image_decoder_skia.cc

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// Copyright 2013 The Flutter 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 "flutter/lib/ui/painting/image_decoder_skia.h"
 
#include <algorithm>
 
#include "flutter/fml/logging.h"
#include "flutter/fml/make_copyable.h"
#include "flutter/lib/ui/painting/display_list_image_gpu.h"
#include "third_party/skia/include/core/SkBitmap.h"
#include "third_party/skia/include/core/SkImage.h"
#include "third_party/skia/include/gpu/ganesh/SkImageGanesh.h"
 
namespace flutter {
 
ImageDecoderSkia::ImageDecoderSkia(
    const TaskRunners& runners,
    std::shared_ptr<fml::ConcurrentTaskRunner> concurrent_task_runner,
    fml::WeakPtr<IOManager> io_manager)
    : ImageDecoder(runners,
                   std::move(concurrent_task_runner),
                   std::move(io_manager)) {}
 
ImageDecoderSkia::~ImageDecoderSkia() = default;
 
static sk_sp<SkImage> ResizeRasterImage(const sk_sp<SkImage>& image,
                                        const SkISize& resized_dimensions,
                                        const fml::tracing::TraceFlow& flow) {
  FML_DCHECK(!image->isTextureBacked());
 
  TRACE_EVENT0("flutter", __FUNCTION__);
  flow.Step(__FUNCTION__);
 
  if (resized_dimensions.isEmpty()) {
    FML_LOG(ERROR) << "Could not resize to empty dimensions.";
    return nullptr;
  }
 
  if (image->dimensions() == resized_dimensions) {
    return image->makeRasterImage();
  }
 
  const auto scaled_image_info =
      image->imageInfo().makeDimensions(resized_dimensions);
 
  SkBitmap scaled_bitmap;
  if (!scaled_bitmap.tryAllocPixels(scaled_image_info)) {
    FML_LOG(ERROR) << "Failed to allocate memory for bitmap of size "
                   << scaled_image_info.computeMinByteSize() << "B";
    return nullptr;
  }
 
  if (!image->scalePixels(
          scaled_bitmap.pixmap(),
          SkSamplingOptions(SkFilterMode::kLinear, SkMipmapMode::kNone),
          SkImage::kDisallow_CachingHint)) {
    FML_LOG(ERROR) << "Could not scale pixels";
    return nullptr;
  }
 
  // Marking this as immutable makes the MakeFromBitmap call share the pixels
  // instead of copying.
  scaled_bitmap.setImmutable();
 
  auto scaled_image = SkImages::RasterFromBitmap(scaled_bitmap);
  if (!scaled_image) {
    FML_LOG(ERROR) << "Could not create a scaled image from a scaled bitmap.";
    return nullptr;
  }
 
  return scaled_image;
}
 
static sk_sp<SkImage> ImageFromDecompressedData(
    ImageDescriptor* descriptor,
    uint32_t target_width,
    uint32_t target_height,
    const fml::tracing::TraceFlow& flow) {
  TRACE_EVENT0("flutter", __FUNCTION__);
  flow.Step(__FUNCTION__);
  auto image = SkImages::RasterFromData(
      descriptor->image_info(), descriptor->data(), descriptor->row_bytes());
 
  if (!image) {
    FML_LOG(ERROR) << "Could not create image from decompressed bytes.";
    return nullptr;
  }
 
  if (!target_width && !target_height) {
    // No resizing requested. Just rasterize the image.
    return image->makeRasterImage();
  }
 
  return ResizeRasterImage(image, SkISize::Make(target_width, target_height),
                           flow);
}
 
sk_sp<SkImage> ImageDecoderSkia::ImageFromCompressedData(
    ImageDescriptor* descriptor,
    uint32_t target_width,
    uint32_t target_height,
    const fml::tracing::TraceFlow& flow) {
  TRACE_EVENT0("flutter", __FUNCTION__);
  flow.Step(__FUNCTION__);
 
  if (!descriptor->should_resize(target_width, target_height)) {
    // No resizing requested. Just decode & rasterize the image.
    sk_sp<SkImage> image = descriptor->image();
    return image ? image->makeRasterImage() : nullptr;
  }
 
  const SkISize source_dimensions = descriptor->image_info().dimensions();
  const SkISize resized_dimensions = {static_cast<int32_t>(target_width),
                                      static_cast<int32_t>(target_height)};
 
  auto decode_dimensions = descriptor->get_scaled_dimensions(
      std::max(static_cast<float>(resized_dimensions.width()) /
                   source_dimensions.width(),
               static_cast<float>(resized_dimensions.height()) /
                   source_dimensions.height()));
 
