root/printing/emf_win.cc

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DEFINITIONS

This source file includes following definitions.
  1. IsAlphaBlendUsedEnumProc
  2. RasterizeAlphaBlendProc
  3. context
  4. DIBFormatNativelySupported
  5. page_count_
  6. InitToFile
  7. InitFromFile
  8. Init
  9. InitFromData
  10. FinishDocument
  11. Playback
  12. SafePlayback
  13. GetPageBounds
  14. GetDataSize
  15. GetData
  16. GetDataAsVector
  17. SaveTo
  18. SafePlaybackProc
  19. Play
  20. SafePlayback
  21. StartPageForVectorCanvas
  22. StartPage
  23. FinishPage
  24. begin
  25. end
  26. EnhMetaFileProc
  27. IsAlphaBlendUsed
  28. RasterizeMetafile
  29. RasterizeAlphaBlend

// Copyright (c) 2012 The Chromium 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 "printing/emf_win.h"

#include "base/files/file_path.h"
#include "base/logging.h"
#include "base/memory/scoped_ptr.h"
#include "base/win/scoped_gdi_object.h"
#include "base/win/scoped_hdc.h"
#include "base/win/scoped_select_object.h"
#include "skia/ext/vector_platform_device_emf_win.h"
#include "third_party/skia/include/core/SkBitmap.h"
#include "ui/gfx/codec/jpeg_codec.h"
#include "ui/gfx/codec/png_codec.h"
#include "ui/gfx/gdi_util.h"
#include "ui/gfx/rect.h"
#include "ui/gfx/size.h"

namespace {

const int kCustomGdiCommentSignature = 0xdeadbabe;
struct PageBreakRecord {
  int signature;
  enum PageBreakType {
    START_PAGE,
    END_PAGE,
  } type;
  explicit PageBreakRecord(PageBreakType type_in)
      : signature(kCustomGdiCommentSignature), type(type_in) {
  }
  bool IsValid() const {
    return (signature == kCustomGdiCommentSignature) &&
           (type >= START_PAGE) && (type <= END_PAGE);
  }
};

int CALLBACK IsAlphaBlendUsedEnumProc(HDC,
                                      HANDLETABLE*,
                                      const ENHMETARECORD *record,
                                      int,
                                      LPARAM data) {
  bool* result = reinterpret_cast<bool*>(data);
  if (!result)
    return 0;
  switch (record->iType) {
    case EMR_ALPHABLEND: {
      *result = true;
      return 0;
      break;
    }
  }
  return 1;
}

int CALLBACK RasterizeAlphaBlendProc(HDC metafile_dc,
                                     HANDLETABLE* handle_table,
                                     const ENHMETARECORD *record,
                                     int num_objects,
                                     LPARAM data) {
    HDC bitmap_dc = *reinterpret_cast<HDC*>(data);
    // Play this command to the bitmap DC.
    ::PlayEnhMetaFileRecord(bitmap_dc, handle_table, record, num_objects);
    switch (record->iType) {
    case EMR_ALPHABLEND: {
      const EMRALPHABLEND* alpha_blend =
          reinterpret_cast<const EMRALPHABLEND*>(record);
      // Don't modify transformation here.
      // Old implementation did reset transformations for DC to identity matrix.
      // That was not correct and cause some bugs, like unexpected cropping.
      // EMRALPHABLEND is rendered into bitmap and metafile contexts with
      // current transformation. If we don't touch them here BitBlt will copy
      // same areas.
      ::BitBlt(metafile_dc,
               alpha_blend->xDest,
               alpha_blend->yDest,
               alpha_blend->cxDest,
               alpha_blend->cyDest,
               bitmap_dc,
               alpha_blend->xDest,
               alpha_blend->yDest,
               SRCCOPY);
      break;
    }
    case EMR_CREATEBRUSHINDIRECT:
    case EMR_CREATECOLORSPACE:
    case EMR_CREATECOLORSPACEW:
    case EMR_CREATEDIBPATTERNBRUSHPT:
    case EMR_CREATEMONOBRUSH:
    case EMR_CREATEPALETTE:
    case EMR_CREATEPEN:
    case EMR_DELETECOLORSPACE:
    case EMR_DELETEOBJECT:
    case EMR_EXTCREATEFONTINDIRECTW:
      // Play object creation command only once.
      break;

    default:
      // Play this command to the metafile DC.
      ::PlayEnhMetaFileRecord(metafile_dc, handle_table, record, num_objects);
      break;
    }
    return 1;  // Continue enumeration
}

