Add medium image quality to software predecode.

cc/tiles/software_image_decode_controller.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/tiles/software_image_decode_controller.h"
 
 #include <stdint.h>
 
+#include <algorithm>
 #include <functional>
 
 #include "base/format_macros.h"
 #include "base/macros.h"
 #include "base/memory/discardable_memory.h"
 #include "base/memory/ptr_util.h"
 #include "base/metrics/histogram_macros.h"
 #include "base/strings/stringprintf.h"
 #include "base/thread_task_runner_handle.h"
 #include "base/trace_event/memory_dump_manager.h"
@@ skipping 70 matching lines @@
 
  private:
   SoftwareImageDecodeController* controller_;
   SoftwareImageDecodeController::ImageKey image_key_;
   DrawImage image_;
   const ImageDecodeController::TracingInfo tracing_info_;
 
   DISALLOW_COPY_AND_ASSIGN(ImageDecodeTaskImpl);
 };
 
+// Most images are scaled from the source image's size to the target size.
+// But in the case of mipmaps, we are scaling from the mip level which is
+// larger than we need.
+// This function gets the scale of the mip level which will be used.
+SkSize GetMipMapScaleAdjustment(const gfx::Size& src_size,
+                                const gfx::Size& target_size) {
+  int src_height = src_size.height();
+  int src_width = src_size.width();
+  int target_height = target_size.height();
+  int target_width = target_size.width();

[vmpstr, 2016/05/02 19:58:26]

nit: you can early out if target_width or target_height are 0 (return (-1, -1),
and then NOTREACHED at the end). This works as well though.

[cblume, 2016/05/02 23:04:09]

I had tried this but still needed a final return, or else I would get an error
about control possibly reaching the end of the function. It does offer us an
early out though. But that is favoring the rare error case and introducing a
branch for all the good cases.

I'll go ahead and add it so you can take a look and see if you like it more.

+
+  int next_mip_height = src_height;
+  int next_mip_width = src_width;
+  for (int current_mip_level = 0;; current_mip_level++) {
+    int mip_height = next_mip_height;
+    int mip_width = next_mip_width;
+
+    next_mip_height = std::max(1, src_height / (1 << (current_mip_level + 1)));
+    next_mip_width = std::max(1, src_width / (1 << (current_mip_level + 1)));
+
+    // Check if an axis on the next mip level would be smaller than the target.
+    // If so, use the current mip level.
+    // This effectively always uses the larger image and always scales down.
+    if (next_mip_height < target_height || next_mip_width < target_width) {
+      SkScalar y_scale = static_cast<float>(mip_height) / src_height;
+      SkScalar x_scale = static_cast<float>(mip_width) / src_width;
+
+      return SkSize::Make(x_scale, y_scale);
+    }
+
+    if (mip_height == 1 && mip_width == 1) {
+      // We have reached the final mip level
+      if (target_height == 1 && target_width == 1) {

[vmpstr, 2016/05/02 19:58:26]

This is kind of meh... Do you still need this if you early out before?

[cblume, 2016/05/02 23:04:09]

This is for the final mip level case (say 1x1), not the 0 height/width error
case.

It is tricky. I previously was doing L123 "if (next_mip_height <
target_height..." and no check on this line. It would get to the final mip
level, see we haven't hit our target yet, and return an error. So it wasn't
handling 1x1.

My first attempt to handle the 1x1 case was to change L123 to <=. The problem
with that is say we have a 500x500 image that we want to present at 250x250.
Using the first mip level (not the base level) gives us exactly what we want.
But this would use the 500x500 image, instead of the 250x250 image.

So I arrived at this solution. I think it actually handles the 1x1 case pretty
well (or 1xM or Nx1). Only after we've scaled all the way down does it consider
this branch.

An alternative would be know in advance how many mip levels we need. Then we
don't need a special case for the final mip level. My original design had this.
We didn't like it because it relied on some bit manipulation math.

+        SkScalar y_scale = static_cast<float>(mip_height) / src_height;
+        SkScalar x_scale = static_cast<float>(mip_width) / src_width;
+
+        return SkSize::Make(x_scale, y_scale);
+      }
+
+      break;
+    }
+  }
+
+  return SkSize::Make(-1.f, -1.f);
+}
+
 SkSize GetScaleAdjustment(const ImageDecodeControllerKey& key) {
   // If the requested filter quality did not require scale, then the adjustment
   // is identity.
-  if (key.can_use_original_decode())
+  if (key.can_use_original_decode()) {
     return SkSize::Make(1.f, 1.f);
-
-  float x_scale =
-      key.target_size().width() / static_cast<float>(key.src_rect().width());
-  float y_scale =
-      key.target_size().height() / static_cast<float>(key.src_rect().height());
-  return SkSize::Make(x_scale, y_scale);
+  } else if (key.filter_quality() == kMedium_SkFilterQuality) {
+    return GetMipMapScaleAdjustment(key.src_rect().size(), key.target_size());
+  } else {
+    float x_scale =
+        key.target_size().width() / static_cast<float>(key.src_rect().width());
+    float y_scale = key.target_size().height() /
+                    static_cast<float>(key.src_rect().height());
+    return SkSize::Make(x_scale, y_scale);
+  }
 }
 
