Plugs in the new thumbnailing algorithm to ThumbnailTabHelper.

chrome/browser/thumbnails/advanced_thumbnail_crop.cc

+// Copyright (c) 2013 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 "chrome/browser/thumbnails/advanced_thumbnail_crop.h"
+
+#include "base/metrics/histogram.h"
+#include "base/threading/sequenced_worker_pool.h"
+#include "chrome/browser/thumbnails/content_analysis.h"
+#include "chrome/browser/thumbnails/simple_thumbnail_crop.h"
+#include "content/public/browser/browser_thread.h"
+#include "third_party/skia/include/core/SkBitmap.h"
+#include "ui/gfx/scrollbar_size.h"
+#include "ui/gfx/size_conversions.h"
+#include "ui/gfx/skbitmap_operations.h"
+#include "ui/gfx/skia_util.h"
+
+namespace {

[mazda, 2013/05/23 19:13:57]

nit: add one empty line

[motek., 2013/05/27 16:54:54]

Done.

+static const char kThumbnailHistogramName[] = "Thumbnail.RetargetMS";
+static const char kFailureHistogramName[] = "Thumbnail.FailedRetargetMS";
+
+void CallbackInvocationAdapter(
+    const thumbnails::ThumbnailingAlgorithm::ConsumerCallback& callback,
+    scoped_refptr<thumbnails::ThumbnailingContext> context,
+    const SkBitmap& source_bitmap) {
+  callback.Run(*context, source_bitmap);
+}
+
+}

[mazda, 2013/05/23 19:13:57]

}  // namespace

[motek., 2013/05/27 16:54:54]

Done.

+
+namespace thumbnails {
+
+using content::BrowserThread;
+
+AdvancedThumbnailCrop::AdvancedThumbnailCrop(const gfx::Size& target_size)
+    : target_size_(target_size) {
+  DCHECK(!target_size.IsEmpty());
+}
+
+ClipResult AdvancedThumbnailCrop::GetCanvasCopyInfo(
+    const gfx::Size& source_size,
+    ui::ScaleFactor scale_factor,
+    gfx::Rect* clipping_rect,
+    gfx::Size* target_size) const {
+  DCHECK(!source_size.IsEmpty());
+  gfx::Size target_thumbnail_size =
+      SimpleThumbnailCrop::GetCopySizeForThumbnail(scale_factor, target_size_);
+
+  ClipResult clipping_method = thumbnails::CLIP_RESULT_NOT_CLIPPED;
+  *clipping_rect = GetClippingRect(
+      source_size, target_thumbnail_size, target_size, &clipping_method);
+  return clipping_method;
+}
+
+void AdvancedThumbnailCrop::ProcessBitmap(
+    scoped_refptr<ThumbnailingContext> context,
+    const ConsumerCallback& callback,
+    const SkBitmap& bitmap) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+  DCHECK(context);
+  if (bitmap.isNull() || bitmap.empty())
+    return;
+
+  float max_scale_factor =
+      ui::GetScaleFactorScale(ui::GetMaxScaleFactor());
+  gfx::Size target_thumbnail_size = gfx::ToFlooredSize(
+      gfx::ScaleSize(target_size_, max_scale_factor));

[mazda, 2013/05/23 19:13:57]

Could you share this logic of how the scale factor is chosen with
SimpleThumbnailCrop?

[motek., 2013/05/27 16:54:54]

I did it by applying some refactoring. Effectively, the entire stanza is shared.
I also attempted to clarify comments so that they apply in both contexts. 

