gecko-dev/dom/base/ImageEncoder.h

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#ifndef ImageEncoder_h
#define ImageEncoder_h

#include "imgIEncoder.h"
#include "nsError.h"
#include "mozilla/dom/File.h"
#include "mozilla/dom/HTMLCanvasElementBinding.h"
#include "mozilla/UniquePtr.h"
#include "nsSize.h"

class nsICanvasRenderingContextInternal;

namespace mozilla {

namespace layers {
class Image;
}  // namespace layers

namespace dom {

class EncodeCompleteCallback;
class EncodingRunnable;
class OffscreenCanvasDisplayHelper;

class ImageEncoder {
 public:
  // Extracts data synchronously and gives you a stream containing the image
  // represented by aContext. aType may change to "image/png" if we had to fall
  // back to a PNG encoder. A return value of NS_OK implies successful data
  // extraction. If there are any unrecognized custom parse options in
  // aOptions, NS_ERROR_INVALID_ARG will be returned. When encountering this
  // error it is usual to call this function again without any options at all.
  static nsresult ExtractData(nsAString& aType, const nsAString& aOptions,
                              const nsIntSize aSize, bool aUsePlaceholder,
                              nsICanvasRenderingContextInternal* aContext,
                              OffscreenCanvasDisplayHelper* aOffscreenDisplay,
                              nsIInputStream** aStream);

  // Extracts data asynchronously. aType may change to "image/png" if we had to
  // fall back to a PNG encoder. aOptions are the options to be passed to the
  // encoder and aUsingCustomOptions specifies whether custom parse options were
  // used (i.e. by using -moz-parse-options). If there are any unrecognized
  // custom parse options, we fall back to the default values for the encoder
  // without any options at all. A return value of NS_OK only implies
  // successful dispatching of the extraction step to the encoding thread.
  // aEncodeCallback will be called on main thread when encoding process is
  // success.
  // Note: The callback has to set a valid parent for content for the generated
  // Blob object.
  static nsresult ExtractDataAsync(nsAString& aType, const nsAString& aOptions,
                                   bool aUsingCustomOptions,
                                   UniquePtr<uint8_t[]> aImageBuffer,
                                   int32_t aFormat, const nsIntSize aSize,
                                   bool aUsePlaceholder,
                                   EncodeCompleteCallback* aEncodeCallback);

  // Extract an Image asynchronously. Its function is same as ExtractDataAsync
  // except for the parameters. aImage is the uncompressed data. aEncodeCallback
  // will be called on main thread when encoding process is success.
  // Note: The callback has to set a valid parent for content for the generated
  // Blob object.
  static nsresult ExtractDataFromLayersImageAsync(
      nsAString& aType, const nsAString& aOptions, bool aUsingCustomOptions,
      layers::Image* aImage, bool aUsePlaceholder,
      EncodeCompleteCallback* aEncodeCallback);

  // Gives you a stream containing the image represented by aImageBuffer.
  // The format is given in aFormat, for example
  // imgIEncoder::INPUT_FORMAT_HOSTARGB.
  static nsresult GetInputStream(int32_t aWidth, int32_t aHeight,
                                 uint8_t* aImageBuffer, int32_t aFormat,
                                 imgIEncoder* aEncoder,
                                 const nsAString& aEncoderOptions,
                                 nsIInputStream** aStream);

 private:
  // When called asynchronously, aContext and aRenderer are null.
  static nsresult ExtractDataInternal(
      const nsAString& aType, const nsAString& aOptions, uint8_t* aImageBuffer,
      int32_t aFormat, const nsIntSize aSize, bool aUsePlaceholder,
      layers::Image* aImage, nsICanvasRenderingContextInternal* aContext,
      OffscreenCanvasDisplayHelper* aOffscreenDisplay, nsIInputStream** aStream,
      imgIEncoder* aEncoder);

  // Creates and returns an encoder instance of the type specified in aType.
  // aType may change to "image/png" if no instance of the original type could
  // be created and we had to fall back to a PNG encoder. A null return value
  // should be interpreted as NS_IMAGELIB_ERROR_NO_ENCODER and aType is
  // undefined in this case.
  static already_AddRefed<imgIEncoder> GetImageEncoder(nsAString& aType);

  friend class EncodingRunnable;
  friend class EncoderThreadPoolTerminator;
};

/**
 *  The callback interface of ExtractDataAsync and
 * ExtractDataFromLayersImageAsync. ReceiveBlobImpl() is called on main thread
 * when encoding is complete.
 */
class EncodeCompleteCallback {
 public:
  NS_INLINE_DECL_THREADSAFE_REFCOUNTING(EncodeCompleteCallback)

  MOZ_CAN_RUN_SCRIPT
  virtual nsresult ReceiveBlobImpl(already_AddRefed<BlobImpl> aBlobImpl) = 0;

  // CanBeDeletedOnAnyThread is pure virtual, so that whoever extends this class
  // needs to think how to handle cases like the owning DOM worker thread
  // shutting down.
  virtual bool CanBeDeletedOnAnyThread() = 0;

 protected:
  virtual ~EncodeCompleteCallback() = default;
};

}  // namespace dom
}  // namespace mozilla

#endif  // ImageEncoder_h