// Bitmapt for rasterization.
class RasterBitmap {
 public:
  explicit RasterBitmap(const gfx::Size& raster_size)
      : saved_object_(NULL) {
    context_.Set(::CreateCompatibleDC(NULL));
    if (!context_) {
      NOTREACHED() << "Bitmap DC creation failed";
      return;
    }
    ::SetGraphicsMode(context_, GM_ADVANCED);
    void* bits = NULL;
    gfx::Rect bitmap_rect(raster_size);
    gfx::CreateBitmapHeader(raster_size.width(), raster_size.height(),
                            &header_.bmiHeader);
    bitmap_.Set(::CreateDIBSection(context_, &header_, DIB_RGB_COLORS, &bits,
                                   NULL, 0));
    if (!bitmap_)
      NOTREACHED() << "Raster bitmap creation for printing failed";

    saved_object_ = ::SelectObject(context_, bitmap_);
    RECT rect = bitmap_rect.ToRECT();
    ::FillRect(context_, &rect,
               static_cast<HBRUSH>(::GetStockObject(WHITE_BRUSH)));

  }

  ~RasterBitmap() {
    ::SelectObject(context_, saved_object_);
  }

  HDC context() const {
    return context_;
  }

  base::win::ScopedCreateDC context_;
  BITMAPINFO header_;
  base::win::ScopedBitmap bitmap_;
  HGDIOBJ saved_object_;

 private:
  DISALLOW_COPY_AND_ASSIGN(RasterBitmap);
};



}  // namespace

namespace printing {

bool DIBFormatNativelySupported(HDC dc, uint32 escape, const BYTE* bits,
                                int size) {
  BOOL supported = FALSE;
  if (ExtEscape(dc, QUERYESCSUPPORT, sizeof(escape),
                reinterpret_cast<LPCSTR>(&escape), 0, 0) > 0) {
    ExtEscape(dc, escape, size, reinterpret_cast<LPCSTR>(bits),
              sizeof(supported), reinterpret_cast<LPSTR>(&supported));
  }
  return !!supported;
}

Emf::Emf() : emf_(NULL), hdc_(NULL), page_count_(0) {
}

Emf::~Emf() {
  DCHECK(!hdc_);
  if (emf_)
    DeleteEnhMetaFile(emf_);
}

bool Emf::InitToFile(const base::FilePath& metafile_path) {
  DCHECK(!emf_ && !hdc_);
  hdc_ = CreateEnhMetaFile(NULL, metafile_path.value().c_str(), NULL, NULL);
  DCHECK(hdc_);
  return hdc_ != NULL;
}

bool Emf::InitFromFile(const base::FilePath& metafile_path) {
  DCHECK(!emf_ && !hdc_);
  emf_ = GetEnhMetaFile(metafile_path.value().c_str());
  DCHECK(emf_);
  return emf_ != NULL;
}

bool Emf::Init() {
  DCHECK(!emf_ && !hdc_);
  hdc_ = CreateEnhMetaFile(NULL, NULL, NULL, NULL);
  DCHECK(hdc_);
  return hdc_ != NULL;
}

bool Emf::InitFromData(const void* src_buffer, uint32 src_buffer_size) {
  DCHECK(!emf_ && !hdc_);
  emf_ = SetEnhMetaFileBits(src_buffer_size,
                            reinterpret_cast<const BYTE*>(src_buffer));
  return emf_ != NULL;
}

bool Emf::FinishDocument() {
  DCHECK(!emf_ && hdc_);
  emf_ = CloseEnhMetaFile(hdc_);
  DCHECK(emf_);
  hdc_ = NULL;
  return emf_ != NULL;
}

bool Emf::Playback(HDC hdc, const RECT* rect) const {
  DCHECK(emf_ && !hdc_);
  RECT bounds;
  if (!rect) {
    // Get the natural bounds of the EMF buffer.
    bounds = GetPageBounds(1).ToRECT();
    rect = &bounds;
  }
  return PlayEnhMetaFile(hdc, emf_, rect) != 0;
}