+
+  SkBitmap source_bitmap = PrepareSourceBitmap(
+      bitmap, target_thumbnail_size, context);
+
+  // If the source is same (or smaller) than the target, just return it as
+  // the final result. Otherwise, send the shrinking task to the blocking
+  // thread pool.
+  if (source_bitmap.width() <= target_thumbnail_size.width() ||
+      source_bitmap.height() <= target_thumbnail_size.height()) {
+    context->score.boring_score =
+        SimpleThumbnailCrop::CalculateBoringScore(source_bitmap);
+    context->score.good_clipping =
+        (context->clip_result == CLIP_RESULT_WIDER_THAN_TALL ||
+         context->clip_result == CLIP_RESULT_TALLER_THAN_WIDE ||
+         context->clip_result == CLIP_RESULT_NOT_CLIPPED ||
+         context->clip_result == CLIP_RESULT_SOURCE_SAME_AS_TARGET);
+
+    callback.Run(*context, source_bitmap);
+    return;
+  }
+
+  if (!BrowserThread::GetBlockingPool()->PostWorkerTaskWithShutdownBehavior(
+          FROM_HERE,
+          base::Bind(&CreateRetargettedThumbnail,
+                     source_bitmap,
+                     target_thumbnail_size,
+                     context,
+                     callback),
+          base::SequencedWorkerPool::SKIP_ON_SHUTDOWN)) {
+    LOG(WARNING) << "PostSequencedWorkerTask failed. " <<
+        "The thumbnail for " << context->url << " will not be created.";

[mazda, 2013/05/23 19:13:57]

Move "<<" from the previous line and align it with the first "<<" on the
previous line.

LOG(WARNING) << "PostSequencedWorkerTask failed. "
             << "The thumbnail for " << context->url << " will not be created.";

[motek., 2013/05/27 16:54:54]

Done.

+  }
+}
+
+// static
+SkBitmap AdvancedThumbnailCrop::PrepareSourceBitmap(
+    const SkBitmap& received_bitmap,
+    const gfx::Size& thumbnail_size,
+    ThumbnailingContext* context) {
+
+  gfx::Size resize_target;
+  SkBitmap clipped_bitmap;
+  if (context->clip_result == CLIP_RESULT_UNPROCESSED) {
+    // This case will require extracting a fragment from the retrieved bitmap.
+    int scrollbar_size = gfx::scrollbar_size();
+    gfx::Size scrollbarless(
+        std::max(1, received_bitmap.width() - scrollbar_size),
+        std::max(1, received_bitmap.height() - scrollbar_size));
+
+    gfx::Rect clipping_rect = AdvancedThumbnailCrop::GetClippingRect(
+        scrollbarless,
+        thumbnail_size,
+        &resize_target,
+        &context->clip_result);
+
+    received_bitmap.extractSubset(&clipped_bitmap,
+                                  gfx::RectToSkIRect(clipping_rect));
+  } else {
+    // This means that the source bitmap has been requested and at least
+    // clipped. Upstream code in same cases seems opportunistic and it may
+    // not perform actual resizing if copying with resize is not supported.
+    // In this case we will resize to the orignally requested copy size.
+    resize_target = context->requested_copy_size;
+    clipped_bitmap = received_bitmap;
+  }
+
+  SkBitmap result_bitmap = SkBitmapOperations::DownsampleByTwoUntilSize(
+      clipped_bitmap, resize_target.width(), resize_target.height());
+#if !defined(USE_AURA)
+  // If the bitmap has not been indeed resized, it has to be copied. In that
+  // case resampler simply returns a reference to the original bitmap, sitting
+  // in PlatformCanvas. One does not simply assign these 'magic' bitmaps to
+  // SkBitmap. They cannot be refcounted.
+  //
+  // With Aura, this does not happen since PlatformCanvas is platform
+  // idependent.
+  if (clipped_bitmap.width() == result_bitmap.width() &&
+      clipped_bitmap.height() == result_bitmap.height()) {
+    clipped_bitmap.copyTo(&result_bitmap, SkBitmap::kARGB_8888_Config);
+  }
+#endif
+
+  return result_bitmap;
+}
+
+// static
+void AdvancedThumbnailCrop::CreateRetargettedThumbnail(
+    const SkBitmap& source_bitmap,
+    const gfx::Size& thumbnail_size,
+    scoped_refptr<ThumbnailingContext> context,
+    const ConsumerCallback& callback) {
+  base::TimeTicks begin_compute_thumbnail = base::TimeTicks::Now();
+  float kernel_sigma =
+      context->clip_result == CLIP_RESULT_SOURCE_SAME_AS_TARGET ? 5.0f : 2.5f;
+  SkBitmap thumbnail = thumbnailing_utils::CreateRetargettedThumbnailImage(
+      source_bitmap, thumbnail_size, kernel_sigma);
+  bool processing_failed = thumbnail.empty();
+  if (processing_failed) {
+    // Log and apply the method very much like in SimpleThumbnailCrop (except
+    // that some clipping and copying is not required).
+    LOG(WARNING) << "CreateRetargettedThumbnailImage failed. " <<
+        "The thumbnail for " << context->url <<
+        " will be created the old-fashioned way.";

[mazda, 2013/05/23 19:13:57]

LOG(WARNING) << "CreateRetargettedThumbnailImage failed. "
             << "The thumbnail for " << context->url
             << " will be created the old-fashioned way.";

[motek., 2013/05/27 16:54:54]

Done.

