Factor out UnPreMultiplyPreservingByteOrder

BUG=
R=reed@google.com

Author: mtklein@google.com

Review URL: https://codereview.chromium.org/130303005

git-svn-id: http://skia.googlecode.com/svn/trunk@13103 2bbb7eff-a529-9590-31e7-b0007b416f81

4 files changed, 13 insertions, 19 deletions

diff --git a/dm/DMWriteTask.cpp b/dm/DMWriteTask.cpp
index 11a71faed6..faa20a2cc3 100644
--- a/dm/DMWriteTask.cpp
+++ b/dm/DMWriteTask.cpp
@@ -137,17 +137,11 @@ bool WriteTask::Expectations::check(const Task& task, SkBitmap bitmap) const {
         unpremul.setConfig(info);
         unpremul.allocPixels();
 
-        // Unpremultiply without changing native byte order.
         SkAutoLockPixels lockSrc(bitmap), lockDst(unpremul);
         const SkPMColor* src = (SkPMColor*)bitmap.getPixels();
         uint32_t* dst = (uint32_t*)unpremul.getPixels();
         for (size_t i = 0; i < bitmap.getSize()/4; i++) {
-            const U8CPU a = SkGetPackedA32(src[i]);
-            const SkUnPreMultiply::Scale s = SkUnPreMultiply::GetScale(a);
-            dst[i] = SkPackARGB32NoCheck(a,
-                                         SkUnPreMultiply::ApplyScale(s, SkGetPackedR32(src[i])),
-                                         SkUnPreMultiply::ApplyScale(s, SkGetPackedG32(src[i])),
-                                         SkUnPreMultiply::ApplyScale(s, SkGetPackedB32(src[i])));
+            dst[i] = SkUnPreMultiply::UnPreMultiplyPreservingByteOrder(src[i]);
         }
         bitmap.swap(unpremul);
     }
diff --git a/include/core/SkUnPreMultiply.h b/include/core/SkUnPreMultiply.h
index 4fa5d579e9..16181ce4e6 100644
--- a/include/core/SkUnPreMultiply.h
+++ b/include/core/SkUnPreMultiply.h
@@ -49,6 +49,8 @@ public:
 
     static SkColor PMColorToColor(SkPMColor c);
 
+    static uint32_t UnPreMultiplyPreservingByteOrder(SkPMColor c);
+
 private:
     static const uint32_t gTable[256];
 };
diff --git a/src/core/SkUnPreMultiply.cpp b/src/core/SkUnPreMultiply.cpp
index ad87f8af14..6245e96429 100644
--- a/src/core/SkUnPreMultiply.cpp
+++ b/src/core/SkUnPreMultiply.cpp
@@ -17,6 +17,15 @@ SkColor SkUnPreMultiply::PMColorToColor(SkPMColor c) {
                           ApplyScale(scale, SkGetPackedB32(c)));
 }
 
+uint32_t SkUnPreMultiply::UnPreMultiplyPreservingByteOrder(SkPMColor c) {
+    const U8CPU a = SkGetPackedA32(c);
+    const Scale scale = GetScale(a);
+    return SkPackARGB32NoCheck(a,
+                               ApplyScale(scale, SkGetPackedR32(c)),
+                               ApplyScale(scale, SkGetPackedG32(c)),
+                               ApplyScale(scale, SkGetPackedB32(c)));
+}
+
 const uint32_t SkUnPreMultiply::gTable[] = {
     0x00000000, 0xFF000000, 0x7F800000, 0x55000000, 0x3FC00000, 0x33000000, 0x2A800000, 0x246DB6DB,
     0x1FE00000, 0x1C555555, 0x19800000, 0x172E8BA3, 0x15400000, 0x139D89D9, 0x1236DB6E, 0x11000000,
diff --git a/src/ports/SkImageDecoder_CG.cpp b/src/ports/SkImageDecoder_CG.cpp
index 9b93f81112..beb6ed11e4 100644
--- a/src/ports/SkImageDecoder_CG.cpp
+++ b/src/ports/SkImageDecoder_CG.cpp
@@ -50,17 +50,6 @@ protected:
     virtual bool onDecode(SkStream* stream, SkBitmap* bm, Mode);
 };
 
-// Returns an unpremultiplied version of color. It will have the same ordering and size as an
-// SkPMColor, but the alpha will not be premultiplied.
-static SkPMColor unpremultiply_pmcolor(SkPMColor color) {
-    U8CPU a = SkGetPackedA32(color);
-    const SkUnPreMultiply::Scale scale = SkUnPreMultiply::GetScale(a);
-    return SkPackARGB32NoCheck(a,
-                               SkUnPreMultiply::ApplyScale(scale, SkGetPackedR32(color)),
-                               SkUnPreMultiply::ApplyScale(scale, SkGetPackedG32(color)),
-                               SkUnPreMultiply::ApplyScale(scale, SkGetPackedB32(color)));
-}
-
 #define BITMAP_INFO (kCGBitmapByteOrder32Big | kCGImageAlphaPremultipliedLast)
 
 bool SkImageDecoder_CG::onDecode(SkStream* stream, SkBitmap* bm, Mode mode) {
@@ -118,7 +107,7 @@ bool SkImageDecoder_CG::onDecode(SkStream* stream, SkBitmap* bm, Mode mode) {
         for (int i = 0; i < width; ++i) {
             for (int j = 0; j < height; ++j) {
                 uint32_t* addr = bm->getAddr32(i, j);
-                *addr = unpremultiply_pmcolor(*addr);
+                *addr = SkUnPreMultiply::UnPreMultiplyPreservingByteOrder(*addr);
             }
         }
         bm->setAlphaType(kUnpremul_SkAlphaType);