allow subpixel positioning w/ bitmap filtering

src/core/SkBitmapProcState.cpp

Index: src/core/SkBitmapProcState.cpp
diff --git a/src/core/SkBitmapProcState.cpp b/src/core/SkBitmapProcState.cpp
index 166b62c48cf40a2da9829b717db3fbcbadd1993b..ed5e6874795f636486f6a3f916317c2d3f9712ae 100644
--- a/src/core/SkBitmapProcState.cpp
+++ b/src/core/SkBitmapProcState.cpp
@@ -12,11 +12,17 @@
 #include "SkShader.h"   // for tilemodes
 #include "SkUtilsArm.h"
 #include "SkBitmapScaler.h"
+#include "SkMatrixUtils.h"
 #include "SkMipMap.h"
 #include "SkPixelRef.h"
 #include "SkScaledImageCache.h"
 #include "SkImageEncoder.h"
 
+static int paintfilter_to_subpixelbits(SkPaint::FilterLevel level) {
+    const int gBits[] = { 0, 4, 4, 4, };
+    return gBits[level];
+}
+
 #if !SK_ARM_NEON_IS_NONE
 // These are defined in src/opts/SkBitmapProcState_arm_neon.cpp
 extern const SkBitmapProcState::SampleProc16 gSkBitmapProcStateSample16_neon[];
@@ -374,14 +380,26 @@ SkBitmapProcState::~SkBitmapProcState() {
     SkDELETE(fBitmapFilter);
 }
 
+bool SkBitmapProcState::isInverseTrivial() const {
+    unsigned bits = paintfilter_to_subpixelbits((SkPaint::FilterLevel)fFilterLevel);
+    return SkTreatAsSprite(fInvMatrix, fBitmap->width(), fBitmap->height(), bits);
+}
+
 bool SkBitmapProcState::chooseProcs(const SkMatrix& inv, const SkPaint& paint) {
     SkASSERT(fOrigBitmap.width() && fOrigBitmap.height());
+    SkASSERT(NULL == fScaledCacheID);
 
-    fBitmap = NULL;
     fInvMatrix = inv;
     fFilterLevel = paint.getFilterLevel();
+    fBitmap = &fOrigBitmap;
 
-    SkASSERT(NULL == fScaledCacheID);
+    bool trivialMX = this->isInverseTrivial();
+    if (trivialMX) {
+        fFilterLevel = SkPaint::kNone_FilterLevel;
+    }
+
+    // Reset to null for possiblyScaleImage()
+    fBitmap = NULL;
 
     // possiblyScaleImage will look to see if it can rescale the image as a
     // preprocess; either by scaling up to the target size, or by selecting
@@ -406,11 +424,15 @@ bool SkBitmapProcState::chooseProcs(const SkMatrix& inv, const SkPaint& paint) {
         fFilterLevel = SkPaint::kLow_FilterLevel;
     }
 
-    bool trivialMatrix = (fInvMatrix.getType() & ~SkMatrix::kTranslate_Mask) == 0;
+    trivialMX = this->isInverseTrivial();
+    if (trivialMX) {
+        fFilterLevel = SkPaint::kNone_FilterLevel;
+    }
+
     bool clampClamp = SkShader::kClamp_TileMode == fTileModeX &&
                       SkShader::kClamp_TileMode == fTileModeY;
 
-    if (!(clampClamp || trivialMatrix)) {
+    if (!(clampClamp || trivialMX)) {
         fInvMatrix.postIDiv(fOrigBitmap.width(), fOrigBitmap.height());
     }
 
@@ -422,7 +444,8 @@ bool SkBitmapProcState::chooseProcs(const SkMatrix& inv, const SkPaint& paint) {
     // This code will only execute if the matrix has some scale component;
     // if it's already pure translate then we won't do this inversion.
 
-    if (matrix_only_scale_translate(fInvMatrix)) {
+//    if (matrix_only_scale_translate(fInvMatrix)) {
+    if (trivialMX) {
         SkMatrix forward;
         if (fInvMatrix.invert(&forward)) {
             if (clampClamp ? just_trans_clamp(forward, *fBitmap)
@@ -434,6 +457,10 @@ bool SkBitmapProcState::chooseProcs(const SkMatrix& inv, const SkPaint& paint) {
         }
     }
 
+    if (trivialMX && (fInvMatrix.getType() & ~SkMatrix::kTranslate_Mask)) {
+//        SkDebugf("sfsd\n");
+    }
+    
     fInvProc        = fInvMatrix.getMapXYProc();
     fInvType        = fInvMatrix.getType();
     fInvSx          = SkScalarToFixed(fInvMatrix.getScaleX());
@@ -448,11 +475,6 @@ bool SkBitmapProcState::chooseProcs(const SkMatrix& inv, const SkPaint& paint) {
     fSampleProc32 = NULL;
     fSampleProc16 = NULL;
 
-    // recompute the triviality of the matrix here because we may have
-    // changed it!
-
-    trivialMatrix = (fInvMatrix.getType() & ~SkMatrix::kTranslate_Mask) == 0;
-
     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
@@ -470,20 +492,10 @@ bool SkBitmapProcState::chooseProcs(const SkMatrix& inv, const SkPaint& paint) {
         }
     }
 
-    if (SkPaint::kLow_FilterLevel == fFilterLevel) {
-        // Only try bilerp if the matrix is "interesting" and
-        // the image has a suitable size.
-
-        if (fInvType <= SkMatrix::kTranslate_Mask ||
-                !valid_for_filtering(fBitmap->width() | fBitmap->height())) {
-            fFilterLevel = SkPaint::kNone_FilterLevel;
-        }
-    }
-
     // At this point, we know exactly what kind of sampling the per-scanline
     // shader will perform.
 
-    fMatrixProc = this->chooseMatrixProc(trivialMatrix);
+    fMatrixProc = this->chooseMatrixProc(trivialMX);
     // TODO(dominikg): SkASSERT(fMatrixProc) instead? chooseMatrixProc never returns NULL.
     if (NULL == fMatrixProc) {
         return false;