lib/ui/painting/image_decoder.cc

// 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.h"

#include <algorithm>

#include "flutter/fml/make_copyable.h"
#include "third_party/skia/include/codec/SkCodec.h"

namespace flutter {

ImageDecoder::ImageDecoder(
    TaskRunners runners,
    std::shared_ptr<fml::ConcurrentTaskRunner> concurrent_task_runner,
    fml::WeakPtr<IOManager> io_manager)
    : runners_(std::move(runners)),
      concurrent_task_runner_(std::move(concurrent_task_runner)),
      io_manager_(std::move(io_manager)),
      weak_factory_(this) {
  FML_DCHECK(runners_.IsValid());
  FML_DCHECK(runners_.GetUITaskRunner()->RunsTasksOnCurrentThread())
      << "The image decoder must be created & collected on the UI thread.";
}

ImageDecoder::~ImageDecoder() = default;

static sk_sp<SkImage> ResizeRasterImage(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(), kLow_SkFilterQuality,
                          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 = SkImage::MakeFromBitmap(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(
    fml::RefPtr<ImageDescriptor> descriptor,
    uint32_t target_width,
    uint32_t target_height,
    const fml::tracing::TraceFlow& flow) {
  TRACE_EVENT0("flutter", __FUNCTION__);
  flow.Step(__FUNCTION__);
  auto image = SkImage::MakeRasterData(
      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(std::move(image),
                           SkISize::Make(target_width, target_height), flow);
}

sk_sp<SkImage> ImageFromCompressedData(fml::RefPtr<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<double>(resized_dimensions.width()) /
                   source_dimensions.width(),
               static_cast<double>(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 = SkImage::MakeFromBitmap(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(std::move(decoded_image), resized_dimensions,
                               flow);
    }
  }

  auto image = descriptor->image();
  if (!image) {
    return nullptr;
  }

  return ResizeRasterImage(std::move(image), resized_dimensions, flow);
}

static SkiaGPUObject<SkImage> UploadRasterImage(
    sk_sp<SkImage> image,
    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 = SkImage::MakeFromRaster(
                pixmap,
                [](const void* pixels, SkImage::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 = SkImage::MakeCrossContextFromPixmap(
                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;
}

void ImageDecoder::Decode(fml::RefPtr<ImageDescriptor> descriptor,
                          uint32_t target_width,
                          uint32_t target_height,
                          const ImageResult& callback) {
  TRACE_EVENT0("flutter", __FUNCTION__);
  fml::tracing::TraceFlow flow(__FUNCTION__);

  FML_DCHECK(callback);
  FML_DCHECK(runners_.GetUITaskRunner()->RunsTasksOnCurrentThread());

  // Always service the callback (and cleanup the descriptor) on the UI thread.
  auto result = [callback, descriptor, ui_runner = runners_.GetUITaskRunner()](
                    SkiaGPUObject<SkImage> image,
                    fml::tracing::TraceFlow flow) {
    ui_runner->PostTask(
        fml::MakeCopyable([callback, 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(std::move(image));
        }));
  };

  if (!descriptor->data() || descriptor->data()->size() == 0) {
    result({}, std::move(flow));
    return;
  }

  concurrent_task_runner_->PostTask(
      fml::MakeCopyable([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 =
            descriptor->is_compressed()
                ? ImageFromCompressedData(std::move(descriptor),  //
                                          target_width,           //
                                          target_height,          //
                                          flow)
                : ImageFromDecompressedData(std::move(descriptor),  //
                                            target_width,           //
                                            target_height,          //
                                            flow);

        if (!decompressed) {
          FML_LOG(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_LOG(ERROR) << "Could not acquire IO manager.";
            return result({}, std::move(flow));
          }

          // 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.get()) {
            FML_LOG(ERROR) << "Could not upload image to the GPU.";
            result({}, std::move(flow));
            return;
          }

          // Finally, all done.
          result(std::move(uploaded), std::move(flow));
        }));
      }));
}

fml::WeakPtr<ImageDecoder> ImageDecoder::GetWeakPtr() const {
  return weak_factory_.GetWeakPtr();
}

}  // namespace flutter