Add SkOverdrawColorFilter

Uses the value in the src alpha channel to choose how
to set the dst pixel.

This is a part of a multi-part change to detect and
display gpu overdraw on Android.

CQ_INCLUDE_TRYBOTS=master.client.skia.compile:Build-Ubuntu-GCC-x86_64-Debug-NoGPU-Trybot

BUG:32370375

GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=5113

Change-Id: I07040929d8a46bbadd499dccec75eebef0e11d11
Reviewed-on: https://skia-review.googlesource.com/5113
Commit-Queue: Matt Sarett <msarett@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>

1 files changed, 68 insertions, 0 deletions

diff --git a/gm/overdrawcolorfilter.cpp b/gm/overdrawcolorfilter.cpp
new file mode 100644
index 0000000000..2eba228045
--- /dev/null
+++ b/gm/overdrawcolorfilter.cpp
@@ -0,0 +1,68 @@
+/*
+ * Copyright 2016 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "gm.h"
+#include "SkCanvas.h"
+#include "SkOverdrawColorFilter.h"
+
+static inline void set_bitmap(SkBitmap* bitmap, uint8_t alpha) {
+    for (int y = 0; y < bitmap->height(); y++) {
+        for (int x = 0; x < bitmap->width(); x++) {
+            uint8_t* addr = bitmap->getAddr8(x, y);
+            *addr = alpha;
+        }
+    }
+
+    bitmap->notifyPixelsChanged();
+}
+
+class OverdrawColorFilter : public skiagm::GM {
+public:
+    OverdrawColorFilter() {}
+
+protected:
+    virtual SkString onShortName() override {
+        return SkString("overdrawcolorfilter");;
+    }
+
+    virtual SkISize onISize() override {
+        return SkISize::Make(200, 400);
+    }
+
+    void onDraw(SkCanvas* canvas) override {
+        static const SkPMColor colors[SkOverdrawColorFilter::kNumColors] = {
+                0x80800000, 0x80008000, 0x80000080, 0x80808000, 0x80008080, 0x80800080,
+        };
+
+        SkPaint paint;
+        sk_sp<SkColorFilter> colorFilter = SkOverdrawColorFilter::Make(colors);
+        paint.setColorFilter(colorFilter);
+
+        SkImageInfo info = SkImageInfo::MakeA8(100, 100);
+        SkBitmap bitmap;
+        bitmap.allocPixels(info);
+        set_bitmap(&bitmap, 0);
+        canvas->drawBitmap(bitmap, 0, 0, &paint);
+        set_bitmap(&bitmap, 1);
+        canvas->drawBitmap(bitmap, 0, 100, &paint);
+        set_bitmap(&bitmap, 2);
+        canvas->drawBitmap(bitmap, 0, 200, &paint);
+        set_bitmap(&bitmap, 3);
+        canvas->drawBitmap(bitmap, 0, 300, &paint);
+        set_bitmap(&bitmap, 4);
+        canvas->drawBitmap(bitmap, 100, 0, &paint);
+        set_bitmap(&bitmap, 5);
+        canvas->drawBitmap(bitmap, 100, 100, &paint);
+        set_bitmap(&bitmap, 6);
+        canvas->drawBitmap(bitmap, 100, 200, &paint);
+    }
+
+private:
+    typedef GM INHERITED;
+};
+
+DEF_GM(return new OverdrawColorFilter;)