Exclude certain colorspace types for calculating transparency backdrop color.

Per discussion for the "CS" entry in the PDF 1.7 spec table 7.13, several
types of colorspaces do not meet the requirements of this particular
colorspace entry. In terms of implementation, this avoids hitting a
NOTREACHED() in CPDF_PatternCS::GetRGB().

BUG=chromium:847346

Change-Id: If994a91cdcd84b8977196256ee6926e20c4b74aa
Reviewed-on: https://pdfium-review.googlesource.com/33210
Reviewed-by: Henrique Nakashima <hnakashima@chromium.org>
Commit-Queue: Lei Zhang <thestig@chromium.org>

1 files changed, 7 insertions, 5 deletions

diff --git a/core/fpdfapi/render/cpdf_renderstatus.cpp b/core/fpdfapi/render/cpdf_renderstatus.cpp
index d63d321b9f..af976903be 100644
--- a/core/fpdfapi/render/cpdf_renderstatus.cpp
+++ b/core/fpdfapi/render/cpdf_renderstatus.cpp
@@ -2646,17 +2646,19 @@ FX_ARGB CPDF_RenderStatus::GetBackColor(const CPDF_Dictionary* pSMaskDict,
   const CPDF_Object* pCSObj = nullptr;
   const CPDF_Dictionary* pGroup =
       pGroupDict ? pGroupDict->GetDictFor("Group") : nullptr;
-  if (pGroup) {
-    // TODO(thestig): Check if "CS" is from PDF spec 1.7, table 13.
-    pCSObj = pGroup->GetDirectObjectFor("CS");
-  }
+  if (pGroup)
+    pCSObj = pGroup->GetDirectObjectFor(pdfium::transparency::kCS);
   const CPDF_ColorSpace* pCS =
       m_pContext->GetDocument()->LoadColorSpace(pCSObj);
   if (!pCS)
     return kDefaultColor;
 
+  int family = pCS->GetFamily();
+  if (family == PDFCS_LAB || family == PDFCS_ICCBASED || pCS->IsSpecial())
+    return kDefaultColor;
+
   // Store Color Space Family to use in CPDF_RenderStatus::Initialize().
-  *pCSFamily = pCS->GetFamily();
+  *pCSFamily = family;
 
   uint32_t comps = std::max(8u, pCS->CountComponents());
   std::vector<float> floats(comps);