/* vim:set sw=2 sts=2 et cin: */
/* 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/. */

#include <gdk-pixbuf/gdk-pixbuf.h>

#include "nsImageToPixbuf.h"

#include "imgIContainer.h"
#include "mozilla/gfx/2D.h"
#include "mozilla/RefPtr.h"

using mozilla::gfx::DataSourceSurface;
using mozilla::gfx::SurfaceFormat;

NS_IMPL_ISUPPORTS(nsImageToPixbuf, nsIImageToPixbuf)

inline unsigned char unpremultiply(unsigned char color, unsigned char alpha) {
  if (alpha == 0) return 0;
  // plus alpha/2 to round instead of truncate
  return (color * 255 + alpha / 2) / alpha;
}

NS_IMETHODIMP_(GdkPixbuf*)
nsImageToPixbuf::ConvertImageToPixbuf(imgIContainer* aImage) {
  return ImageToPixbuf(aImage);
}

GdkPixbuf* nsImageToPixbuf::ImageToPixbuf(imgIContainer* aImage) {
  RefPtr<SourceSurface> surface = aImage->GetFrame(
      imgIContainer::FRAME_CURRENT, imgIContainer::FLAG_SYNC_DECODE);

  // If the last call failed, it was probably because our call stack originates
  // in an imgINotificationObserver event, meaning that we're not allowed
  // request a sync decode. Presumably the originating event is something
  // sensible like OnStopFrame(), so we can just retry the call without a sync
  // decode.
  if (!surface)
    surface = aImage->GetFrame(imgIContainer::FRAME_CURRENT,
                               imgIContainer::FLAG_NONE);

  NS_ENSURE_TRUE(surface, nullptr);

  return SourceSurfaceToPixbuf(surface, surface->GetSize().width,
                               surface->GetSize().height);
}

GdkPixbuf* nsImageToPixbuf::SourceSurfaceToPixbuf(SourceSurface* aSurface,
                                                  int32_t aWidth,
                                                  int32_t aHeight) {
  MOZ_ASSERT(aWidth <= aSurface->GetSize().width &&
                 aHeight <= aSurface->GetSize().height,
             "Requested rect is bigger than the supplied surface");

  GdkPixbuf* pixbuf =
      gdk_pixbuf_new(GDK_COLORSPACE_RGB, TRUE, 8, aWidth, aHeight);
  if (!pixbuf) return nullptr;

  uint32_t destStride = gdk_pixbuf_get_rowstride(pixbuf);
  guchar* destPixels = gdk_pixbuf_get_pixels(pixbuf);

  RefPtr<DataSourceSurface> dataSurface = aSurface->GetDataSurface();
  DataSourceSurface::MappedSurface map;
  if (!dataSurface->Map(DataSourceSurface::MapType::READ, &map)) return nullptr;

  uint8_t* srcData = map.mData;
  int32_t srcStride = map.mStride;

  SurfaceFormat format = dataSurface->GetFormat();

  for (int32_t row = 0; row < aHeight; ++row) {
    for (int32_t col = 0; col < aWidth; ++col) {
      guchar* destPixel = destPixels + row * destStride + 4 * col;

      uint32_t* srcPixel =
          reinterpret_cast<uint32_t*>((srcData + row * srcStride + 4 * col));

      if (format == SurfaceFormat::B8G8R8A8) {
        const uint8_t a = (*srcPixel >> 24) & 0xFF;
        const uint8_t r = unpremultiply((*srcPixel >> 16) & 0xFF, a);
        const uint8_t g = unpremultiply((*srcPixel >> 8) & 0xFF, a);
        const uint8_t b = unpremultiply((*srcPixel >> 0) & 0xFF, a);

        *destPixel++ = r;
        *destPixel++ = g;
        *destPixel++ = b;
        *destPixel++ = a;
      } else {
        MOZ_ASSERT(format == SurfaceFormat::B8G8R8X8);

        const uint8_t r = (*srcPixel >> 16) & 0xFF;
        const uint8_t g = (*srcPixel >> 8) & 0xFF;
        const uint8_t b = (*srcPixel >> 0) & 0xFF;

        *destPixel++ = r;
        *destPixel++ = g;
        *destPixel++ = b;
        *destPixel++ = 0xFF;  // A
      }
    }
  }

  dataSurface->Unmap();

  return pixbuf;
}
