add backdrop option to SaveLayerRec

gm/imagefilters.cpp

Index: gm/imagefilters.cpp
diff --git a/gm/imagefilters.cpp b/gm/imagefilters.cpp
index 5f1ae849490dd8971a99ab656d7f4b8bca48c255..951a934d8210614daf9ad41262ca8e7cf0dda8bb 100644
--- a/gm/imagefilters.cpp
+++ b/gm/imagefilters.cpp
@@ -104,3 +104,77 @@ DEF_SIMPLE_GM(fast_slow_blurimagefilter, canvas, 620, 260) {
         canvas->translate(r.width() + 20, 0);
     }
 }
+
+///////////////////////////////////////////////////////////////////////////////////////////////////
+#include "Resources.h"
+#include "SkBlurImageFilter.h"
+#include "SkMatrixConvolutionImageFilter.h"
+#include "SkMorphologyImageFilter.h"
+#include "SkColorMatrixFilter.h"
+#include "SkColorFilterImageFilter.h"
+#include "SkRRect.h"
+
+static void draw_set(SkCanvas* canvas, SkImageFilter* filters[], int count) {
+    const SkRect r = SkRect::MakeXYWH(30, 30, 200, 200);
+    const SkScalar offset = 250;
+    SkScalar dx = 0, dy = 0;
+
+    for (int i = 0; i < count; ++i) {
+        canvas->save();
+        SkRRect rr = SkRRect::MakeRectXY(r.makeOffset(dx, dy), 20, 20);
+        canvas->clipRRect(rr, SkRegion::kIntersect_Op, true);
+        canvas->saveLayer({ &rr.getBounds(), nullptr, filters[i], 0 });
+        canvas->drawColor(0x40FFFFFF);
+        canvas->restore();
+        canvas->restore();
+
+        if (0 == dx) {
+            dx = offset;
+        } else {
+            dx = 0;
+            dy = offset;
+        }
+    }
+}
+
+DEF_SIMPLE_GM(savelayer_with_backdrop, canvas, 830, 550) {
+    SkColorMatrix cm;
+    cm.setSaturation(10);
+    SkAutoTUnref<SkColorFilter> cf(SkColorMatrixFilter::Create(cm));
+    const SkScalar kernel[] = { 4, 0, 4, 0, -15, 0, 4, 0, 4 };
+    SkImageFilter* filters[] = {
+        SkBlurImageFilter::Create(10, 10),
+        SkDilateImageFilter::Create(8, 8),
+        SkMatrixConvolutionImageFilter::Create({ 3, 3 }, kernel, 1, 0, { 0, 0 },
+                                           SkMatrixConvolutionImageFilter::kClampToBlack_TileMode,
+                                               true),
+        SkColorFilterImageFilter::Create(cf),
+    };
+
+    const struct {
+        SkScalar    fSx, fSy, fTx, fTy;
+    } xforms[] = {
+        { 1, 1, 0, 0 },
+        { 0.5f, 0.5f, 530, 0 },
+        { 0.25f, 0.25f, 530, 275 },
+        { 0.125f, 0.125f, 530, 420 },
+    };
+
+    SkPaint paint;
+    paint.setFilterQuality(kMedium_SkFilterQuality);
+    SkAutoTUnref<SkImage> image(GetResourceAsImage("mandrill_512.png"));
+
+    canvas->translate(20, 20);
+    for (const auto& xform : xforms) {
+        canvas->save();
+        canvas->translate(xform.fTx, xform.fTy);
+        canvas->scale(xform.fSx, xform.fSy);
+        canvas->drawImage(image, 0, 0, &paint);
+        draw_set(canvas, filters, SK_ARRAY_COUNT(filters));
+        canvas->restore();
+    }
+
+    for (auto& filter : filters) {
+        filter->unref();
+    }
+}