Revert "reduce SkDisplacementImageFilter size"

This reverts commit ed68a92ca65762f0d0c4060668ceeb9c92506cf9.

Reason for revert: breaks layouttests (on BGRA?)

Original change's description:
> reduce SkDisplacementImageFilter size
> 
> saves ~8K on mac laptop
> 
> - remove templates
> - check for 0 0r 0xFF in alpha
> 
> Before: (using modified bench w/o caching)
> 
>   23/23  MB	2	134µs	151µs	146µs	156µs	6%	█▇▆▆▆▆▄▁▁▁	8888	displacement_full_large
>   23/23  MB	2	253µs	254µs	255µs	260µs	1%	█▄▄▅▂▁▂▁▁▁	8888	displacement_alpha_large
>   24/24  MB	1	410µs	410µs	415µs	445µs	3%	█▃▁▂▁▁▁▁▁▁	8888	displacement_zero_large
>   24/24  MB	151	840ns	841ns	853ns	938ns	4%	█▁▁▁▁▁▁▂▁▁	8888	displacement_full_small
>   24/24  MB	180	832ns	835ns	836ns	851ns	1%	█▂▁▂▂▁▂▂▂▂	8888	displacement_alpha_small
>   24/24  MB	9	60µs	60.9µs	69.9µs	101µs	19%	█▄▄▄▁▁▁▁▁▁	8888	displacement_zero_small
> 
> After:
> 
>   23/23  MB	3	47.4µs	48µs	48.2µs	51.4µs	2%	█▂▂▃▃▁▁▁▂▁	8888	displacement_full_large
>   23/23  MB	2	140µs	141µs	145µs	166µs	7%	▂▁▁▁▁▁▁▁▇█	8888	displacement_alpha_large
>   24/24  MB	2	189µs	196µs	197µs	225µs	5%	█▃▂▂▂▂▃▂▁▁	8888	displacement_zero_large
>   24/24  MB	134	588ns	594ns	597ns	616ns	1%	▂▁▁█▂▆▂▂▃▄	8888	displacement_full_small
>   24/24  MB	168	590ns	592ns	592ns	599ns	0%	▃▂▁▁▁▁▁█▂▂	8888	displacement_alpha_small
>   24/24  MB	9	8.39µs	8.41µs	8.42µs	8.53µs	0%	█▄▃▂▁▁▃▂▁▂	8888	displacement_zero_small
> 
> Bug: skia:
> Change-Id: Ia3b12dc8420b32b65633bb1cf76a15241e420eac
> Reviewed-on: https://skia-review.googlesource.com/20181
> Reviewed-by: Mike Klein <mtklein@google.com>
> Commit-Queue: Mike Reed <reed@google.com>

TBR=mtklein@google.com,robertphillips@google.com,fmalita@chromium.org,reed@google.com

Change-Id: I811c5f25a328c75527ce5caa0d9b8e123d535583
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: skia:
Reviewed-on: https://skia-review.googlesource.com/20182
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Mike Reed <reed@google.com>

1 files changed, 86 insertions, 35 deletions

diff --git a/src/effects/SkDisplacementMapEffect.cpp b/src/effects/SkDisplacementMapEffect.cpp
index 83f97b9353..82c2b59aca 100644
--- a/src/effects/SkDisplacementMapEffect.cpp
+++ b/src/effects/SkDisplacementMapEffect.cpp
@@ -33,41 +33,35 @@ namespace {
 
 #define kChannelSelectorKeyBits 3; // Max value is 4, so 3 bits are required at most
 
-const uint8_t gChannelTypeToShift[] = {
-     0,  // unknown
-    SK_RGBA_R32_SHIFT,
-    SK_RGBA_G32_SHIFT,
-    SK_RGBA_B32_SHIFT,
-    SK_RGBA_A32_SHIFT,
-};
-struct Extractor {
-    Extractor(SkDisplacementMapEffect::ChannelSelectorType typeX,
-              SkDisplacementMapEffect::ChannelSelectorType typeY)
-        : fShiftX(gChannelTypeToShift[typeX])
-        , fShiftY(gChannelTypeToShift[typeY])
-    {}
+template<SkDisplacementMapEffect::ChannelSelectorType type>
+uint32_t getValue(SkColor, const SkUnPreMultiply::Scale*) {
+    SkDEBUGFAIL("Unknown channel selector");
+    return 0;
+}
 
