Fixes for unpremul decode.

tests/ImageDecodingTest.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 "SkBitmap.h"
 #include "SkColorPriv.h"
 #include "SkForceLinking.h"
@@ skipping 105 matching lines @@
             // bitmap at (i, j).
             const SkPMColor c1 = premultiply_unpmcolor(*bm8888Unpremul.getAddr32(i, j));
             // Compute the difference for each component.
             int da = SkAbs32(SkGetPackedA32(c0) - SkGetPackedA32(c1));
             int dr = SkAbs32(SkGetPackedR32(c0) - SkGetPackedR32(c1));
             int dg = SkAbs32(SkGetPackedG32(c0) - SkGetPackedG32(c1));
             int db = SkAbs32(SkGetPackedB32(c0) - SkGetPackedB32(c1));
 
             // Alpha component must be exactly the same.
             REPORTER_ASSERT(reporter, 0 == da);
-            // Other components may differ if rounding is done differently,
-            // but currently that is not the case. If an image fails here
-            // in the future, we can change these to account for differences.
-            REPORTER_ASSERT(reporter, 0 == dr);
-            REPORTER_ASSERT(reporter, 0 == dg);
-            REPORTER_ASSERT(reporter, 0 == db);
+
+            // Color components may not match exactly due to rounding error.
+            REPORTER_ASSERT(reporter, dr <= 1);
+            REPORTER_ASSERT(reporter, dg <= 1);
+            REPORTER_ASSERT(reporter, db <= 1);
         }
     }
 }
 
 static void test_imageDecodingTests(skiatest::Reporter* reporter) {
     // This test cannot run if there is no resource path.
     SkString resourcePath = skiatest::Test::GetResourcePath();
     if (resourcePath.isEmpty()) {
         return;
     }
     SkOSFile::Iter iter(resourcePath.c_str());
     SkString basename;
     if (iter.next(&basename)) {
         do {
             SkString filename = SkOSPath::SkPathJoin(resourcePath.c_str(), basename.c_str());
             //SkDebugf("about to decode \"%s\"\n", filename.c_str());
             compare_unpremul(reporter, filename);
         } while (iter.next(&basename));
     } else {
         SkDebugf("Failed to find any files :(\n");
     }
 }
 
 #include "TestClassDef.h"
 DEFINE_TESTCLASS("ImageDecoding", ImageDecodingTestClass,
                  test_imageDecodingTests)