chrome/utility/cloud_print/pwg_encoder.cc - chromium/chromium - Git at Google

 // Copyright 2013 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 "chrome/utility/cloud_print/pwg_encoder.h"

 #include <algorithm>

 #include "base/big_endian.h"
 #include "base/logging.h"
 #include "base/memory/scoped_ptr.h"
 #include "chrome/utility/cloud_print/bitmap_image.h"

 namespace cloud_print {

 namespace {

 const uint32 kBitsPerColor = 8;
 const uint32 kColorOrder = 0;  // chunky.

 // Coefficients used to convert from RGB to monochrome.
 const uint32 kRedCoefficient = 2125;
 const uint32 kGreenCoefficient = 7154;
 const uint32 kBlueCoefficient = 0721;
 const uint32 kColorCoefficientDenominator = 10000;

 const char* kPwgKeyword = "RaS2";

 const uint32 kHeaderSize = 1796;
 const uint32 kHeaderCupsDuplex = 272;
 const uint32 kHeaderCupsHwResolutionHorizontal = 276;
 const uint32 kHeaderCupsHwResolutionVertical = 280;
 const uint32 kHeaderCupsTumble = 368;
 const uint32 kHeaderCupsWidth = 372;
 const uint32 kHeaderCupsHeight = 376;
 const uint32 kHeaderCupsBitsPerColor = 384;
 const uint32 kHeaderCupsBitsPerPixel = 388;
 const uint32 kHeaderCupsBytesPerLine = 392;
 const uint32 kHeaderCupsColorOrder = 396;
 const uint32 kHeaderCupsColorSpace = 400;
 const uint32 kHeaderCupsNumColors = 420;
 const uint32 kHeaderPwgTotalPageCount = 452;
 const uint32 kHeaderPwgCrossFeedTransform = 456;
 const uint32 kHeaderPwgFeedTransform = 460;

 const int kPwgMaxPackedRows = 256;

 const int kPwgMaxPackedPixels = 128;

 struct RGBA8 {
   uint8 red;
   uint8 green;
   uint8 blue;
   uint8 alpha;
 };

 struct BGRA8 {
   uint8 blue;
   uint8 green;
   uint8 red;
   uint8 alpha;
 };

 template <class InputStruct>
 inline void encodePixelToRGB(const void* pixel, std::string* output) {
   const InputStruct* i = reinterpret_cast<const InputStruct*>(pixel);
   output->push_back(static_cast<char>(i->red));
   output->push_back(static_cast<char>(i->green));
   output->push_back(static_cast<char>(i->blue));
 }

 template <class InputStruct>
 inline void encodePixelToMonochrome(const void* pixel, std::string* output) {
   const InputStruct* i = reinterpret_cast<const InputStruct*>(pixel);
   output->push_back(static_cast<char>((i->red * kRedCoefficient +
                                        i->green * kGreenCoefficient +
                                        i->blue * kBlueCoefficient) /
                                       kColorCoefficientDenominator));
 }

 }  // namespace

 PwgEncoder::PwgEncoder() {}

 void PwgEncoder::EncodeDocumentHeader(std::string* output) const {
   output->clear();
   output->append(kPwgKeyword, 4);
 }

 void PwgEncoder::EncodePageHeader(const BitmapImage& image,
                                   const PwgHeaderInfo& pwg_header_info,
                                   std::string* output) const {
   char header[kHeaderSize];
   memset(header, 0, kHeaderSize);

   uint32 num_colors =
       pwg_header_info.color_space == PwgHeaderInfo::SGRAY ? 1 : 3;
   uint32 bits_per_pixel = num_colors * kBitsPerColor;

