short circuit high quality scales that are actually the identity

src/core/SkBitmapProcState.cpp

Index: src/core/SkBitmapProcState.cpp
diff --git a/src/core/SkBitmapProcState.cpp b/src/core/SkBitmapProcState.cpp
index d48679e8c993b0ddbb4e7a989b6edad8855307cc..9b708ca82795deb00a1a35bd3c9738b520136b96 100644
--- a/src/core/SkBitmapProcState.cpp
+++ b/src/core/SkBitmapProcState.cpp
@@ -167,6 +167,21 @@ bool SkBitmapProcState::possiblyScaleImage() {
         SkScalar invScaleX = fInvMatrix.getScaleX();
         SkScalar invScaleY = fInvMatrix.getScaleY();
 
+        if (SkScalarNearlyEqual(invScaleX,1.0f) &&
+            SkScalarNearlyEqual(invScaleY,1.0f)) {
+            // short-circuit identity scaling; the output is supposed to
+            // be the same as the input, so we might as well go fast.
+
+            // TODO -- consider short circuiting here if the scale is

[reed1, 2014/08/08 18:28:21]

remove the TODO

[humper, 2014/08/08 18:39:05]

Done.

+            // CLOSE to one.
+
+            // Set our filter level to low -- the only post-filtering this
+            // image might require is some interpolation if the translation
+            // is fractional.
+            fFilterLevel = SkPaint::kLow_FilterLevel;
+            return false;
+        }
+
         fScaledCacheID = SkScaledImageCache::FindAndLock(fOrigBitmap,
                                                          invScaleX, invScaleY,
                                                          &fScaledBitmap);
@@ -218,8 +233,10 @@ bool SkBitmapProcState::possiblyScaleImage() {
         fInvMatrix.setTranslate(fInvMatrix.getTranslateX() / fInvMatrix.getScaleX(),
                                 fInvMatrix.getTranslateY() / fInvMatrix.getScaleY());
 
-        // no need for any further filtering; we just did it!
-        fFilterLevel = SkPaint::kNone_FilterLevel;
+        // Set our filter level to low -- the only post-filtering this
+        // image might require is some interpolation if the translation
+        // is fractional.
+        fFilterLevel = SkPaint::kLow_FilterLevel;
         unlocker.release();
         return true;
     }
@@ -458,6 +475,12 @@ bool SkBitmapProcState::chooseProcs(const SkMatrix& inv, const SkPaint& paint) {
 
     trivialMatrix = (fInvMatrix.getType() & ~SkMatrix::kTranslate_Mask) == 0;
 
+    //

[reed1, 2014/08/08 18:28:21]

remove //

+
+    if (trivialMatrix && fFilterLevel > SkPaint::kMedium_FilterLevel) {

[reed1, 2014/08/08 18:28:21]

I *think* we can remove this check now, yes?

[humper, 2014/08/08 18:39:04]

Done.

+        fFilterLevel = SkPaint::kMedium_FilterLevel;
+    }
+
     if (SkPaint::kHigh_FilterLevel == fFilterLevel) {
         // If this is still set, that means we wanted HQ sampling
         // but couldn't do it as a preprocess.  Let's try to install