bool Emf::SafePlayback(HDC context) const {
  DCHECK(emf_ && !hdc_);
  XFORM base_matrix;
  if (!GetWorldTransform(context, &base_matrix)) {
    NOTREACHED();
    return false;
  }
  Emf::EnumerationContext playback_context;
  playback_context.base_matrix = &base_matrix;
  RECT rect = GetPageBounds(1).ToRECT();
  return EnumEnhMetaFile(context,
                         emf_,
                         &Emf::SafePlaybackProc,
                         reinterpret_cast<void*>(&playback_context),
                         &rect) != 0;
}

gfx::Rect Emf::GetPageBounds(unsigned int page_number) const {
  DCHECK(emf_ && !hdc_);
  DCHECK_EQ(1U, page_number);
  ENHMETAHEADER header;
  if (GetEnhMetaFileHeader(emf_, sizeof(header), &header) != sizeof(header)) {
    NOTREACHED();
    return gfx::Rect();
  }
  // Add 1 to right and bottom because it's inclusive rectangle.
  // See ENHMETAHEADER.
  return gfx::Rect(header.rclBounds.left,
                   header.rclBounds.top,
                   header.rclBounds.right - header.rclBounds.left + 1,
                   header.rclBounds.bottom - header.rclBounds.top + 1);
}

uint32 Emf::GetDataSize() const {
  DCHECK(emf_ && !hdc_);
  return GetEnhMetaFileBits(emf_, 0, NULL);
}

bool Emf::GetData(void* buffer, uint32 size) const {
  DCHECK(emf_ && !hdc_);
  DCHECK(buffer && size);
  uint32 size2 =
      GetEnhMetaFileBits(emf_, size, reinterpret_cast<BYTE*>(buffer));
  DCHECK(size2 == size);
  return size2 == size && size2 != 0;
}

bool Emf::GetDataAsVector(std::vector<uint8>* buffer) const {
  uint32 size = GetDataSize();
  if (!size)
    return false;

  buffer->resize(size);
  if (!GetData(&buffer->front(), size))
    return false;
  return true;
}

bool Emf::SaveTo(const base::FilePath& file_path) const {
  HANDLE file = CreateFile(file_path.value().c_str(), GENERIC_WRITE,
                           FILE_SHARE_READ | FILE_SHARE_WRITE, NULL,
                           CREATE_ALWAYS, 0, NULL);
  if (file == INVALID_HANDLE_VALUE)
    return false;

  bool success = false;
  std::vector<uint8> buffer;
  if (GetDataAsVector(&buffer)) {
    DWORD written = 0;
    if (WriteFile(file, &*buffer.begin(), static_cast<DWORD>(buffer.size()),
                  &written, NULL) &&
        written == buffer.size()) {
      success = true;
    }
  }
  CloseHandle(file);
  return success;
}

int CALLBACK Emf::SafePlaybackProc(HDC hdc,
                                   HANDLETABLE* handle_table,
                                   const ENHMETARECORD* record,
                                   int objects_count,
                                   LPARAM param) {
  Emf::EnumerationContext* context =
      reinterpret_cast<Emf::EnumerationContext*>(param);
  context->handle_table = handle_table;
  context->objects_count = objects_count;
  context->hdc = hdc;
  Record record_instance(record);
  bool success = record_instance.SafePlayback(context);
  DCHECK(success);
  return 1;
}

Emf::EnumerationContext::EnumerationContext() {
  memset(this, 0, sizeof(*this));
}

Emf::Record::Record(const ENHMETARECORD* record)
    : record_(record) {
  DCHECK(record_);
}

bool Emf::Record::Play(Emf::EnumerationContext* context) const {
  return 0 != PlayEnhMetaFileRecord(context->hdc,
                                    context->handle_table,
                                    record_,
                                    context->objects_count);
}