+    ClipResult clip_result;
+    gfx::Rect clipping_rect = SimpleThumbnailCrop::GetClippingRect(
+        gfx::Size(source_bitmap.width(), source_bitmap.height()),
+        thumbnail_size,
+        &clip_result);
+    source_bitmap.extractSubset(&thumbnail, gfx::RectToSkIRect(clipping_rect));
+    thumbnail = SkBitmapOperations::DownsampleByTwoUntilSize(
+        thumbnail, thumbnail_size.width(), thumbnail_size.height());
+  }
+
+  HISTOGRAM_TIMES(
+      processing_failed ? kFailureHistogramName : kThumbnailHistogramName,
+      base::TimeTicks::Now() - begin_compute_thumbnail);
+  context->score.boring_score =
+        SimpleThumbnailCrop::CalculateBoringScore(source_bitmap);
+  if (!processing_failed)
+    context->score.boring_score *= 1.1f;  // A bit of a boost for retargetted.

[mazda, 2013/05/23 19:13:57]

Please make a constant variable for 1.1f.

[motek., 2013/05/27 16:54:54]

Done.

+  context->score.good_clipping =
+      (context->clip_result == CLIP_RESULT_WIDER_THAN_TALL ||
+       context->clip_result == CLIP_RESULT_TALLER_THAN_WIDE ||
+       context->clip_result == CLIP_RESULT_NOT_CLIPPED ||
+       context->clip_result == CLIP_RESULT_SOURCE_SAME_AS_TARGET);
+  // Post the result (the bitmap) back to the callback.
+  BrowserThread::PostTask(
+      BrowserThread::UI,
+      FROM_HERE,
+      base::Bind(&CallbackInvocationAdapter, callback, context, thumbnail));
+}
+
+AdvancedThumbnailCrop::~AdvancedThumbnailCrop() {
+}
+
+//  static
+gfx::Rect AdvancedThumbnailCrop::GetClippingRect(
+    const gfx::Size& source_size,
+    const gfx::Size& thumbnail_size,
+    gfx::Size* target_size,
+    ClipResult* clip_result) {
+  // Compute and return the clipping rectagle of the source image and the
+  // size of the target bitmap which will be used for the further processing.
+  // This function in 'general case' is trivial (don't clip, halve the source)
+  // but it is needed for handling edge cases (source smaller than the target
+  // thumbnail size).
+  DCHECK(target_size);
+  DCHECK(clip_result);
+  gfx::Rect clipping_rect;
+  if (source_size.width() < thumbnail_size.width() ||
+      source_size.height() < thumbnail_size.height()) {
+    clipping_rect = gfx::Rect(thumbnail_size);
+    *target_size = thumbnail_size;
+    *clip_result = CLIP_RESULT_SOURCE_IS_SMALLER;
+  } else if (source_size.width() < thumbnail_size.width() * 4 ||
+             source_size.height() < thumbnail_size.height() * 4) {
+    clipping_rect = gfx::Rect(source_size);
+    *target_size = source_size;
+    *clip_result = CLIP_RESULT_SOURCE_SAME_AS_TARGET;
+  } else {
+    clipping_rect = gfx::Rect(source_size);
+    target_size->SetSize(source_size.width() / 2, source_size.height() / 2);
+    *clip_result = CLIP_RESULT_NOT_CLIPPED;
+  }
+
+  return clipping_rect;
+}
+
+

[mazda, 2013/05/23 19:13:57]

nit: delete two empty lines

[motek., 2013/05/27 16:54:54]

Done.

+
+}  // namespace thumbnails