images with offset bitmap don't share genid

BUG=skia:5096
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1813793002

Review URL: https://codereview.chromium.org/1813793002

2 files changed, 45 insertions, 1 deletions

diff --git a/src/image/SkImage_Raster.cpp b/src/image/SkImage_Raster.cpp
index 83daab7c44..892183a7c7 100644
--- a/src/image/SkImage_Raster.cpp
+++ b/src/image/SkImage_Raster.cpp
@@ -20,6 +20,14 @@
 #include "SkGrPriv.h"
 #endif
 
+// fixes https://bug.skia.org/5096
+static bool is_not_subset(const SkBitmap& bm) {
+    SkASSERT(bm.pixelRef());
+    SkISize dim = bm.pixelRef()->info().dimensions();
+    SkASSERT(dim != bm.dimensions() || bm.pixelRefOrigin().isZero());
+    return dim == bm.dimensions();
+}
+
 class SkImage_Raster : public SkImage_Base {
 public:
     static bool ValidArgs(const Info& info, size_t rowBytes, bool hasColorTable,
@@ -82,7 +90,9 @@ public:
     bool onAsLegacyBitmap(SkBitmap*, LegacyBitmapMode) const override;
 
     SkImage_Raster(const SkBitmap& bm)
-        : INHERITED(bm.width(), bm.height(), bm.getGenerationID())
+        : INHERITED(bm.width(), bm.height(),
+                    is_not_subset(bm) ? bm.getGenerationID()
+                                      : (uint32_t)kNeedNewImageUniqueID)
         , fBitmap(bm)
     {
         if (bm.pixelRef()->isPreLocked()) {
diff --git a/tests/image-bitmap.cpp b/tests/image-bitmap.cpp
new file mode 100644
index 0000000000..59ab3f72be
--- /dev/null
+++ b/tests/image-bitmap.cpp
@@ -0,0 +1,34 @@
+/*
+ * 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 "Test.h"
+
+#include "SkBitmap.h"
+#include "SkImage.h"
+
+// https://bug.skia.org/5096
+// Test that when we make an image from a subset of a bitmap, that it
+// has a diff (ID, dimensions) from an image made from the entire
+// bitmap or a different subset of the image.
+DEF_TEST(ImageBitmapIdentity, r) {
+    SkBitmap bm, a, b;
+    bm.allocN32Pixels(32, 64);
+    bm.eraseColor(SK_ColorBLACK);
+    bm.setImmutable();
+    (void)bm.extractSubset(&a, SkIRect::MakeXYWH(0, 0, 32, 32));
+    (void)bm.extractSubset(&b, SkIRect::MakeXYWH(0, 32, 32, 32));
+    REPORTER_ASSERT(r, a.getGenerationID() == b.getGenerationID());
+    auto img = SkImage::MakeFromBitmap(bm);
+    auto imgA = SkImage::MakeFromBitmap(a);
+    auto imgB = SkImage::MakeFromBitmap(b);
+    REPORTER_ASSERT(r, img->uniqueID() == bm.getGenerationID());
+    REPORTER_ASSERT(r, img->uniqueID() != imgA->uniqueID());
+    REPORTER_ASSERT(r, img->uniqueID() != imgB->uniqueID());
+    REPORTER_ASSERT(r, imgA->uniqueID() != imgB->uniqueID());
+    REPORTER_ASSERT(r, imgA->uniqueID() != a.getGenerationID());
+    REPORTER_ASSERT(r, imgB->uniqueID() != b.getGenerationID());
+}