bool Emf::Record::SafePlayback(Emf::EnumerationContext* context) const {
  // For EMF field description, see [MS-EMF] Enhanced Metafile Format
  // Specification.
  //
  // This is the second major EMF breakage I get; the first one being
  // SetDCBrushColor/SetDCPenColor/DC_PEN/DC_BRUSH being silently ignored.
  //
  // This function is the guts of the fix for bug 1186598. Some printer drivers
  // somehow choke on certain EMF records, but calling the corresponding
  // function directly on the printer HDC is fine. Still, playing the EMF record
  // fails. Go figure.
  //
  // The main issue is that SetLayout is totally unsupported on these printers
  // (HP 4500/4700). I used to call SetLayout and I stopped. I found out this is
  // not sufficient because GDI32!PlayEnhMetaFile internally calls SetLayout(!)
  // Damn.
  //
  // So I resorted to manually parse the EMF records and play them one by one.
  // The issue with this method compared to using PlayEnhMetaFile to play back
  // an EMF buffer is that the later silently fixes the matrix to take in
  // account the matrix currently loaded at the time of the call.
  // The matrix magic is done transparently when using PlayEnhMetaFile but since
  // I'm processing one field at a time, I need to do the fixup myself. Note
  // that PlayEnhMetaFileRecord doesn't fix the matrix correctly even when
  // called inside an EnumEnhMetaFile loop. Go figure (bis).
  //
  // So when I see a EMR_SETWORLDTRANSFORM and EMR_MODIFYWORLDTRANSFORM, I need
  // to fix the matrix according to the matrix previously loaded before playing
  // back the buffer. Otherwise, the previously loaded matrix would be ignored
  // and the EMF buffer would always be played back at its native resolution.
  // Duh.
  //
  // I also use this opportunity to skip over eventual EMR_SETLAYOUT record that
  // could remain.
  //
  // Another tweak we make is for JPEGs/PNGs in calls to StretchDIBits.
  // (Our Pepper plugin code uses a JPEG). If the printer does not support
  // JPEGs/PNGs natively we decompress the JPEG/PNG and then set it to the
  // device.
  // TODO(sanjeevr): We should also add JPEG/PNG support for SetSIBitsToDevice
  //
  // We also process any custom EMR_GDICOMMENT records which are our
  // placeholders for StartPage and EndPage.
  // Note: I should probably care about view ports and clipping, eventually.
  bool res = false;
  const XFORM* base_matrix = context->base_matrix;
  switch (record()->iType) {
    case EMR_STRETCHDIBITS: {
      const EMRSTRETCHDIBITS * sdib_record =
          reinterpret_cast<const EMRSTRETCHDIBITS*>(record());
      const BYTE* record_start = reinterpret_cast<const BYTE *>(record());
      const BITMAPINFOHEADER *bmih =
          reinterpret_cast<const BITMAPINFOHEADER *>(record_start +
                                                     sdib_record->offBmiSrc);
      const BYTE* bits = record_start + sdib_record->offBitsSrc;
      bool play_normally = true;
      res = false;
      HDC hdc = context->hdc;
      scoped_ptr<SkBitmap> bitmap;
      if (bmih->biCompression == BI_JPEG) {
        if (!DIBFormatNativelySupported(hdc, CHECKJPEGFORMAT, bits,
                                        bmih->biSizeImage)) {
          play_normally = false;
          bitmap.reset(gfx::JPEGCodec::Decode(bits, bmih->biSizeImage));
        }
      } else if (bmih->biCompression == BI_PNG) {
        if (!DIBFormatNativelySupported(hdc, CHECKPNGFORMAT, bits,
                                        bmih->biSizeImage)) {
          play_normally = false;
          bitmap.reset(new SkBitmap());
          gfx::PNGCodec::Decode(bits, bmih->biSizeImage, bitmap.get());
        }
      }
      if (!play_normally) {
        DCHECK(bitmap.get());
        if (bitmap.get()) {
          SkAutoLockPixels lock(*bitmap.get());
