src/cobalt/renderer/rasterizer/skia/image.h

// Copyright 2014 The Cobalt Authors. All Rights Reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#ifndef COBALT_RENDERER_RASTERIZER_SKIA_IMAGE_H_
#define COBALT_RENDERER_RASTERIZER_SKIA_IMAGE_H_

#include "cobalt/base/type_id.h"
#include "cobalt/math/rect.h"
#include "cobalt/math/size.h"
#include "cobalt/render_tree/image.h"
#include "cobalt/render_tree/resource_provider.h"
#include "starboard/decode_target.h"
#include "third_party/skia/include/core/SkImage.h"

namespace cobalt {
namespace renderer {

namespace backend {
class TextureEGL;
}  // namespace backend

namespace rasterizer {
namespace skia {

// Introduce a base class for both software and hardware Skia images.  They
// should both be able to return a SkBitmap that can be used in subsequent
// Skia draw calls.
class Image : public render_tree::Image {
 public:
  // Ensures that any queued backend initialization of this image object is
  // completed after this method returns.  This can only be called from the
  // rasterizer thread.  When an Image is created (from any thread), the
  // construction of its backend is message queued to be initialized on the
  // render thread, however it is possible (via animations) for the image
  // to be referenced in a render tree before then, and thus this function will
  // fast-track the initialization of the backend object if it has not yet
  // executed.
  // Returns true if an initialization actually took place.
  virtual bool EnsureInitialized() = 0;

  // Mechanism to allow dynamic type checking on Image objects.
  virtual base::TypeId GetTypeId() const = 0;

  // A helper function for DCHECKing that given image data is indeed in
  // premultiplied alpha format.  Note that because of the nature of
  // premultiplied alpha, it is possible for a non-premultiplied alpha image
  // to slip by these checks.
  static void DCheckForPremultipliedAlpha(const math::Size& dimensions,
                                          int source_pitch_in_bytes,
                                          render_tree::PixelFormat pixel_format,
                                          const uint8_t* source_pixels);

  // While of course most skia::Image objects can be rendered in Skia, sometimes
  // this is not true, such as when they are backed by SbDecodeTarget objects
  // that assume a specific rasterizer such as GLES2.  In this case, we can
  // fallback to a rasterizer-provided renderer function.
  virtual bool CanRenderInSkia() const { return true; }
};

// A single-plane image is an image where all data to describe a single pixel
// is stored contiguously.  This style of image is by far the most common.
class SinglePlaneImage : public Image {
 public:
  virtual const sk_sp<SkImage>& GetImage() const = 0;

  base::TypeId GetTypeId() const override {
    return base::GetTypeId<SinglePlaneImage>();
  }

  // If GLES2 is backing this image, this function can be called to return a
  // reference to that EGL texture.
  virtual const backend::TextureEGL* GetTextureEGL() const { return NULL; }

  // If not-null, indicates a rectangle within the image in which the valid
  // pixel data is to be found.
  virtual const math::Rect* GetContentRegion() const { return NULL; }
};

// A multi-plane image is one where different channels may have different planes
// (i.e. sub-images) stored in different regions of memory.  A multi-plane
// image can be defined in terms of a set of single-plane images.
class MultiPlaneImage : public Image {
 public:
  virtual render_tree::MultiPlaneImageFormat GetFormat() const = 0;
  virtual const backend::TextureEGL* GetTextureEGL(int plane_index) const {
    return NULL;
  }

  base::TypeId GetTypeId() const override {
    return base::GetTypeId<MultiPlaneImage>();
  }

  // All currently supported MultiPlaneImage formats do not feature alpha.
  bool IsOpaque() const override { return true; }
};

}  // namespace skia
}  // namespace rasterizer
}  // namespace renderer
}  // namespace cobalt

#endif  // COBALT_RENDERER_RASTERIZER_SKIA_IMAGE_H_