detect when we can filter bitmaps/images directly, w/o a tmp layer

src/core/SkDevice.cpp

 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkColorFilter.h"
 #include "SkDevice.h"
 #include "SkDraw.h"
@@ skipping 384 matching lines @@
                 m.postConcat(*matrix);
             }
             morphpath(&tmp, *iterPath, meas, m);
             this->drawPath(draw, tmp, iter.getPaint(), nullptr, true);
         }
     }
 }
 
 //////////////////////////////////////////////////////////////////////////////////////////
 
+bool SkBaseDevice::canCallFilterSprite(const SkMatrix* ctm, const SkPaint& paint) {
+    if (ctm && (ctm->getType() & ~SkMatrix::kTranslate_Mask)) {
+        return false;
+    }
+    const SkImageFilter* filter = paint.getImageFilter();
+    return filter && !this->canHandleImageFilter(filter);
+}
+
+void SkBaseDevice::filterSprite(const SkDraw& draw, const SkBitmap& bitmap, int x, int y,
+                                const SkPaint& paint) {
+    SkImageFilter* filter = paint.getImageFilter();
+    SkASSERT(filter && !this->canHandleImageFilter(filter));
+
+    SkImageFilter::DeviceProxy proxy(this);
+    SkBitmap dst;
+    SkIPoint offset = SkIPoint::Make(0, 0);
+    SkMatrix matrix = *draw.fMatrix;
+    matrix.postTranslate(SkIntToScalar(-x), SkIntToScalar(-y));
+    const SkIRect clipBounds = bitmap.bounds();
+    SkAutoTUnref<SkImageFilter::Cache> cache(this->getImageFilterCache());
+    SkImageFilter::Context ctx(matrix, clipBounds, cache.get(),
+                               SkImageFilter::kApprox_SizeConstraint);
+    if (filter->filterImage(&proxy, bitmap, ctx, &dst, &offset)) {
+        SkPaint tmpUnfiltered(paint);
+        tmpUnfiltered.setImageFilter(nullptr);
+        this->drawSprite(draw, dst, x + offset.x(), y + offset.y(), tmpUnfiltered);
+    }
+}
+
 uint32_t SkBaseDevice::filterTextFlags(const SkPaint& paint) const {
     uint32_t flags = paint.getFlags();
 
     if (!paint.isLCDRenderText() || !paint.isAntiAlias()) {
         return flags;
     }
 
     if (kUnknown_SkPixelGeometry == fSurfaceProps.pixelGeometry()
         || this->onShouldDisableLCD(paint)) {
 
         flags &= ~SkPaint::kLCDRenderText_Flag;
         flags |= SkPaint::kGenA8FromLCD_Flag;
     }
 
     return flags;
 }