Use threshold of 1 texture coord value per pixel w/ nearest neighbor.

src/effects/SkArithmeticMode.cpp

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkArithmeticMode.h"
 #include "SkColorPriv.h"
 #include "SkReadBuffer.h"
@@ skipping 297 matching lines @@
 
 };
 
 ///////////////////////////////////////////////////////////////////////////////
 
 GrArithmeticEffect::GrArithmeticEffect(float k1, float k2, float k3, float k4,
                                        bool enforcePMColor, GrTexture* background)
   : fK1(k1), fK2(k2), fK3(k3), fK4(k4), fEnforcePMColor(enforcePMColor) {
     this->initClassID<GrArithmeticEffect>();
     if (background) {
-        fBackgroundTransform.reset(kLocal_GrCoordSet, background);
+        fBackgroundTransform.reset(kLocal_GrCoordSet, background,
+                                   GrTextureParams::kNone_FilterMode);
         this->addCoordTransform(&fBackgroundTransform);
         fBackgroundAccess.reset(background);
         this->addTextureAccess(&fBackgroundAccess);
     } else {
         this->setWillReadDstColor();
     }
 }
 
 GrArithmeticEffect::~GrArithmeticEffect() {
 }
@@ skipping 113 matching lines @@
                                          background);
     }
     return true;
 }
 
 #endif
 
 SK_DEFINE_FLATTENABLE_REGISTRAR_GROUP_START(SkArithmeticMode)
     SK_DEFINE_FLATTENABLE_REGISTRAR_ENTRY(SkArithmeticMode_scalar)
 SK_DEFINE_FLATTENABLE_REGISTRAR_GROUP_END