 SkFilterQuality GetDecodedFilterQuality(const ImageDecodeControllerKey& key) {
   return std::min(key.filter_quality(), kLow_SkFilterQuality);
 }
 
 SkImageInfo CreateImageInfo(size_t width,
                             size_t height,
                             ResourceFormat format) {
   return SkImageInfo::Make(width, height,
@@ skipping 61 matching lines @@
                "SoftwareImageDecodeController::GetTaskForImageAndRef", "key",
                key.ToString());
 
   // If the target size is empty, we can skip this image during draw (and thus
   // we don't need to decode it or ref it).
   if (key.target_size().IsEmpty()) {
     *task = nullptr;
     return false;
   }
 
-  // If we're not going to do a scale, we will just create a task to preroll the
-  // image the first time we see it. This doesn't need to account for memory.
-  // TODO(vmpstr): We can also lock the original sized image, in which case it
-  // does require memory bookkeeping.
-  if (!CanHandleImage(key)) {
-    base::AutoLock lock(lock_);
-    if (prerolled_images_.count(key.image_id()) == 0) {
-      scoped_refptr<TileTask>& existing_task = pending_image_tasks_[key];
-      if (!existing_task) {
-        existing_task = make_scoped_refptr(
-            new ImageDecodeTaskImpl(this, key, image, tracing_info));
-      }
-      *task = existing_task;
-    } else {
-      *task = nullptr;
-    }
-    return false;
-  }
-
   base::AutoLock lock(lock_);
 
   // If we already have the image in cache, then we can return it.
   auto decoded_it = decoded_images_.Get(key);
   bool new_image_fits_in_memory =
       locked_images_budget_.AvailableMemoryBytes() >= key.locked_bytes();
   if (decoded_it != decoded_images_.end()) {
     bool image_was_locked = decoded_it->second->is_locked();
     if (image_was_locked ||
         (new_image_fits_in_memory && decoded_it->second->Lock())) {
@@ skipping 62 matching lines @@
 }
 
 void SoftwareImageDecodeController::UnrefImage(const DrawImage& image) {
   // When we unref the image, there are several situations we need to consider:
   // 1. The ref did not reach 0, which means we have to keep the image locked.
   // 2. The ref reached 0, we should unlock it.
   //   2a. The image isn't in the locked cache because we didn't get to decode
   //       it yet (or failed to decode it).
   //   2b. Unlock the image but keep it in list.
   const ImageKey& key = ImageKey::FromDrawImage(image);
-  DCHECK(CanHandleImage(key)) << key.ToString();
   TRACE_EVENT1("disabled-by-default-cc.debug",
                "SoftwareImageDecodeController::UnrefImage", "key",
                key.ToString());
 
   base::AutoLock lock(lock_);
   auto ref_count_it = decoded_images_ref_counts_.find(key);
   DCHECK(ref_count_it != decoded_images_ref_counts_.end());
 
   --ref_count_it->second;
   if (ref_count_it->second == 0) {
@@ skipping 10 matching lines @@
     DCHECK(decoded_image_it->second->is_locked());
     decoded_image_it->second->Unlock();
   }
   SanityCheckState(__LINE__, true);
 }
 
 void SoftwareImageDecodeController::DecodeImage(const ImageKey& key,
                                                 const DrawImage& image) {
   TRACE_EVENT1("cc", "SoftwareImageDecodeController::DecodeImage", "key",
                key.ToString());
-  if (!CanHandleImage(key)) {
-    image.image()->preroll();
-
-    base::AutoLock lock(lock_);
-    prerolled_images_.insert(key.image_id());
-    // Erase the pending task from the queue, since the task won't be doing
-    // anything useful after this function terminates. Since we don't preroll
-    // images twice, this is actually not necessary but it behaves similar to
-    // the other code path: when this function finishes, the task isn't in the
-    // pending_image_tasks_ list.
-    pending_image_tasks_.erase(key);
-    return;
-  }
-
   base::AutoLock lock(lock_);
   AutoRemoveKeyFromTaskMap remove_key_from_task_map(&pending_image_tasks_, key);
 