-    unsigned fShiftX, fShiftY;
+template<> uint32_t getValue<SkDisplacementMapEffect::kR_ChannelSelectorType>(
+    SkColor l, const SkUnPreMultiply::Scale* table) {
+    return SkUnPreMultiply::ApplyScale(table[SkGetPackedA32(l)], SkGetPackedR32(l));
+}
 
-    unsigned getX(SkPMColor c) const { return (c >> fShiftX) & 0xFF; }
-    unsigned getY(SkPMColor c) const { return (c >> fShiftY) & 0xFF; }
-};
+template<> uint32_t getValue<SkDisplacementMapEffect::kG_ChannelSelectorType>(
+    SkColor l, const SkUnPreMultiply::Scale* table) {
+    return SkUnPreMultiply::ApplyScale(table[SkGetPackedA32(l)], SkGetPackedG32(l));
+}
 
-static SkPMColor unpremul_pm(SkPMColor c) {
-    const U8CPU a = SkGetPackedA32(c);
-    if (0 == a) {
-        return 0;
-    } else if (0xFF == a) {
-        return c;
-    }
-    const unsigned scale = SkUnPreMultiply::GetScale(a);
-    return SkPackARGB32NoCheck(a,
-                               SkUnPreMultiply::ApplyScale(scale, SkGetPackedR32(c)),
-                               SkUnPreMultiply::ApplyScale(scale, SkGetPackedG32(c)),
-                               SkUnPreMultiply::ApplyScale(scale, SkGetPackedB32(c)));
+template<> uint32_t getValue<SkDisplacementMapEffect::kB_ChannelSelectorType>(
+    SkColor l, const SkUnPreMultiply::Scale* table) {
+    return SkUnPreMultiply::ApplyScale(table[SkGetPackedA32(l)], SkGetPackedB32(l));
 }
 
-void computeDisplacement(Extractor ex, const SkVector& scale, SkBitmap* dst,
+template<> uint32_t getValue<SkDisplacementMapEffect::kA_ChannelSelectorType>(
+    SkColor l, const SkUnPreMultiply::Scale*) {
+    return SkGetPackedA32(l);
+}
+
+template<SkDisplacementMapEffect::ChannelSelectorType typeX,
+         SkDisplacementMapEffect::ChannelSelectorType typeY>
+void computeDisplacement(const SkVector& scale, SkBitmap* dst,
                          const SkBitmap& displ, const SkIPoint& offset,
                          const SkBitmap& src,
                          const SkIRect& bounds) {
@@ -77,14 +71,13 @@ void computeDisplacement(Extractor ex, const SkVector& scale, SkBitmap* dst,
     const SkVector scaleForColor = SkVector::Make(scale.fX * Inv8bit, scale.fY * Inv8bit);
     const SkVector scaleAdj = SkVector::Make(SK_ScalarHalf - scale.fX * SK_ScalarHalf,
                                              SK_ScalarHalf - scale.fY * SK_ScalarHalf);
+    const SkUnPreMultiply::Scale* table = SkUnPreMultiply::GetScaleTable();
     SkPMColor* dstPtr = dst->getAddr32(0, 0);
     for (int y = bounds.top(); y < bounds.bottom(); ++y) {
         const SkPMColor* displPtr = displ.getAddr32(bounds.left() + offset.fX, y + offset.fY);
         for (int x = bounds.left(); x < bounds.right(); ++x, ++displPtr) {
-            SkPMColor c = unpremul_pm(*displPtr);
-
-            SkScalar displX = scaleForColor.fX * ex.getX(c) + scaleAdj.fX;
-            SkScalar displY = scaleForColor.fY * ex.getY(c) + scaleAdj.fY;
+            SkScalar displX = scaleForColor.fX * getValue<typeX>(*displPtr, table) + scaleAdj.fX;
+            SkScalar displY = scaleForColor.fY * getValue<typeY>(*displPtr, table) + scaleAdj.fY;
             // Truncate the displacement values
             const int srcX = x + SkScalarTruncToInt(displX);
             const int srcY = y + SkScalarTruncToInt(displY);
@@ -94,6 +87,64 @@ void computeDisplacement(Extractor ex, const SkVector& scale, SkBitmap* dst,
     }
 }
 
