arithmetic mode with Sk4f

src/effects/SkArithmeticMode.cpp

Index: src/effects/SkArithmeticMode.cpp
diff --git a/src/effects/SkArithmeticMode.cpp b/src/effects/SkArithmeticMode.cpp
index fbe6358ae4ece2550e28d09f76843da41f87dbca..e926f1bc9ad860d98999f732914cf0be03be2225 100644
--- a/src/effects/SkArithmeticMode.cpp
+++ b/src/effects/SkArithmeticMode.cpp
@@ -7,10 +7,11 @@
 
 #include "SkArithmeticMode.h"
 #include "SkColorPriv.h"
+#include "SkNx.h"
 #include "SkReadBuffer.h"
-#include "SkWriteBuffer.h"
 #include "SkString.h"
 #include "SkUnPreMultiply.h"
+#include "SkWriteBuffer.h"
 #if SK_SUPPORT_GPU
 #include "SkArithmeticMode_gpu.h"
 #endif
@@ -63,64 +64,37 @@ sk_sp<SkFlattenable> SkArithmeticMode_scalar::CreateProc(SkReadBuffer& buffer) {
     return SkArithmeticMode::Make(k1, k2, k3, k4, enforcePMColor);
 }
 
-static int pinToByte(int value) {
-    if (value < 0) {
-        value = 0;
-    } else if (value > 255) {
-        value = 255;
-    }
-    return value;
-}
+void SkArithmeticMode_scalar::xfer32(SkPMColor dst[], const SkPMColor src[],
+                                 int count, const SkAlpha aaCoverage[]) const {
+    const Sk4f k1 = fK[0] * (1/255.0f),
+               k2 = fK[1],
+               k3 = fK[2],
+               k4 = fK[3] * 255.0f + 0.5f;
+
+    auto pin = [](float min, const Sk4f& val, float max) {
+        return Sk4f::Max(min, Sk4f::Min(val, max));
+    };
+
+    for (int i = 0; i < count; i++) {
+        if (aaCoverage && aaCoverage[i] == 0) {
+            continue;
+        }
 
-static int arith(SkScalar k1, SkScalar k2, SkScalar k3, SkScalar k4,
-                 int src, int dst) {
-    SkScalar result = SkScalarMul(k1, src * dst) +
-                      SkScalarMul(k2, src) +
-                      SkScalarMul(k3, dst) +
-                      k4;
-    int res = SkScalarRoundToInt(result);
-    return pinToByte(res);
-}
+        Sk4f s = SkNx_cast<float>(Sk4b::Load(src+i)),
+             d = SkNx_cast<float>(Sk4b::Load(dst+i)),
+             r = pin(0, k1*s*d + k2*s + k3*d + k4, 255);
 
-static int blend(int src, int dst, int scale) {
-    return dst + ((src - dst) * scale >> 8);
-}
+        if (fEnforcePMColor) {
+            Sk4f a = SkNx_shuffle<3,3,3,3>(r);
+            r = Sk4f::Min(a, r);
+        }
 
-void SkArithmeticMode_scalar::xfer32(SkPMColor dst[], const SkPMColor src[],
-                                 int count, const SkAlpha aaCoverage[]) const {
-    SkScalar k1 = fK[0] / 255;
-    SkScalar k2 = fK[1];
-    SkScalar k3 = fK[2];
-    SkScalar k4 = fK[3] * 255;
-
-    for (int i = 0; i < count; ++i) {
-        if ((nullptr == aaCoverage) || aaCoverage[i]) {
-            SkPMColor sc = src[i];
-            SkPMColor dc = dst[i];
-
-            int a, r, g, b;
-
-            a = arith(k1, k2, k3, k4, SkGetPackedA32(sc), SkGetPackedA32(dc));
-            r = arith(k1, k2, k3, k4, SkGetPackedR32(sc), SkGetPackedR32(dc));
-            g = arith(k1, k2, k3, k4, SkGetPackedG32(sc), SkGetPackedG32(dc));
-            b = arith(k1, k2, k3, k4, SkGetPackedB32(sc), SkGetPackedB32(dc));
-            if (fEnforcePMColor) {
-                r = SkMin32(r, a);
-                g = SkMin32(g, a);
-                b = SkMin32(b, a);
-            }
-
-            // apply antialias coverage if necessary
-            if (aaCoverage && 0xFF != aaCoverage[i]) {
-                int scale = aaCoverage[i] + (aaCoverage[i] >> 7);
-                a = blend(a, SkGetPackedA32(sc), scale);
-                r = blend(r, SkGetPackedR32(sc), scale);
-                g = blend(g, SkGetPackedG32(sc), scale);
-                b = blend(b, SkGetPackedB32(sc), scale);
-            }
-
-            dst[i] = fEnforcePMColor ? SkPackARGB32(a, r, g, b) : SkPackARGB32NoCheck(a, r, g, b);
+        if (aaCoverage && aaCoverage[i] != 255) {
+            Sk4f c = aaCoverage[i] * (1/255.0f);
+            r = d + (r-d)*c;
         }
+
+        SkNx_cast<uint8_t>(r).store(dst+i);
     }
 }