  // If the codec supports efficient sub-pixel decoding, decoded at a resolution
  // close to the target resolution before resizing.
  if (decode_dimensions != source_dimensions) {
    auto scaled_image_info =
        descriptor->image_info().makeDimensions(decode_dimensions);
 
    SkBitmap scaled_bitmap;
    if (!scaled_bitmap.tryAllocPixels(scaled_image_info)) {
      FML_LOG(ERROR) << "Failed to allocate memory for bitmap of size "
                     << scaled_image_info.computeMinByteSize() << "B";
      return nullptr;
    }
 
    const auto& pixmap = scaled_bitmap.pixmap();
    if (descriptor->get_pixels(pixmap)) {
      // Marking this as immutable makes the MakeFromBitmap call share
      // the pixels instead of copying.
      scaled_bitmap.setImmutable();
 
      auto decoded_image = SkImages::RasterFromBitmap(scaled_bitmap);
      FML_DCHECK(decoded_image);
      if (!decoded_image) {
        FML_LOG(ERROR)
            << "Could not create a scaled image from a scaled bitmap.";
        return nullptr;
      }
      return ResizeRasterImage(decoded_image, resized_dimensions, flow);
    }
  }
 
  auto image = descriptor->image();
  if (!image) {
    return nullptr;
  }
 
  return ResizeRasterImage(image, resized_dimensions, flow);
}
 
static SkiaGPUObject<SkImage> UploadRasterImage(
    sk_sp<SkImage> image,
    const fml::WeakPtr<IOManager>& io_manager,
    const fml::tracing::TraceFlow& flow) {
  TRACE_EVENT0("flutter", __FUNCTION__);
  flow.Step(__FUNCTION__);
 
  // Should not already be a texture image because that is the entire point of
  // the this method.
  FML_DCHECK(!image->isTextureBacked());
 
  if (!io_manager->GetResourceContext() || !io_manager->GetSkiaUnrefQueue()) {
    FML_LOG(ERROR)
        << "Could not acquire context of release queue for texture upload.";
    return {};
  }
 
  SkPixmap pixmap;
  if (!image->peekPixels(&pixmap)) {
    FML_LOG(ERROR) << "Could not peek pixels of image for texture upload.";
    return {};
  }
 
  SkiaGPUObject<SkImage> result;
  io_manager->GetIsGpuDisabledSyncSwitch()->Execute(
      fml::SyncSwitch::Handlers()
          .SetIfTrue([&result, &pixmap, &image] {
            SkSafeRef(image.get());
            sk_sp<SkImage> texture_image = SkImages::RasterFromPixmap(
                pixmap,
                [](const void* pixels, SkImages::ReleaseContext context) {
                  SkSafeUnref(static_cast<SkImage*>(context));
                },
                image.get());
            result = {std::move(texture_image), nullptr};
          })
          .SetIfFalse([&result, context = io_manager->GetResourceContext(),
                       &pixmap, queue = io_manager->GetSkiaUnrefQueue()] {
            TRACE_EVENT0("flutter", "MakeCrossContextImageFromPixmap");
            sk_sp<SkImage> texture_image =
                SkImages::CrossContextTextureFromPixmap(
                    context.get(),  // context
                    pixmap,         // pixmap
                    true,           // buildMips,
                    true            // limitToMaxTextureSize
                );
            if (!texture_image) {
              FML_LOG(ERROR) << "Could not make x-context image.";
              result = {};
            } else {
              result = {std::move(texture_image), queue};
            }
          }));
 
  return result;
}
 
// |ImageDecoder|
void ImageDecoderSkia::Decode(fml::RefPtr<ImageDescriptor> descriptor_ref_ptr,
                              uint32_t target_width,
                              uint32_t target_height,
                              const ImageResult& callback) {
  TRACE_EVENT0("flutter", __FUNCTION__);
  fml::tracing::TraceFlow flow(__FUNCTION__);
 
