Use rounding when converting desiredScale to a sampleSize

src/codec/SkScaledCodec.cpp

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkCodecPriv.h"
 #include "SkScaledCodec.h"
 #include "SkStream.h"
@@ skipping 69 matching lines @@
 SkISize SkScaledCodec::onGetScaledDimensions(float desiredScale) const {
     SkISize nativeDimensions = fScanlineDecoder->getScaledDimensions(desiredScale);
     // support scaling down by integer numbers. Ex: 1/2, 1/3, 1/4 ...
     SkISize scaledCodecDimensions;
     if (desiredScale > 0.5f) {
         // sampleSize = 1
         scaledCodecDimensions = fScanlineDecoder->getInfo().dimensions();
     }
     // sampleSize determines the step size between samples
     // Ex: sampleSize = 2, sample every second pixel in x and y directions
-    int sampleSize = int(1 / desiredScale);
+    int sampleSize = int ((1.0f / desiredScale) + 0.5f);
 
     int scaledWidth = get_scaled_dimension(this->getInfo().width(), sampleSize);
     int scaledHeight = get_scaled_dimension(this->getInfo().height(), sampleSize);
 
     // Return the calculated output dimensions for the given scale
     scaledCodecDimensions = SkISize::Make(scaledWidth, scaledHeight);
 
     return best_scaled_dimensions(this->getInfo().dimensions(), nativeDimensions,
                                   scaledCodecDimensions, desiredScale);
 }
@@ skipping 188 matching lines @@
                 storagePtr += sampleY * rowBytes;
                 dst = SkTAddOffset<void>(dst, rowBytes);
             }
             return result;
         }
         default:
             SkASSERT(false);
             return kUnimplemented;
     }
 }