   // We could have finished all of the raster tasks (cancelled) while the task
   // was just starting to run. Since this task already started running, it
   // wasn't cancelled. So, if the ref count for the image is 0 then we can just
   // abort.
   if (decoded_images_ref_counts_.find(key) ==
       decoded_images_ref_counts_.end()) {
     return;
@@ skipping 36 matching lines @@
   if (decoded_images_ref_counts_.find(key) ==
       decoded_images_ref_counts_.end()) {
     decoded_image->Unlock();
   }
 
   decoded_images_.Put(key, std::move(decoded_image));
   SanityCheckState(__LINE__, true);
 }
 
 std::unique_ptr<SoftwareImageDecodeController::DecodedImage>
+SoftwareImageDecodeController::GetMediumQualityImageDecode(
+    const ImageKey& key,
+    sk_sp<const SkImage> image) {
+  SkSize mipmap_scale =
+      GetMipMapScaleAdjustment(key.src_rect().size(), key.target_size());
+  DCHECK(mipmap_scale.width() > 0.f && mipmap_scale.height() > 0.f);
+
+  if (mipmap_scale.width() == 1.f && mipmap_scale.height() == 1.f) {
+    return GetOriginalImageDecode(key, std::move(image));
+  } else {
+    DrawImage mip_image(
+        image, gfx::RectToSkIRect(key.src_rect()), kMedium_SkFilterQuality,
+        SkMatrix::MakeScale(mipmap_scale.width(), mipmap_scale.height()));
+    auto mip_key = ImageKey::FromDrawImage(mip_image);

[vmpstr, 2016/05/02 19:58:26]

I'm a bit confused: wouldn't the passed key already have the right
target_width/height?

[cblume, 2016/05/02 23:04:09]

Good catch. After our change to ::FromDrawImage, this always already had the
right scale. This is about to get CLEAN yo!

+    return GetScaledImageDecode(mip_key, std::move(image));
+  }
+}
+
+std::unique_ptr<SoftwareImageDecodeController::DecodedImage>
 SoftwareImageDecodeController::DecodeImageInternal(
     const ImageKey& key,
     const DrawImage& draw_image) {
   TRACE_EVENT1("disabled-by-default-cc.debug",
                "SoftwareImageDecodeController::DecodeImageInternal", "key",
                key.ToString());
   sk_sp<const SkImage> image = draw_image.image();
   if (!image)
     return nullptr;
 
   switch (key.filter_quality()) {
     case kNone_SkFilterQuality:
     case kLow_SkFilterQuality:
       return GetOriginalImageDecode(key, std::move(image));
     case kMedium_SkFilterQuality:
-      NOTIMPLEMENTED();
-      return nullptr;
+      return GetMediumQualityImageDecode(key, std::move(image));
     case kHigh_SkFilterQuality:
       return GetScaledImageDecode(key, std::move(image));
     default:
       NOTREACHED();
       return nullptr;
   }
 }
 
 DecodedDrawImage SoftwareImageDecodeController::GetDecodedImageForDraw(
     const DrawImage& draw_image) {
   ImageKey key = ImageKey::FromDrawImage(draw_image);
   TRACE_EVENT1("disabled-by-default-cc.debug",
                "SoftwareImageDecodeController::GetDecodedImageForDraw", "key",
                key.ToString());
   // If the target size is empty, we can skip this image draw.
   if (key.target_size().IsEmpty())
     return DecodedDrawImage(nullptr, kNone_SkFilterQuality);
 
-  if (!CanHandleImage(key))
-    return DecodedDrawImage(draw_image.image(), draw_image.filter_quality());
-
   return GetDecodedImageForDrawInternal(key, draw_image);
 }
 
 DecodedDrawImage SoftwareImageDecodeController::GetDecodedImageForDrawInternal(
     const ImageKey& key,
     const DrawImage& draw_image) {
   TRACE_EVENT1("disabled-by-default-cc.debug",
                "SoftwareImageDecodeController::GetDecodedImageForDrawInternal",
                "key", key.ToString());
   base::AutoLock lock(lock_);
@@ skipping 157 matching lines @@
   {
     TRACE_EVENT0(
         "disabled-by-default-cc.debug",
         "SoftwareImageDecodeController::ScaleImage - allocate scaled pixels");
     scaled_pixels = base::DiscardableMemoryAllocator::GetInstance()
                         ->AllocateLockedDiscardableMemory(
                             scaled_info.minRowBytes() * scaled_info.height());
   }
   SkPixmap scaled_pixmap(scaled_info, scaled_pixels->data(),
                          scaled_info.minRowBytes());
-  // TODO(vmpstr): Start handling more than just high filter quality.
-  DCHECK_EQ(kHigh_SkFilterQuality, key.filter_quality());
+  DCHECK(key.filter_quality() == kHigh_SkFilterQuality ||
+         key.filter_quality() == kMedium_SkFilterQuality);
   {
     TRACE_EVENT0("disabled-by-default-cc.debug",
                  "SoftwareImageDecodeController::ScaleImage - scale pixels");
     bool result =
         decoded_pixmap.scalePixels(scaled_pixmap, key.filter_quality());
     DCHECK(result) << key.ToString();
   }
 
