Add constants for PDF 1.7 spec, table 7.13.

BUG=pdfium:1049

Change-Id: I3a589fe51f2e584dc130ba31faa144d4494a1b08
Reviewed-on: https://pdfium-review.googlesource.com/32179
Commit-Queue: Lei Zhang <thestig@chromium.org>
Reviewed-by: dsinclair <dsinclair@chromium.org>

3 files changed, 32 insertions, 11 deletions

diff --git a/constants/transparency.h b/constants/transparency.h
index 6ae79c949d..22a89c33c4 100644
--- a/constants/transparency.h
+++ b/constants/transparency.h
@@ -32,6 +32,22 @@ constexpr char kSaturation[] = "Saturation";
 constexpr char kColor[] = "Color";
 constexpr char kLuminosity[] = "Luminosity";
 
+// PDF 1.7 spec, table 7.10.
+// Entries in a soft-mask dictionary.
+
+constexpr char kSoftMaskSubType[] = "S";
+constexpr char kAlpha[] = "Alpha";
+constexpr char kG[] = "G";
+constexpr char kBC[] = "BC";
+constexpr char kTR[] = "TR";
+
+// PDF 1.7 spec, table 7.13.
+// Additional entries specific to a transparency group attributes dictionary.
+
+constexpr char kGroupSubType[] = "S";
+constexpr char kTransparency[] = "Transparency";
+constexpr char kI[] = "I";
+
 }  // namespace transparency
 }  // namespace pdfium
 
diff --git a/core/fpdfapi/page/cpdf_pageobjectholder.cpp b/core/fpdfapi/page/cpdf_pageobjectholder.cpp
index 3c998d2424..d8858279ca 100644
--- a/core/fpdfapi/page/cpdf_pageobjectholder.cpp
+++ b/core/fpdfapi/page/cpdf_pageobjectholder.cpp
@@ -9,6 +9,7 @@
 #include <algorithm>
 #include <utility>
 
+#include "constants/transparency.h"
 #include "core/fpdfapi/page/cpdf_allstates.h"
 #include "core/fpdfapi/page/cpdf_contentparser.h"
 #include "core/fpdfapi/page/cpdf_pageobject.h"
@@ -69,20 +70,20 @@ CFX_FloatRect CPDF_PageObjectHolder::CalcBoundingBox() const {
 }
 
 void CPDF_PageObjectHolder::LoadTransInfo() {
-  if (!m_pFormDict) {
+  if (!m_pFormDict)
     return;
-  }
+
   CPDF_Dictionary* pGroup = m_pFormDict->GetDictFor("Group");
-  if (!pGroup) {
+  if (!pGroup)
     return;
-  }
-  if (pGroup->GetStringFor("S") != "Transparency") {
+
+  if (pGroup->GetStringFor(pdfium::transparency::kGroupSubType) !=
+      pdfium::transparency::kTransparency) {
     return;
   }
   m_iTransparency |= PDFTRANS_GROUP;
-  if (pGroup->GetIntegerFor("I")) {
+  if (pGroup->GetIntegerFor(pdfium::transparency::kI))
     m_iTransparency |= PDFTRANS_ISOLATED;
-  }
 }
 
 size_t CPDF_PageObjectHolder::GetPageObjectCount() const {
diff --git a/core/fpdfapi/render/cpdf_renderstatus.cpp b/core/fpdfapi/render/cpdf_renderstatus.cpp
index 3672729f2e..0f054ef578 100644
--- a/core/fpdfapi/render/cpdf_renderstatus.cpp
+++ b/core/fpdfapi/render/cpdf_renderstatus.cpp
@@ -13,6 +13,7 @@
 #include <utility>
 #include <vector>
 
+#include "constants/transparency.h"
 #include "core/fpdfapi/font/cpdf_font.h"
 #include "core/fpdfapi/font/cpdf_type3char.h"
 #include "core/fpdfapi/font/cpdf_type3font.h"
@@ -2530,12 +2531,13 @@ RetainPtr<CFX_DIBitmap> CPDF_RenderStatus::LoadSMask(
   if (!pSMaskDict)
     return nullptr;
 
-  CPDF_Stream* pGroup = pSMaskDict->GetStreamFor("G");
+  CPDF_Stream* pGroup = pSMaskDict->GetStreamFor(pdfium::transparency::kG);
   if (!pGroup)
     return nullptr;
 
   std::unique_ptr<CPDF_Function> pFunc;
-  CPDF_Object* pFuncObj = pSMaskDict->GetDirectObjectFor("TR");
+  CPDF_Object* pFuncObj =
+      pSMaskDict->GetDirectObjectFor(pdfium::transparency::kTR);
   if (pFuncObj && (pFuncObj->IsDictionary() || pFuncObj->IsStream()))
     pFunc = CPDF_Function::Load(pFuncObj);
 
@@ -2547,7 +2549,9 @@ RetainPtr<CFX_DIBitmap> CPDF_RenderStatus::LoadSMask(
   form.ParseContent();
 
   CFX_DefaultRenderDevice bitmap_device;
-  bool bLuminosity = pSMaskDict->GetStringFor("S") != "Alpha";
+  bool bLuminosity =
+      pSMaskDict->GetStringFor(pdfium::transparency::kSoftMaskSubType) !=
+      pdfium::transparency::kAlpha;
   int width = pClipRect->right - pClipRect->left;
   int height = pClipRect->bottom - pClipRect->top;
   FXDIB_Format format;
@@ -2629,7 +2633,7 @@ FX_ARGB CPDF_RenderStatus::GetBackColor(const CPDF_Dictionary* pSMaskDict,
                                         const CPDF_Dictionary* pGroupDict,
                                         int* pCSFamily) {
   static constexpr FX_ARGB kDefaultColor = ArgbEncode(255, 0, 0, 0);
-  CPDF_Array* pBC = pSMaskDict->GetArrayFor("BC");
+  const CPDF_Array* pBC = pSMaskDict->GetArrayFor(pdfium::transparency::kBC);
   if (!pBC)
     return kDefaultColor;