allow imagefilter to manage CTM decomposition

tests/ImageFilterTest.cpp

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkBitmap.h"
 #include "SkBlurImageFilter.h"
 #include "SkCanvas.h"
@@ skipping 1688 matching lines @@
 
     test_xfermode_cropped_input(canvas, reporter);
 }
 
 DEF_GPUTEST_FOR_ALL_GL_CONTEXTS(ImageFilterBlurLargeImage_Gpu, reporter, ctxInfo) {
     auto surface(SkSurface::MakeRenderTarget(ctxInfo.fGrContext, SkBudgeted::kYes,
                                              SkImageInfo::MakeN32Premul(100, 100)));
     test_large_blur_input(reporter, surface->getCanvas());
 }
 #endif
+
+/*
+ *  Test that colorfilterimagefilter does not require its CTM to be decomposed when it has more
+ *  than just scale/translate, but that other filters do.
+ */
+DEF_TEST(ImageFilterDecomposeCTM, reporter) {
+    // just need a colorfilter to exercise the corresponding imagefilter
+    sk_sp<SkColorFilter> cf = SkColorFilter::MakeModeFilter(SK_ColorRED, SkXfermode::kSrcATop_Mode);
+    sk_sp<SkImageFilter> cfif = SkColorFilterImageFilter::Make(cf, nullptr);
+    sk_sp<SkImageFilter> blif = SkBlurImageFilter::Make(3, 3, nullptr);
+
+    struct {
+        sk_sp<SkImageFilter> fFilter;
+        bool                 fExpectCanHandle;
+    } recs[] = {
+        { cfif,                                     true  },
+        { SkColorFilterImageFilter::Make(cf, cfif), true  },
+        { SkMergeImageFilter::Make(cfif, cfif),     true  },
+        { blif,                                     false },
+        { SkMergeImageFilter::Make(cfif, blif),     false },
+        { SkColorFilterImageFilter::Make(cf, blif), false },
+    };
+    
+    for (const auto& rec : recs) {
+        const bool canHandle = rec.fFilter->canHandleAffine();
+        REPORTER_ASSERT(reporter, canHandle == rec.fExpectCanHandle);
+    }
+}