commit 20e0243386f62093477b69979c00e7ce60e99938
author Hui Yingst <nigi@chromium.org> Tue Jun 11 20:51:40 2019 +0000
committer Chromium commit bot <commit-bot@chromium.org> Tue Jun 11 20:51:40 2019 +0000
tree 2368e10cd35077557c2a9d6333175baa2a512df1
parent b6fd8a85e7fdc549e11fd7210321c3a56d4fadfe

[SkiaPath] Fix broken gradient transition.

Skia Path wasn't handling the case when encode pairs in stitch function
have decreasing order. To fix this, add comparison for each pair of
encode values and reverse the order of |skColors| array accordingly.

Bug: pdfium:842
Change-Id: I51fc0243d25bc1adee3ee3061d3db658c8f84e94
Reviewed-on: https://pdfium-review.googlesource.com/c/pdfium/+/55712
Commit-Queue: Lei Zhang <thestig@chromium.org>
Reviewed-by: Lei Zhang <thestig@chromium.org>

core/fpdfapi/page/cpdf_stitchfunc.h

diff --git a/core/fpdfapi/page/cpdf_stitchfunc.h b/core/fpdfapi/page/cpdf_stitchfunc.h
index 022bd4e..761c9ba 100644
--- a/core/fpdfapi/page/cpdf_stitchfunc.h
+++ b/core/fpdfapi/page/cpdf_stitchfunc.h
@@ -27,6 +27,7 @@
     return m_pSubFunctions;
   }
   float GetBound(size_t i) const { return m_bounds[i]; }
+  float GetEncode(size_t i) const { return m_encode[i]; }
 
  private:
   std::vector<std::unique_ptr<CPDF_Function>> m_pSubFunctions;

core/fxge/skia/fx_skia_device.cpp

diff --git a/core/fxge/skia/fx_skia_device.cpp b/core/fxge/skia/fx_skia_device.cpp
index 21f3b31..dfdaff6 100644
--- a/core/fxge/skia/fx_skia_device.cpp
+++ b/core/fxge/skia/fx_skia_device.cpp
@@ -375,21 +375,34 @@
   }
 }
 
-bool AddColors(const CPDF_ExpIntFunc* pFunc, SkTDArray<SkColor>* skColors) {
+// Add begin & end colors into |skColors| array for each gradient transition.
+//
+// |is_encode_reversed| must be set to true when the parent function of |pFunc|
+// has an Encode array, and the matching pair of encode values for |pFunc| are
+// in decreasing order.
+bool AddColors(const CPDF_ExpIntFunc* pFunc,
+               SkTDArray<SkColor>* skColors,
+               bool is_encode_reversed) {
   if (pFunc->CountInputs() != 1)
     return false;
   if (pFunc->m_Exponent != 1)
     return false;
   if (pFunc->m_nOrigOutputs != 3)
     return false;
-  skColors->push_back(
-      SkColorSetARGB(0xFF, SkUnitScalarClampToByte(pFunc->m_BeginValues[0]),
-                     SkUnitScalarClampToByte(pFunc->m_BeginValues[1]),
-                     SkUnitScalarClampToByte(pFunc->m_BeginValues[2])));
-  skColors->push_back(
-      SkColorSetARGB(0xFF, SkUnitScalarClampToByte(pFunc->m_EndValues[0]),
-                     SkUnitScalarClampToByte(pFunc->m_EndValues[1]),
-                     SkUnitScalarClampToByte(pFunc->m_EndValues[2])));
+
+  auto begin_values = pFunc->m_BeginValues.begin();
+  auto end_values = pFunc->m_EndValues.begin();
+  if (is_encode_reversed)
+    std::swap(begin_values, end_values);
+
+  skColors->push_back(SkColorSetARGB(0xFF,
+                                     SkUnitScalarClampToByte(begin_values[0]),
+                                     SkUnitScalarClampToByte(begin_values[1]),
+                                     SkUnitScalarClampToByte(begin_values[2])));
+  skColors->push_back(SkColorSetARGB(0xFF,
+                                     SkUnitScalarClampToByte(end_values[0]),
+                                     SkUnitScalarClampToByte(end_values[1]),
+                                     SkUnitScalarClampToByte(end_values[2])));
   return true;
 }
 
@@ -456,7 +469,10 @@
     const CPDF_ExpIntFunc* pSubFunc = subFunctions[i]->ToExpIntFunc();
     if (!pSubFunc)
       return false;
-    if (!AddColors(pSubFunc, skColors))
+    // Check if the matching encode values are reversed
+    bool is_encode_reversed =
+        pFunc->GetEncode(2 * i) > pFunc->GetEncode(2 * i + 1);
+    if (!AddColors(pSubFunc, skColors, is_encode_reversed))
       return false;
     float boundsEnd =
         i < subFunctionCount - 1 ? pFunc->GetBound(i + 1) : pFunc->GetDomain(1);
@@ -2025,7 +2041,7 @@
       if (!AddSamples(pSampledFunc, &skColors, &skPos))
         return false;
     } else if (const CPDF_ExpIntFunc* pExpIntFuc = pFuncs[j]->ToExpIntFunc()) {
-      if (!AddColors(pExpIntFuc, &skColors))
+      if (!AddColors(pExpIntFuc, &skColors, /*is_encode_reversed=*/false))
         return false;
       skPos.push_back(0);
       skPos.push_back(1);