          DCHECK_EQ(bitmap->config(), SkBitmap::kARGB_8888_Config);
          const uint32_t* pixels =
              static_cast<const uint32_t*>(bitmap->getPixels());
          if (pixels == NULL) {
            NOTREACHED();
            return false;
          }
          BITMAPINFOHEADER bmi = {0};
          gfx::CreateBitmapHeader(bitmap->width(), bitmap->height(), &bmi);
          res = (0 != StretchDIBits(hdc, sdib_record->xDest, sdib_record->yDest,
                                    sdib_record->cxDest,
                                    sdib_record->cyDest, sdib_record->xSrc,
                                    sdib_record->ySrc,
                                    sdib_record->cxSrc, sdib_record->cySrc,
                                    pixels,
                                    reinterpret_cast<const BITMAPINFO *>(&bmi),
                                    sdib_record->iUsageSrc,
                                    sdib_record->dwRop));
        }
      } else {
        res = Play(context);
      }
      break;
    }
    case EMR_SETWORLDTRANSFORM: {
      DCHECK_EQ(record()->nSize, sizeof(DWORD) * 2 + sizeof(XFORM));
      const XFORM* xform = reinterpret_cast<const XFORM*>(record()->dParm);
      HDC hdc = context->hdc;
      if (base_matrix) {
        res = 0 != SetWorldTransform(hdc, base_matrix) &&
                   ModifyWorldTransform(hdc, xform, MWT_LEFTMULTIPLY);
      } else {
        res = 0 != SetWorldTransform(hdc, xform);
      }
      break;
    }
    case EMR_MODIFYWORLDTRANSFORM: {
      DCHECK_EQ(record()->nSize,
                sizeof(DWORD) * 2 + sizeof(XFORM) + sizeof(DWORD));
      const XFORM* xform = reinterpret_cast<const XFORM*>(record()->dParm);
      const DWORD* option = reinterpret_cast<const DWORD*>(xform + 1);
      HDC hdc = context->hdc;
      switch (*option) {
        case MWT_IDENTITY:
          if (base_matrix) {
            res = 0 != SetWorldTransform(hdc, base_matrix);
          } else {
            res = 0 != ModifyWorldTransform(hdc, xform, MWT_IDENTITY);
          }
          break;
        case MWT_LEFTMULTIPLY:
        case MWT_RIGHTMULTIPLY:
          res = 0 != ModifyWorldTransform(hdc, xform, *option);
          break;
        case 4:  // MWT_SET
          if (base_matrix) {
            res = 0 != SetWorldTransform(hdc, base_matrix) &&
                       ModifyWorldTransform(hdc, xform, MWT_LEFTMULTIPLY);
          } else {
            res = 0 != SetWorldTransform(hdc, xform);
          }
          break;
        default:
          res = false;
          break;
      }
      break;
    }
    case EMR_SETLAYOUT:
      // Ignore it.
      res = true;
      break;
    case EMR_GDICOMMENT: {
      const EMRGDICOMMENT* comment_record =
          reinterpret_cast<const EMRGDICOMMENT*>(record());
      if (comment_record->cbData == sizeof(PageBreakRecord)) {
        const PageBreakRecord* page_break_record =
            reinterpret_cast<const PageBreakRecord*>(comment_record->Data);
        if (page_break_record && page_break_record->IsValid()) {
          if (page_break_record->type == PageBreakRecord::START_PAGE) {
            res = !!::StartPage(context->hdc);
            DCHECK_EQ(0, context->dc_on_page_start);
            context->dc_on_page_start = ::SaveDC(context->hdc);
          } else if (page_break_record->type == PageBreakRecord::END_PAGE) {
            DCHECK_NE(0, context->dc_on_page_start);
            ::RestoreDC(context->hdc, context->dc_on_page_start);
            context->dc_on_page_start = 0;
            res = !!::EndPage(context->hdc);
          } else {
            res = false;
            NOTREACHED();
          }
        } else {
          res = Play(context);
        }
      } else {
        res = true;
      }
      break;
    }
    default: {
      res = Play(context);
      break;
    }
  }
  return res;
}

