Reland: Add ETC1 powered SSE encoder for tile texture compression

cc/resources/texture_compressor_etc1_unittest.cc

+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "cc/resources/texture_compressor.h"
+
+#include "cc/base/util.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace cc {
+namespace {
+
+const int kImageWidth = 256;
+const int kImageHeight = 256;
+const int kImageChannels = 4;
+const int kImageSizeInBytes = kImageWidth * kImageHeight * kImageChannels;
+
+TEST(TextureCompressorETC1Test, Compress256x256CreateETC1) {

[reveman, 2015/05/06 18:44:02]

This test is not ETC1 specific. If you think this is a useful test then please
move to a generic texture_compressor_unittest.cc file and run it with all types.

[radu.velea, 2015/05/07 11:21:41]

This might be useful for checking if all encoders are supported on a given
platform. I guess I can add something like this later on. Removing for now.

+  scoped_ptr<TextureCompressor> compressor =
+      TextureCompressor::Create(TextureCompressor::kFormatETC1);
+  EXPECT_NE(nullptr, compressor);
+}
+
+TEST(TextureCompressorETC1Test, Compress256x256RatioETC1) {

[reveman, 2015/05/06 18:44:02]

s/Compress256x256RatioETC1/Compress256x256Ratio/ as ETC1 is already in base test
name

+  scoped_ptr<TextureCompressor> compressor =
+      TextureCompressor::Create(TextureCompressor::kFormatETC1);
+  uint8_t src[kImageSizeInBytes];
+  uint8_t dst[kImageSizeInBytes];

[reveman, 2015/05/06 18:44:02]

How about we add TextureCompressor API that will return the minimum size needed
for a destination buffer and use that in a generic test instead of the
kImagePoison mechanism below?

[radu.velea, 2015/05/07 11:21:41]

That would be a good idea. I had a talk with christiank to return the "quality"
of the compressed image - ex: mean square error between the original image and
the texture resulting from decompressing the dst buffer; and use that in a unit
test as well. The metric would have to be a bit more complex if perceptual color
error functions are used, etc.

@christiank do you have any thoughts on this?

+  int compressed_size = 0;

[reveman, 2015/05/06 18:44:02]

nit: move this variable down to where it's first used

[radu.velea, 2015/05/07 11:21:41]

Done.

+  const unsigned int kImagePoison = 0xDEADBEEF;
+
+  /* Poison destination bytes */

[reveman, 2015/05/06 18:44:02]

nit: comment style

[radu.velea, 2015/05/07 11:21:41]

Done.

+  uint32_t* dst_32 = reinterpret_cast<uint32_t*>(dst);
+  for (int i = 0; i < kImageWidth * kImageHeight; i++) {
+    dst_32[i] = kImagePoison;
+  }
+
+  /* Generate test texture */

[reveman, 2015/05/06 18:44:02]

nit: comment style

[radu.velea, 2015/05/07 11:21:41]

Done.

+  for (int i = 0; i < kImageSizeInBytes; i++) {
+    src[i] = i % 256;
+  }
+
+  compressor->Compress(src, dst, kImageWidth, kImageHeight,
+                       (TextureCompressor::Quality)0);

[reveman, 2015/05/06 18:44:02]

Don't use c-style casts. I think we should use a valid quality setting here.

[radu.velea, 2015/05/07 11:21:41]

Done.

+  for (compressed_size = 0; compressed_size < kImageWidth * kImageHeight;
+       compressed_size++) {
+    if (dst_32[compressed_size] == kImagePoison) {
+      compressed_size =
+          compressed_size * 4; /* size in bytes of the compressed block */
+      break;
+    }
+  }
+
+  /* Check if compression ratio is 8:1 for RGBA or BGRA images, after discarding
+   * alpha channel */

[reveman, 2015/05/06 18:44:02]

nit: comment style

+  EXPECT_EQ(compressed_size * 8, kImageSizeInBytes);

[reveman, 2015/05/06 18:44:02]

expected value should be the first parameter

[radu.velea, 2015/05/07 11:21:41]

Done.

+}
+
+}  // namespace
+}  // namespace cc