Only call shading code with streams.

There are 4 types of meshes that attempt to convert the shading object into
a stream. According to spec (section 8.7.4.1 table 76), the shading object can
be a stream or a dictionary.

All of this shading code assumes it can load the mesh from a stream. The
original code just early exited if it was not a stream. We skip the call
if it is not a stream.

BUG=pdfium:481

Review URL: https://codereview.chromium.org/1908903003

1 files changed, 20 insertions, 10 deletions

diff --git a/core/fpdfapi/fpdf_render/fpdf_render_pattern.cpp b/core/fpdfapi/fpdf_render/fpdf_render_pattern.cpp
index 6ac380e43a..c235fd98cb 100644
--- a/core/fpdfapi/fpdf_render/fpdf_render_pattern.cpp
+++ b/core/fpdfapi/fpdf_render/fpdf_render_pattern.cpp
@@ -889,21 +889,31 @@ void CPDF_RenderStatus::DrawShading(CPDF_ShadingPattern* pPattern,
                         pColorSpace, alpha);
       break;
     case kFreeFormGouraudTriangleMeshShading: {
-      DrawFreeGouraudShading(pBitmap, &FinalMatrix,
-                             ToStream(pPattern->m_pShadingObj), pFuncs, nFuncs,
-                             pColorSpace, alpha);
+      // The shading object can be a stream or a dictionary. We do not handle
+      // the case of dictionary at the moment.
+      if (CPDF_Stream* pStream = ToStream(pPattern->m_pShadingObj)) {
+        DrawFreeGouraudShading(pBitmap, &FinalMatrix, pStream, pFuncs, nFuncs,
+                               pColorSpace, alpha);
+      }
     } break;
     case kLatticeFormGouraudTriangleMeshShading: {
-      DrawLatticeGouraudShading(pBitmap, &FinalMatrix,
-                                ToStream(pPattern->m_pShadingObj), pFuncs,
-                                nFuncs, pColorSpace, alpha);
+      // The shading object can be a stream or a dictionary. We do not handle
+      // the case of dictionary at the moment.
+      if (CPDF_Stream* pStream = ToStream(pPattern->m_pShadingObj)) {
+        DrawLatticeGouraudShading(pBitmap, &FinalMatrix, pStream, pFuncs,
+                                  nFuncs, pColorSpace, alpha);
+      }
     } break;
     case kCoonsPatchMeshShading:
     case kTensorProductPatchMeshShading: {
-      DrawCoonPatchMeshes(
-          pPattern->m_ShadingType == kTensorProductPatchMeshShading, pBitmap,
-          &FinalMatrix, ToStream(pPattern->m_pShadingObj), pFuncs, nFuncs,
-          pColorSpace, fill_mode, alpha);
+      // The shading object can be a stream or a dictionary. We do not handle
+      // the case of dictionary at the moment.
+      if (CPDF_Stream* pStream = ToStream(pPattern->m_pShadingObj)) {
+        DrawCoonPatchMeshes(
+            pPattern->m_ShadingType == kTensorProductPatchMeshShading, pBitmap,
+            &FinalMatrix, pStream, pFuncs, nFuncs, pColorSpace, fill_mode,
+            alpha);
+      }
     } break;
   }
   if (bAlphaMode) {