SkBaseDevice* Emf::StartPageForVectorCanvas(
    const gfx::Size& page_size, const gfx::Rect& content_area,
    const float& scale_factor) {
  if (!StartPage(page_size, content_area, scale_factor))
    return NULL;

  return skia::VectorPlatformDeviceEmf::CreateDevice(page_size.width(),
                                                     page_size.height(),
                                                     true, hdc_);
}

bool Emf::StartPage(const gfx::Size& /*page_size*/,
                    const gfx::Rect& /*content_area*/,
                    const float& /*scale_factor*/) {
  DCHECK(hdc_);
  if (!hdc_)
    return false;
  page_count_++;
  PageBreakRecord record(PageBreakRecord::START_PAGE);
  return !!GdiComment(hdc_, sizeof(record),
                      reinterpret_cast<const BYTE *>(&record));
}

bool Emf::FinishPage() {
  DCHECK(hdc_);
  if (!hdc_)
    return false;
  PageBreakRecord record(PageBreakRecord::END_PAGE);
  return !!GdiComment(hdc_, sizeof(record),
                      reinterpret_cast<const BYTE *>(&record));
}

Emf::Enumerator::Enumerator(const Emf& emf, HDC context, const RECT* rect) {
  items_.clear();
  if (!EnumEnhMetaFile(context,
                       emf.emf(),
                       &Emf::Enumerator::EnhMetaFileProc,
                       reinterpret_cast<void*>(this),
                       rect)) {
    NOTREACHED();
    items_.clear();
  }
  DCHECK_EQ(context_.hdc, context);
}

Emf::Enumerator::const_iterator Emf::Enumerator::begin() const {
  return items_.begin();
}

Emf::Enumerator::const_iterator Emf::Enumerator::end() const {
  return items_.end();
}

int CALLBACK Emf::Enumerator::EnhMetaFileProc(HDC hdc,
                                              HANDLETABLE* handle_table,
                                              const ENHMETARECORD* record,
                                              int objects_count,
                                              LPARAM param) {
  Enumerator& emf = *reinterpret_cast<Enumerator*>(param);
  if (!emf.context_.handle_table) {
    DCHECK(!emf.context_.handle_table);
    DCHECK(!emf.context_.objects_count);
    emf.context_.handle_table = handle_table;
    emf.context_.objects_count = objects_count;
    emf.context_.hdc = hdc;
  } else {
    DCHECK_EQ(emf.context_.handle_table, handle_table);
    DCHECK_EQ(emf.context_.objects_count, objects_count);
    DCHECK_EQ(emf.context_.hdc, hdc);
  }
  emf.items_.push_back(Record(record));
  return 1;
}

bool Emf::IsAlphaBlendUsed() const {
  bool result = false;
  ::EnumEnhMetaFile(NULL,
                    emf(),
                    &IsAlphaBlendUsedEnumProc,
                    &result,
                    NULL);
  return result;
}

Emf* Emf::RasterizeMetafile(int raster_area_in_pixels) const {
  gfx::Rect page_bounds = GetPageBounds(1);
  gfx::Size page_size(page_bounds.size());
  if (page_size.GetArea() <= 0) {
    NOTREACHED() << "Metafile is empty";
    page_bounds = gfx::Rect(1, 1);
  }

  float scale = sqrt(float(raster_area_in_pixels) / page_size.GetArea());
  page_size.set_width(std::max<int>(1, page_size.width() * scale));
  page_size.set_height(std::max<int>(1, page_size.height() * scale));


  RasterBitmap bitmap(page_size);

  gfx::Rect bitmap_rect(page_size);
  RECT rect = bitmap_rect.ToRECT();
  Playback(bitmap.context(), &rect);

  scoped_ptr<Emf> result(new Emf);
  result->Init();
  HDC hdc = result->context();
  DCHECK(hdc);
  skia::InitializeDC(hdc);

  // Params are ignored.
  result->StartPage(page_bounds.size(), page_bounds, 1);

  ::ModifyWorldTransform(hdc, NULL, MWT_IDENTITY);
  XFORM xform = {
    float(page_bounds.width()) / bitmap_rect.width(), 0,
    0, float(page_bounds.height()) / bitmap_rect.height(),
    page_bounds.x(),
    page_bounds.y(),
  };
  ::SetWorldTransform(hdc, &xform);
  ::BitBlt(hdc, 0, 0, bitmap_rect.width(), bitmap_rect.height(),
           bitmap.context(), bitmap_rect.x(), bitmap_rect.y(), SRCCOPY);

  result->FinishPage();
  result->FinishDocument();

  return result.release();
}

Emf* Emf::RasterizeAlphaBlend() const {
  gfx::Rect page_bounds = GetPageBounds(1);
  if (page_bounds.size().GetArea() <= 0) {
    NOTREACHED() << "Metafile is empty";
    page_bounds = gfx::Rect(1, 1);
  }

  RasterBitmap bitmap(page_bounds.size());

  // Map metafile page_bounds.x(), page_bounds.y() to bitmap 0, 0.
  XFORM xform = { 1, 0, 0, 1, -page_bounds.x(), -page_bounds.y()};
  ::SetWorldTransform(bitmap.context(), &xform);

  scoped_ptr<Emf> result(new Emf);
  result->Init();
  HDC hdc = result->context();
  DCHECK(hdc);
  skia::InitializeDC(hdc);

  HDC bitmap_dc = bitmap.context();
  RECT rect = page_bounds.ToRECT();
  ::EnumEnhMetaFile(hdc, emf(), &RasterizeAlphaBlendProc, &bitmap_dc, &rect);

  result->FinishDocument();

  return result.release();
}


}  // namespace printing

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