Revert "Revert "Experimental blur code with 32 bit fix.""

This reverts commit 27b3d272a8fcce24813212f5816b177090111ec6.

Reason for revert: guard has landed in android

Original change's description:
> Revert "Experimental blur code with 32 bit fix."
> 
> This reverts commit d4b2c537d058ad4cb890ba116d00aa86c3416c08.
> 
> Reason for revert: speculative fix for android-roll
> 
> java.lang.AssertionError: expected:<0> but was:<255>
> at org.junit.Assert.fail(Assert.java:88)
> at org.junit.Assert.failNotEquals(Assert.java:834)
> at org.junit.Assert.assertEquals(Assert.java:645)
> at org.junit.Assert.assertEquals(Assert.java:631)
> at android.graphics.cts.BlurMaskFilterTest.verifyColor(BlurMaskFilterTest.java:79)
> at android.graphics.cts.BlurMaskFilterTest.verifyQuadrants(BlurMaskFilterTest.java:72)
> at android.graphics.cts.BlurMaskFilterTest.testBlurMaskFilter(BlurMaskFilterTest.java:56)
> 
> Original change's description:
> > Experimental blur code with 32 bit fix.
> > 
> > This uses a new method of blurring that runs the three
> > passes of the box filter in a single pass. This implementation
> > currently only does 1x1 pixel at a time, but it should be simple
> > to expand to 4x4 pixels at a time.
> > 
> > On the  blur_10_normal_high_quality benchmark, the new is 7% faster
> > than the old code. For the blur_100.50_normal_high_quality
> > benchmark, the new code is 11% slower.
> > 
> > Bug: skia:
> > Change-Id: I847270906b0ceac1dfbf43ab5446756689ef660f
> > Reviewed-on: https://skia-review.googlesource.com/22700
> > Reviewed-by: Mike Reed <reed@google.com>
> > Commit-Queue: Herb Derby <herb@google.com>
> 
> TBR=herb@google.com,reed@google.com
> 
> Change-Id: Ie84f6bf8872cae08c06d679f0c2f2e6c3d8a02a2
> No-Presubmit: true
> No-Tree-Checks: true
> No-Try: true
> Bug: skia:
> Reviewed-on: https://skia-review.googlesource.com/22880
> Reviewed-by: Mike Reed <reed@google.com>
> Commit-Queue: Mike Reed <reed@google.com>

TBR=herb@google.com,reed@google.com

Change-Id: I393d1c05f83ccf98137201bc7b4e7d8e8b0e8742
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: skia:
Reviewed-on: https://skia-review.googlesource.com/23121
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Mike Reed <reed@google.com>

1 files changed, 67 insertions, 0 deletions

diff --git a/src/core/SkMaskBlurFilter.h b/src/core/SkMaskBlurFilter.h
new file mode 100644
index 0000000000..9becadca39
--- /dev/null
+++ b/src/core/SkMaskBlurFilter.h
@@ -0,0 +1,67 @@
+/*
+ * Copyright 2017 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef SkBlurMaskFilter_DEFINED
+#define SkBlurMaskFilter_DEFINED
+
+#include <algorithm>
+#include <memory>
+
+#include "SkMask.h"
+#include "SkTypes.h"
+
+// Implement a single channel Gaussian blur. The specifics for implementation are taken from:
+// https://drafts.fxtf.org/filters/#feGaussianBlurElement
+class SkMaskBlurFilter {
+public:
+    // Given a filter specified by sigma, generate various quantities.
+    class FilterInfo {
+    public:
+        explicit FilterInfo(double sigma);
+
+        // The final weight to divide by given a box size calculated from sigma accumulated for
+        // all three passes. For example, if the box size is 5, then the final weight for all
+        // three passes is 5^3 or 125.
+        uint64_t weight() const;
+
+        // The distance between the first value of the dst and the first value of the src.
+        uint32_t borderSize() const;
+
+        // The size of the box filter.
+        size_t   diameter(uint8_t) const;
+
+        // A factor used to simulate division using multiplication and shift.
+        uint64_t scaledWeight() const;
+
+    private:
+        const uint32_t fFilterWindow;
+        const uint64_t fScaledWeight;
+    };
+
+    // Create an object suitable for filtering an SkMask using a filter with width sigmaW and
+    // height sigmaH.
+    SkMaskBlurFilter(double sigmaW, double sigmaH);
+
+    // Given a src SkMask, generate dst SkMask returning the border width and height.
+    SkIPoint blur(const SkMask& src, SkMask* dst) const;
+
+private:
+    size_t bufferSize(uint8_t bufferPass) const;
+
+    void blurOneScan(FilterInfo gen,
+                     const uint8_t* src, size_t srcStride, const uint8_t* srcEnd,
+                           uint8_t* dst, size_t dstStride,       uint8_t* dstEnd) const;
+
+
+    const FilterInfo            fInfoW,
+                                fInfoH;
+    std::unique_ptr<uint32_t[]> fBuffer0,
+                                fBuffer1,
+                                fBuffer2;
+};
+
+#endif  // SkBlurMaskFilter_DEFINED