   // Release the original sized decode. Any other intermediate result to release
   // would be the subrect memory. However, that's in a scoped_ptr and will be
   // deleted automatically when we return.
   DrawWithImageFinished(original_size_draw_image, decoded_draw_image);
 
   return base::WrapUnique(
       new DecodedImage(scaled_info, std::move(scaled_pixels),
                        SkSize::Make(-key.src_rect().x(), -key.src_rect().y()),
                        next_tracing_id_.GetNext()));
 }
 
 void SoftwareImageDecodeController::DrawWithImageFinished(
     const DrawImage& image,
     const DecodedDrawImage& decoded_image) {
   TRACE_EVENT1("disabled-by-default-cc.debug",
                "SoftwareImageDecodeController::DrawWithImageFinished", "key",
                ImageKey::FromDrawImage(image).ToString());
   ImageKey key = ImageKey::FromDrawImage(image);
-  if (!decoded_image.image() || !CanHandleImage(key))
+  if (!decoded_image.image())
     return;
 
   if (decoded_image.is_at_raster_decode())
     UnrefAtRasterImage(key);
   else
     UnrefImage(image);
   SanityCheckState(__LINE__, false);
 }
 
 void SoftwareImageDecodeController::RefAtRasterImage(const ImageKey& key) {
@@ skipping 46 matching lines @@
       DCHECK(decoded_images_ref_counts_.find(key) ==
              decoded_images_ref_counts_.end());
       at_raster_image_it->second->Unlock();
       decoded_images_.Erase(image_it);
       decoded_images_.Put(key, std::move(at_raster_image_it->second));
     }
     at_raster_decoded_images_.Erase(at_raster_image_it);
   }
 }
 
-bool SoftwareImageDecodeController::CanHandleImage(const ImageKey& key) {
-  // TODO(vmpstr): Start handling medium filter quality as well.
-  return key.filter_quality() != kMedium_SkFilterQuality;
-}
-
 void SoftwareImageDecodeController::ReduceCacheUsage() {
   TRACE_EVENT0("cc", "SoftwareImageDecodeController::ReduceCacheUsage");
   base::AutoLock lock(lock_);
   size_t num_to_remove = (decoded_images_.size() > kMaxItemsInCache)
                              ? (decoded_images_.size() - kMaxItemsInCache)
                              : 0;
   for (auto it = decoded_images_.rbegin();
        num_to_remove != 0 && it != decoded_images_.rend();) {
     if (it->second->is_locked()) {
       ++it;
@@ skipping 128 matching lines @@
     }
   }
 
   bool can_use_original_decode =
       quality == kLow_SkFilterQuality || quality == kNone_SkFilterQuality;
 
   // If we're going to use the original decode, then the target size should be
   // the full image size, since that will allow for proper memory accounting.
   // Note we skip the decode if the target size is empty altogether, so don't
   // update the target size in that case.
   if (can_use_original_decode && !target_size.IsEmpty())

[vmpstr, 2016/05/02 19:58:26]

Should the below condition also check if target_size is empty?

[cblume, 2016/05/02 23:04:09]

Done.

     target_size = gfx::Size(image.image()->width(), image.image()->height());
 
+  if (quality == kMedium_SkFilterQuality) {
+    SkSize mip_target_size =
+        GetMipMapScaleAdjustment(src_rect.size(), target_size);
+    target_size.set_width(src_rect.width() * mip_target_size.width());
+    target_size.set_height(src_rect.height() * mip_target_size.height());
+  }
+
   return ImageDecodeControllerKey(image.image()->uniqueID(), src_rect,
                                   target_size, quality,
                                   can_use_original_decode);
 }
 
 ImageDecodeControllerKey::ImageDecodeControllerKey(
     uint32_t image_id,
     const gfx::Rect& src_rect,
     const gfx::Size& target_size,
     SkFilterQuality filter_quality,
@@ skipping 92 matching lines @@
 void SoftwareImageDecodeController::MemoryBudget::ResetUsage() {
   current_usage_bytes_ = 0;
 }
 
 size_t SoftwareImageDecodeController::MemoryBudget::GetCurrentUsageSafe()
     const {
   return current_usage_bytes_.ValueOrDie();
 }
 
 }  // namespace cc