  // ImageDescriptors have Dart peers that must be collected on the UI thread.
  // However, closures in MakeCopyable below capture the descriptor. The
  // captures of copyable closures may be collected on any of the thread
  // participating in task execution.
  //
  // To avoid this issue, we resort to manually reference counting the
  // descriptor. Since all task flows invoke the `result` callback, the raw
  // descriptor is retained in the beginning and released in the `result`
  // callback.
  //
  // `ImageDecoder::Decode` itself is invoked on the UI thread, so the
  // collection of the smart pointer from which we obtained the raw descriptor
  // is fine in this scope.
  auto raw_descriptor = descriptor_ref_ptr.get();
  raw_descriptor->AddRef();
 
  FML_DCHECK(callback);
  FML_DCHECK(runners_.GetUITaskRunner()->RunsTasksOnCurrentThread());
 
  // Always service the callback (and cleanup the descriptor) on the UI thread.
  auto result =
      [callback, raw_descriptor, ui_runner = runners_.GetUITaskRunner()](
          SkiaGPUObject<SkImage> image, fml::tracing::TraceFlow flow) {
        ui_runner->PostTask(fml::MakeCopyable(
            [callback, raw_descriptor, image = std::move(image),
             flow = std::move(flow)]() mutable {
              // We are going to terminate the trace flow here. Flows cannot
              // terminate without a base trace. Add one explicitly.
              TRACE_EVENT0("flutter", "ImageDecodeCallback");
              flow.End();
              callback(DlImageGPU::Make(std::move(image)), {});
              raw_descriptor->Release();
            }));
      };
 
  if (!raw_descriptor->data() || raw_descriptor->data()->size() == 0) {
    result({}, std::move(flow));
    return;
  }
 
  concurrent_task_runner_->PostTask(
      fml::MakeCopyable([raw_descriptor,                          //
                         io_manager = io_manager_,                //
                         io_runner = runners_.GetIOTaskRunner(),  //
                         result,                                  //
                         target_width = target_width,             //
                         target_height = target_height,           //
                         flow = std::move(flow)                   //
  ]() mutable {
        // Step 1: Decompress the image.
        // On Worker.
 
        auto decompressed = raw_descriptor->is_compressed()
                                ? ImageFromCompressedData(raw_descriptor,  //
                                                          target_width,    //
                                                          target_height,   //
                                                          flow)
                                : ImageFromDecompressedData(raw_descriptor,  //
                                                            target_width,    //
                                                            target_height,   //
                                                            flow);
 
        if (!decompressed) {
          FML_DLOG(ERROR) << "Could not decompress image.";
          result({}, std::move(flow));
          return;
        }
 
        // Step 2: Update the image to the GPU.
        // On IO Thread.
 
        io_runner->PostTask(fml::MakeCopyable([io_manager, decompressed, result,
                                               flow =
                                                   std::move(flow)]() mutable {
          if (!io_manager) {
            FML_DLOG(ERROR) << "Could not acquire IO manager.";
            result({}, std::move(flow));
            return;
          }
 
          // If the IO manager does not have a resource context, the caller
          // might not have set one or a software backend could be in use.
          // Either way, just return the image as-is.
          if (!io_manager->GetResourceContext()) {
            result({std::move(decompressed), io_manager->GetSkiaUnrefQueue()},
                   std::move(flow));
            return;
          }
 
          auto uploaded =
              UploadRasterImage(std::move(decompressed), io_manager, flow);
 
          if (!uploaded.skia_object()) {
            FML_DLOG(ERROR) << "Could not upload image to the GPU.";
            result({}, std::move(flow));
            return;
          }
 
          // Finally, all done.
          result(std::move(uploaded), std::move(flow));
        }));
      }));
}
 
}  // namespace flutter