[gfx] Add a utility to calculate visible margins of an image.

ui/gfx/image/image_util_unittest.cc

Index: ui/gfx/image/image_util_unittest.cc
diff --git a/ui/gfx/image/image_util_unittest.cc b/ui/gfx/image/image_util_unittest.cc
index cd9d74898f622e7b821567a3d511ba545ef50127..74c39e68fa4818ed0f9b572abfcae4896c6d01fd 100644
--- a/ui/gfx/image/image_util_unittest.cc
+++ b/ui/gfx/image/image_util_unittest.cc
@@ -9,6 +9,8 @@
 #include "base/memory/scoped_ptr.h"
 #include "testing/gtest/include/gtest/gtest.h"
 #include "third_party/skia/include/core/SkBitmap.h"
+#include "third_party/skia/include/core/SkRect.h"
+#include "ui/gfx/image/image_skia.h"
 #include "ui/gfx/image/image_unittest_util.h"
 
 TEST(ImageUtilTest, JPEGEncodeAndDecode) {
@@ -23,3 +25,79 @@ TEST(ImageUtilTest, JPEGEncodeAndDecode) {
   // JPEG is lossy, so simply check that the image decoded successfully.
   EXPECT_FALSE(decoded.IsEmpty());
 }
+
+TEST(ImageUtilTest, TestVisibleMargins) {
+  // Image with non-transparent piece should return margins at those
+  // columns.
+  SkBitmap bitmap1;
+  bitmap1.setConfig(SkBitmap::kARGB_8888_Config, 16, 16);
+  bitmap1.allocPixels();
+  bitmap1.eraseColor(SK_ColorTRANSPARENT);
+  bitmap1.eraseArea(SkIRect::MakeLTRB(3, 3, 14, 14), SK_ColorYELLOW);
+  gfx::ImageSkia img = gfx::ImageSkia::CreateFrom1xBitmap(bitmap1);
+  int x = 0;
+  int y = 0;
+  gfx::VisibleMargins(img, &x, &y);
+  EXPECT_EQ(3, x);
+  EXPECT_EQ(13, y);
+  EXPECT_EQ(16, img.width());
+
+  // Full-width-transparent image should return margins in the center
+  // of the image.
+  SkBitmap bitmap2;
+  bitmap2.setConfig(SkBitmap::kARGB_8888_Config, 16, 16);
+  bitmap2.allocPixels();
+  bitmap2.eraseColor(SK_ColorTRANSPARENT);
+  gfx::ImageSkia img_transparent = gfx::ImageSkia::CreateFrom1xBitmap(bitmap2);
+  x = 0;
+  y = 0;
+  gfx::VisibleMargins(img_transparent, &x, &y);
+  EXPECT_EQ(8, x);
+  EXPECT_EQ(9, y);
+  EXPECT_EQ(16, img_transparent.width());
+
+  // Image with non-transparent piece that is skewed to one side should
+  // return margins at those columns.
+  SkBitmap bitmap3;
+  bitmap3.setConfig(SkBitmap::kARGB_8888_Config, 16, 16);
+  bitmap3.allocPixels();
+  bitmap3.eraseColor(SK_ColorTRANSPARENT);
+  bitmap3.eraseArea(SkIRect::MakeLTRB(3, 3, 5, 5), SK_ColorYELLOW);
+  gfx::ImageSkia img3 = gfx::ImageSkia::CreateFrom1xBitmap(bitmap3);
+  x = 0;
+  y = 0;
+  gfx::VisibleMargins(img3, &x, &y);
+  EXPECT_EQ(3, x);
+  EXPECT_EQ(4, y);
+  EXPECT_EQ(16, img3.width());
+
+  // Image with non-transparent piece that is at one edge should
+  // return margins at those columns.
+  SkBitmap bitmap4;
+  bitmap4.setConfig(SkBitmap::kARGB_8888_Config, 16, 16);
+  bitmap4.allocPixels();
+  bitmap4.eraseColor(SK_ColorTRANSPARENT);
+  bitmap4.eraseArea(SkIRect::MakeLTRB(0, 3, 5, 5), SK_ColorYELLOW);
+  gfx::ImageSkia img4 = gfx::ImageSkia::CreateFrom1xBitmap(bitmap4);
+  x = 0;
+  y = 0;
+  gfx::VisibleMargins(img4, &x, &y);
+  EXPECT_EQ(0, x);
+  EXPECT_EQ(4, y);
+  EXPECT_EQ(16, img4.width());
+
+  // Image with non-transparent piece that is at trailing edge should
+  // return margins at those columns.
+  SkBitmap bitmap5;
+  bitmap5.setConfig(SkBitmap::kARGB_8888_Config, 16, 16);
+  bitmap5.allocPixels();
+  bitmap5.eraseColor(SK_ColorTRANSPARENT);
+  bitmap5.eraseArea(SkIRect::MakeLTRB(4, 3, 16, 16), SK_ColorYELLOW);
+  gfx::ImageSkia img5 = gfx::ImageSkia::CreateFrom1xBitmap(bitmap5);
+  x = 0;
+  y = 0;
+  gfx::VisibleMargins(img5, &x, &y);
+  EXPECT_EQ(4, x);
+  EXPECT_EQ(15, y);
+  EXPECT_EQ(16, img5.width());
+}