Generate default AP stream for underline annotation.

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 425 matching lines @@
           pStreamResFontList->SetAtReference(sFontName, pDoc, pFontDict);
       } else {
         pStreamDict->SetAt("Resources", pFormDict->GetDictBy("DR")->Clone());
         pStreamResList = pStreamDict->GetDictBy("Resources");
       }
     }
   }
   return true;
 }
 
+CPDF_Dictionary* GenerateExtGStateDict(CFX_ByteString sName,
+                                       FX_FLOAT fCAForStroke,
+                                       FX_FLOAT fCAForNonStroke,
+                                       CFX_ByteString sBlendMode) {
+  CPDF_Dictionary* pGSDict = new CPDF_Dictionary;
+  pGSDict->SetAtString("Type", "ExtGState");
+  pGSDict->SetAtNumber("CA", fCAForStroke);
+  pGSDict->SetAtNumber("ca", fCAForNonStroke);
+  pGSDict->SetAtBoolean("AIS", false);
+  pGSDict->SetAtString("BM", sBlendMode);
+
+  CPDF_Dictionary* pExtGStateDict = new CPDF_Dictionary;
+  pExtGStateDict->SetAt(sName, pGSDict);
+
+  return pExtGStateDict;
+}
+
 }  // namespace
 
 bool FPDF_GenerateAP(CPDF_Document* pDoc, CPDF_Dictionary* pAnnotDict) {
   if (!pAnnotDict || pAnnotDict->GetStringBy("Subtype") != "Widget")
     return false;
 
   CFX_ByteString field_type = FPDF_GetFieldAttr(pAnnotDict, "FT")->GetString();
   uint32_t flags = FPDF_GetFieldAttr(pAnnotDict, "Ff")
                        ? FPDF_GetFieldAttr(pAnnotDict, "Ff")->GetInteger()
                        : 0;
@@ skipping 38 matching lines @@
 }
 
 bool CPVT_GenerateAP::GenerateHighlightAP(CPDF_Document* pDoc,
                                           CPDF_Dictionary* pAnnotDict) {
   // If AP dictionary exists, we use the appearance defined in the
   // existing AP dictionary.
   if (pAnnotDict->KeyExist("AP"))
     return false;
 
   CFX_ByteTextBuf sAppStream;
-  sAppStream << "/GS gs ";
+  CFX_ByteString sExtGSDictName = "GS";
+  sAppStream << "/" << sExtGSDictName << " gs ";
 
   if (pAnnotDict->KeyExist("C")) {
     CPDF_Array* pColor = pAnnotDict->GetArrayBy("C");
     CPVT_Color color = CPVT_Color::ParseColor(*pColor);
     sAppStream << CPVT_GenerateAP::GenerateColorAP(color, TRUE);
   } else {
     // Defaults to 0xFFFF00 color for highlight.
     sAppStream << "1 1 0 rg \n";
   }
 
@@ skipping 14 matching lines @@
 
   pNormalStream->SetData(reinterpret_cast<uint8_t*>(sAppStream.GetBuffer()),
                          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);
-  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);
+  FX_FLOAT fCAForStroke =
+      pAnnotDict->KeyExist("CA") ? pAnnotDict->GetNumberBy("CA") : 1.0;
+  FX_FLOAT fCAForNonStroke =
+      pAnnotDict->KeyExist("ca") ? pAnnotDict->GetNumberBy("ca") : 1.0;

[jaepark, 2016/08/01 23:10:52]

Although I think this is correct implementation, other PDF viewers (including
Adobe Acrobat Reader), are only depending on the value of "CA" to determine the
opacity of the annotation. 

For example, for highlight annotation, if CA is 1.0 and ca is 0.5, I think the
opacity should be 0.5 since Highlight is fill (non stroke) operation. However,
Acrobat Reader shows 1.0 opacity.

Also, Okular does not generate "ca" field when creating Highlight annotation (it
only generates "CA" field).

I'm not sure if I'm misinterpreting the spec of CA and ca in ExtGState (SECTION
4.3.4 Graphics State Parameter Dictionaries, TABLE 4.8 Entries in a graphics
state parameter dictionary).

[Lei Zhang, 2016/08/01 23:16:24]

Have you considered adding more tests to exercise this code and see what the
correct output should be?

You can write your own PDFs by hand. Take a look at testing/resources/*.in, and
testing/tools/fixup_pdf_template.py.

+  pResourceDict->SetAt("ExtGState",
+                       GenerateExtGStateDict(sExtGSDictName, fCAForStroke,
+                                             fCAForNonStroke, "Multiply"));
 
   pStreamDict->SetAt("Resources", pResourceDict);
   return true;
+}
+
+bool CPVT_GenerateAP::GenerateUnderlineAP(CPDF_Document* pDoc,
+                                          CPDF_Dictionary* pAnnotDict) {
+  // If AP dictionary exists, we use the appearance defined in the
+  // existing AP dictionary.
+  if (pAnnotDict->KeyExist("AP"))
+    return false;
+
+  CFX_ByteTextBuf sAppStream;
+  CFX_ByteString sExtGSDictName = "GS";
+  sAppStream << "/" << sExtGSDictName << " gs ";
+
+  if (pAnnotDict->KeyExist("C")) {
+    CPDF_Array* pColor = pAnnotDict->GetArrayBy("C");
+    CPVT_Color color = CPVT_Color::ParseColor(*pColor);
+    sAppStream << CPVT_GenerateAP::GenerateColorAP(color, FALSE);
+  } else {
+    // Defaults to 0x000000 color for underline.
+    sAppStream << "0 0 0 RG\n";
+  }
+
+  CFX_FloatRect rect = pAnnotDict->GetRectBy("Rect");
+  rect.Normalize();
+
+  FX_FLOAT fLineWidth = 1.0;
+  sAppStream << fLineWidth << " w " << rect.left << " "
+             << rect.bottom + fLineWidth << " m " << rect.right << " "
+             << rect.bottom + fLineWidth << " l S\n";
+
+  CPDF_Dictionary* pAPDict = new CPDF_Dictionary;
+  pAnnotDict->SetAt("AP", pAPDict);
+
+  CPDF_Stream* pNormalStream = new CPDF_Stream(nullptr, 0, nullptr);
+  int32_t objnum = pDoc->AddIndirectObject(pNormalStream);
+  pAnnotDict->GetDictBy("AP")->SetAtReference("N", pDoc, objnum);
+
+  pNormalStream->SetData(reinterpret_cast<uint8_t*>(sAppStream.GetBuffer()),
+                         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* pResourceDict = new CPDF_Dictionary;
+  FX_FLOAT fCAForStroke =
+      pAnnotDict->KeyExist("CA") ? pAnnotDict->GetNumberBy("CA") : 1.0;
+  FX_FLOAT fCAForNonStroke =
+      pAnnotDict->KeyExist("ca") ? pAnnotDict->GetNumberBy("ca") : 1.0;
+  pResourceDict->SetAt("ExtGState",
+                       GenerateExtGStateDict(sExtGSDictName, fCAForStroke,
+                                             fCAForNonStroke, "Normal"));
+
+  pStreamDict->SetAt("Resources", pResourceDict);
+  return true;
 }
 
 // Static.
 CFX_ByteString CPVT_GenerateAP::GenerateEditAP(
     IPVT_FontMap* pFontMap,
     CPDF_VariableText::Iterator* pIterator,
     const CFX_FloatPoint& ptOffset,
     FX_BOOL bContinuous,
     uint16_t SubWord) {
   CFX_ByteTextBuf sEditStream;
@@ skipping 247 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();
 }