Manually set fFilterValues in SkConvolutionFilter1D.

src/core/SkConvolver.cpp

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "SkConvolver.h"
 #include "SkSize.h"
 #include "SkTypes.h"
 
 namespace {
 
@@ skipping 265 matching lines @@
     // It is common for leading/trailing filter values to be zeros. In such
     // cases it is beneficial to only store the central factors.
     // For a scaling to 1/4th in each dimension using a Lanczos-2 filter on
     // a 1080p image this optimization gives a ~10% speed improvement.
     int filterSize = filterLength;
     int firstNonZero = 0;
     while (firstNonZero < filterLength && filterValues[firstNonZero] == 0) {
         firstNonZero++;
     }
 
+    int initialOffset = fFilterValues.count();
     if (firstNonZero < filterLength) {
         // Here we have at least one non-zero factor.
         int lastNonZero = filterLength - 1;
         while (lastNonZero >= 0 && filterValues[lastNonZero] == 0) {
             lastNonZero--;
         }
 
         filterOffset += firstNonZero;
         filterLength = lastNonZero + 1 - firstNonZero;
         SkASSERT(filterLength > 0);
 
+        // Calling fFilterValues.reset(), or push_back() in a loop, are expensive.
+        // Over-allocate so we can do it once instead of iteratively.
+        if (!initialOffset) fFilterValues.resize_back(filterLength * filterLength);
         for (int i = firstNonZero; i <= lastNonZero; i++) {
-            fFilterValues.push_back(filterValues[i]);
+            fFilterValues[initialOffset + i - firstNonZero] = filterValues[i];
         }
+
     } else {
         // Here all the factors were zeroes.
         filterLength = 0;
     }
 
     FilterInstance instance;
 
     // We pushed filterLength elements onto fFilterValues
     instance.fDataLocation = (static_cast<int>(fFilterValues.count()) -
                                                filterLength);
@@ skipping 142 matching lines @@
                                                filterX.numValues(), curOutputRow,
                                                sourceHasAlpha);
         } else {
             ConvolveVertically(filterValues, filterLength,
                                firstRowForFilter,
                                filterX.numValues(), curOutputRow,
                                sourceHasAlpha);
         }
     }
 }