Add constants for PDF 1.7 spec, table 7.2 and 7.3.

Add constants/transparency.h. The header lists constants from chapter 7
of the PDF spec.

BUG=pdfium:1049

Change-Id: I66bd6fceb24807eec9c308e2e47cec3f2f836ffb
Reviewed-on: https://pdfium-review.googlesource.com/32177
Reviewed-by: dsinclair <dsinclair@chromium.org>
Commit-Queue: Lei Zhang <thestig@chromium.org>

3 files changed, 59 insertions, 18 deletions

diff --git a/BUILD.gn b/BUILD.gn
index fc7c0eed8b..874a8f7d81 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -300,6 +300,7 @@ visibility = [
 source_set("constants") {
   sources = [
     "constants/stream_dict_common.h",
+    "constants/transparency.h",
   ]
 }
 
diff --git a/constants/transparency.h b/constants/transparency.h
new file mode 100644
index 0000000000..6ae79c949d
--- /dev/null
+++ b/constants/transparency.h
@@ -0,0 +1,38 @@
+// Copyright 2018 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.
+
+#ifndef CONSTANTS_TRANSPARENCY_H_
+#define CONSTANTS_TRANSPARENCY_H_
+
+namespace pdfium {
+namespace transparency {
+
+// PDF 1.7 spec, table 7.2.
+// Standard separable blend modes.
+
+constexpr char kNormal[] = "Normal";
+constexpr char kMultiply[] = "Multiply";
+constexpr char kScreen[] = "Screen";
+constexpr char kOverlay[] = "Overlay";
+constexpr char kDarken[] = "Darken";
+constexpr char kLighten[] = "Lighten";
+constexpr char kColorDodge[] = "ColorDodge";
+constexpr char kColorBurn[] = "ColorBurn";
+constexpr char kHardLight[] = "HardLight";
+constexpr char kSoftLight[] = "SoftLight";
+constexpr char kDifference[] = "Difference";
+constexpr char kExclusion[] = "Exclusion";
+
+// PDF 1.7 spec, table 7.3.
+// Standard nonseparable blend modes.
+
+constexpr char kHue[] = "Hue";
+constexpr char kSaturation[] = "Saturation";
+constexpr char kColor[] = "Color";
+constexpr char kLuminosity[] = "Luminosity";
+
+}  // namespace transparency
+}  // namespace pdfium
+
+#endif  // CONSTANTS_TRANSPARENCY_H_
diff --git a/core/fpdfapi/page/cpdf_generalstate.cpp b/core/fpdfapi/page/cpdf_generalstate.cpp
index 845cedd496..a5b718bfff 100644
--- a/core/fpdfapi/page/cpdf_generalstate.cpp
+++ b/core/fpdfapi/page/cpdf_generalstate.cpp
@@ -6,6 +6,7 @@
 
 #include "core/fpdfapi/page/cpdf_generalstate.h"
 
+#include "constants/transparency.h"
 #include "core/fpdfapi/parser/cpdf_document.h"
 #include "core/fpdfapi/render/cpdf_dibsource.h"
 #include "core/fpdfapi/render/cpdf_docrenderdata.h"
@@ -78,42 +79,43 @@ CPDF_GeneralState::~CPDF_GeneralState() {}
 void CPDF_GeneralState::SetRenderIntent(const ByteString& ri) {
   m_Ref.GetPrivateCopy()->m_RenderIntent = RI_StringToId(ri);
 }
+
 ByteString CPDF_GeneralState::GetBlendMode() const {
   switch (GetBlendType()) {
     case FXDIB_BLEND_NORMAL:
-      return ByteString("Normal");
+      return ByteString(pdfium::transparency::kNormal);
     case FXDIB_BLEND_MULTIPLY:
-      return ByteString("Multiply");
+      return ByteString(pdfium::transparency::kMultiply);
     case FXDIB_BLEND_SCREEN:
-      return ByteString("Screen");
+      return ByteString(pdfium::transparency::kScreen);
     case FXDIB_BLEND_OVERLAY:
-      return ByteString("Overlay");
+      return ByteString(pdfium::transparency::kOverlay);
     case FXDIB_BLEND_DARKEN:
-      return ByteString("Darken");
+      return ByteString(pdfium::transparency::kDarken);
     case FXDIB_BLEND_LIGHTEN:
-      return ByteString("Lighten");
+      return ByteString(pdfium::transparency::kLighten);
     case FXDIB_BLEND_COLORDODGE:
-      return ByteString("ColorDodge");
+      return ByteString(pdfium::transparency::kColorDodge);
     case FXDIB_BLEND_COLORBURN:
-      return ByteString("ColorBurn");
+      return ByteString(pdfium::transparency::kColorBurn);
     case FXDIB_BLEND_HARDLIGHT:
-      return ByteString("HardLight");
+      return ByteString(pdfium::transparency::kHardLight);
     case FXDIB_BLEND_SOFTLIGHT:
-      return ByteString("SoftLight");
+      return ByteString(pdfium::transparency::kSoftLight);
     case FXDIB_BLEND_DIFFERENCE:
-      return ByteString("Difference");
+      return ByteString(pdfium::transparency::kDifference);
     case FXDIB_BLEND_EXCLUSION:
-      return ByteString("Exclusion");
+      return ByteString(pdfium::transparency::kExclusion);
     case FXDIB_BLEND_HUE:
-      return ByteString("Hue");
+      return ByteString(pdfium::transparency::kHue);
     case FXDIB_BLEND_SATURATION:
-      return ByteString("Saturation");
+      return ByteString(pdfium::transparency::kSaturation);
     case FXDIB_BLEND_COLOR:
-      return ByteString("Color");
+      return ByteString(pdfium::transparency::kColor);
     case FXDIB_BLEND_LUMINOSITY:
-      return ByteString("Luminosity");
+      return ByteString(pdfium::transparency::kLuminosity);
   }
-  return ByteString("Normal");
+  return ByteString(pdfium::transparency::kNormal);
 }
 
 int CPDF_GeneralState::GetBlendType() const {
@@ -258,7 +260,7 @@ CFX_Matrix* CPDF_GeneralState::GetMutableMatrix() {
 }
 
 CPDF_GeneralState::StateData::StateData()
-    : m_BlendMode("Normal"),
+    : m_BlendMode(pdfium::transparency::kNormal),
       m_BlendType(0),
       m_pSoftMask(nullptr),
       m_StrokeAlpha(1.0),