+template<SkDisplacementMapEffect::ChannelSelectorType typeX>
+void computeDisplacement(SkDisplacementMapEffect::ChannelSelectorType yChannelSelector,
+                         const SkVector& scale, SkBitmap* dst,
+                         const SkBitmap& displ, const SkIPoint& offset,
+                         const SkBitmap& src,
+                         const SkIRect& bounds) {
+    switch (yChannelSelector) {
+      case SkDisplacementMapEffect::kR_ChannelSelectorType:
+        computeDisplacement<typeX, SkDisplacementMapEffect::kR_ChannelSelectorType>(
+            scale, dst, displ, offset, src, bounds);
+        break;
+      case SkDisplacementMapEffect::kG_ChannelSelectorType:
+        computeDisplacement<typeX, SkDisplacementMapEffect::kG_ChannelSelectorType>(
+            scale, dst, displ, offset, src, bounds);
+        break;
+      case SkDisplacementMapEffect::kB_ChannelSelectorType:
+        computeDisplacement<typeX, SkDisplacementMapEffect::kB_ChannelSelectorType>(
+            scale, dst, displ, offset, src, bounds);
+        break;
+      case SkDisplacementMapEffect::kA_ChannelSelectorType:
+        computeDisplacement<typeX, SkDisplacementMapEffect::kA_ChannelSelectorType>(
+            scale, dst, displ, offset, src, bounds);
+        break;
+      case SkDisplacementMapEffect::kUnknown_ChannelSelectorType:
+      default:
+        SkDEBUGFAIL("Unknown Y channel selector");
+    }
+}
+
+void computeDisplacement(SkDisplacementMapEffect::ChannelSelectorType xChannelSelector,
+                         SkDisplacementMapEffect::ChannelSelectorType yChannelSelector,
+                         const SkVector& scale, SkBitmap* dst,
+                         const SkBitmap& displ, const SkIPoint& offset,
+                         const SkBitmap& src,
+                         const SkIRect& bounds) {
+    switch (xChannelSelector) {
+      case SkDisplacementMapEffect::kR_ChannelSelectorType:
+        computeDisplacement<SkDisplacementMapEffect::kR_ChannelSelectorType>(
+            yChannelSelector, scale, dst, displ, offset, src, bounds);
+        break;
+      case SkDisplacementMapEffect::kG_ChannelSelectorType:
+        computeDisplacement<SkDisplacementMapEffect::kG_ChannelSelectorType>(
+            yChannelSelector, scale, dst, displ, offset, src, bounds);
+        break;
+      case SkDisplacementMapEffect::kB_ChannelSelectorType:
+        computeDisplacement<SkDisplacementMapEffect::kB_ChannelSelectorType>(
+            yChannelSelector, scale, dst, displ, offset, src, bounds);
+        break;
+      case SkDisplacementMapEffect::kA_ChannelSelectorType:
+        computeDisplacement<SkDisplacementMapEffect::kA_ChannelSelectorType>(
+            yChannelSelector, scale, dst, displ, offset, src, bounds);
+        break;
+      case SkDisplacementMapEffect::kUnknown_ChannelSelectorType:
+      default:
+        SkDEBUGFAIL("Unknown X channel selector");
+    }
+}
+
 bool channel_selector_type_is_valid(SkDisplacementMapEffect::ChannelSelectorType cst) {
     switch (cst) {
     case SkDisplacementMapEffect::kUnknown_ChannelSelectorType:
@@ -347,7 +398,7 @@ sk_sp<SkSpecialImage> SkDisplacementMapEffect::onFilterImage(SkSpecialImage* sou
         return nullptr;
     }
 
-    computeDisplacement(Extractor(fXChannelSelector, fYChannelSelector), scale, &dst,
+    computeDisplacement(fXChannelSelector, fYChannelSelector, scale, &dst,
                         displBM, colorOffset - displOffset, colorBM, colorBounds);
 
     offset->fX = bounds.left();