fpdf_font/include/cpdf_font.h"
 #include "core/fpdfapi/fpdf_parser/include/cpdf_dictionary.h"
@@ skipping 520 matching lines @@
                          sAppStream.GetSize(), FALSE, FALSE);
 
   CPDF_Dictionary* pStreamDict = pNormalStream->GetDict();
   pStreamDict->SetAtInteger("FormType", 1);
   pStreamDict->SetAtString("Subtype", "Form");
   pStreamDict->SetAtMatrix("Matrix", CFX_Matrix());
   pStreamDict->SetAtRect("BBox", rect);
 
   CPDF_Dictionary* pGSDict = new CPDF_Dictionary;
   pGSDict->SetAtString("Type", "ExtGState");
-  pGSDict->SetAtNumber("ca", 1);
-  pGSDict->SetAtNumber("CA", 1);
+
+  FX_FLOAT fOpacity =
+      pAnnotDict->KeyExist("CA") ? pAnnotDict->GetNumberBy("CA") : 1;
+  pGSDict->SetAtNumber("ca", fOpacity);
+  pGSDict->SetAtNumber("CA", fOpacity);
   pGSDict->SetAtBoolean("AIS", false);
   pGSDict->SetAtString("BM", "Multiply");
 
   CPDF_Dictionary* pExtGStateDict = new CPDF_Dictionary;
   pExtGStateDict->SetAt("GS", pGSDict);
 
   CPDF_Dictionary* pResourceDict = new CPDF_Dictionary;
   pResourceDict->SetAt("ExtGState", pExtGStateDict);
 
   pStreamDict->SetAt("Resources", pResourceDict);
@@ skipping 258 matching lines @@
                                                  int32_t nFontIndex,
                                                  FX_FLOAT fFontSize) {
   CFX_ByteTextBuf sRet;
   if (pFontMap) {
     CFX_ByteString sFontAlias = pFontMap->GetPDFFontAlias(nFontIndex);
     if (sFontAlias.GetLength() > 0 && fFontSize > 0)
       sRet << "/" << sFontAlias << " " << fFontSize << " Tf\n";
   }
   return sRet.MakeString();
 }