Merge remote-tracking branch 'upstream/pr/521' into develop

Pentax K-3 Mark III Monochrome DNG bug.

* upstream/pr/521:
  Relax DNG black level parsing

src/librawspeed/decoders/DngDecoder.cpp

@@ -767,9 +767,16 @@ bool DngDecoder::decodeBlackLevels(const TiffIFD* raw) const {
   iPoint2D blackdim(1, 1);
   if (raw->hasEntry(TiffTag::BLACKLEVELREPEATDIM)) {
     const TiffEntry* bleveldim = raw->getEntry(TiffTag::BLACKLEVELREPEATDIM);
-    if (bleveldim->count != 2)
+    if (bleveldim->count == 2)
+      blackdim = iPoint2D(bleveldim->getU32(0), bleveldim->getU32(1));
+    else if (bleveldim->count == 1) {
+      // Non-spec-compliant quirk. Assuming NxN repeat dimensions.
+      blackdim = iPoint2D(bleveldim->getU32(0), bleveldim->getU32(0));
+      // Let's only allow somewhat unambiguous case of 1x1 repeat dimensions.
+      if (blackdim != iPoint2D(1, 1))
+        return false;
+    } else
       return false;
-    blackdim = iPoint2D(bleveldim->getU32(0), bleveldim->getU32(1));
   }
 
   if (!blackdim.hasPositiveArea())