   base::WriteBigEndian<uint32>(header + kHeaderCupsDuplex,
                                pwg_header_info.duplex ? 1 : 0);
   base::WriteBigEndian<uint32>(header + kHeaderCupsHwResolutionHorizontal,
                                pwg_header_info.dpi);
   base::WriteBigEndian<uint32>(header + kHeaderCupsHwResolutionVertical,
                                pwg_header_info.dpi);
   base::WriteBigEndian<uint32>(header + kHeaderCupsTumble,
                                pwg_header_info.tumble ? 1 : 0);
   base::WriteBigEndian<uint32>(header + kHeaderCupsWidth, image.size().width());
   base::WriteBigEndian<uint32>(header + kHeaderCupsHeight,
                                image.size().height());
   base::WriteBigEndian<uint32>(header + kHeaderCupsBitsPerColor, kBitsPerColor);
   base::WriteBigEndian<uint32>(header + kHeaderCupsBitsPerPixel,
                                bits_per_pixel);
   base::WriteBigEndian<uint32>(header + kHeaderCupsBytesPerLine,
                                (bits_per_pixel * image.size().width() + 7) / 8);
   base::WriteBigEndian<uint32>(header + kHeaderCupsColorOrder, kColorOrder);
   base::WriteBigEndian<uint32>(header + kHeaderCupsColorSpace,
                                pwg_header_info.color_space);
   base::WriteBigEndian<uint32>(header + kHeaderCupsNumColors, num_colors);
   base::WriteBigEndian<uint32>(header + kHeaderPwgCrossFeedTransform,
                                pwg_header_info.flipx ? -1 : 1);
   base::WriteBigEndian<uint32>(header + kHeaderPwgFeedTransform,
                                pwg_header_info.flipy ? -1 : 1);
   base::WriteBigEndian<uint32>(header + kHeaderPwgTotalPageCount,
                                pwg_header_info.total_pages);
   output->append(header, kHeaderSize);
 }

 template <typename InputStruct, class RandomAccessIterator>
 void PwgEncoder::EncodeRow(RandomAccessIterator pos,
                            RandomAccessIterator row_end,
                            bool monochrome,
                            std::string* output) const {
   // According to PWG-raster, a sequence of N identical pixels (up to 128)
   // can be encoded by a byte N-1, followed by the information on
   // that pixel. Any generic sequence of N pixels (up to 129) can be encoded
   // with (signed) byte 1-N, followed by the information on the N pixels.
   // Notice that for sequences of 1 pixel there is no difference between
   // the two encodings.

   // We encode every largest sequence of identical pixels together because it
   // usually saves the most space. Every other pixel should be encoded in the
   // smallest number of generic sequences.
   // NOTE: the algorithm is not optimal especially in case of monochrome.
   while (pos != row_end) {
     RandomAccessIterator it = pos + 1;
     RandomAccessIterator end = std::min(pos + kPwgMaxPackedPixels, row_end);

     // Counts how many identical pixels (up to 128).
     while (it != end && *pos == *it) {
       ++it;
     }
     if (it != pos + 1) {  // More than one pixel
       output->push_back(static_cast<char>((it - pos) - 1));
       if (monochrome)
         encodePixelToMonochrome<InputStruct>(&*pos, output);
       else
         encodePixelToRGB<InputStruct>(&*pos, output);
       pos = it;
     } else {
       // Finds how many pixels there are each different from the previous one.
       // IMPORTANT: even if sequences of different pixels can contain as many
       // as 129 pixels, we restrict to 128 because some decoders don't manage
       // it correctly. So iterating until it != end is correct.
       while (it != end && *it != *(it - 1)) {
         ++it;
       }
       // Optimization: ignores the last pixel of the sequence if it is followed
       // by an identical pixel, as it is more convenient for it to be the start
       // of a new sequence of identical pixels. Notice that we don't compare
       // to end, but row_end.
       if (it != row_end && *it == *(it - 1)) {
         --it;
       }
       output->push_back(static_cast<char>(1 - (it - pos)));
       while (pos != it) {
         if (monochrome)
           encodePixelToMonochrome<InputStruct>(&*pos, output);
         else
           encodePixelToRGB<InputStruct>(&*pos, output);
         ++pos;
       }
     }
   }
 }

 inline const uint8* PwgEncoder::GetRow(const BitmapImage& image,
                                        int row,
                                        bool flipy) const {
   return image.GetPixel(
       gfx::Point(0, flipy ? image.size().height() - 1 - row : row));
 }

 // Given a pointer to a struct Image, create a PWG of the image and
 // put the compressed image data in the string.  Returns true on success.
 // The content of the string is undefined on failure.
 bool PwgEncoder::EncodePage(const BitmapImage& image,
                             const PwgHeaderInfo& pwg_header_info,
                             std::string* output) const {
   // pwg_header_info.color_space can only contain color spaces that are
   // supported, so no sanity check is needed.
   switch (image.colorspace()) {
     case BitmapImage::RGBA:
       return EncodePageWithColorspace<RGBA8>(image, pwg_header_info, output);

     case BitmapImage::BGRA:
       return EncodePageWithColorspace<BGRA8>(image, pwg_header_info, output);

     default:
       LOG(ERROR) << "Unsupported colorspace.";
       return false;
   }
 }

 template <typename InputStruct>
 bool PwgEncoder::EncodePageWithColorspace(const BitmapImage& image,
                                           const PwgHeaderInfo& pwg_header_info,
                                           std::string* output) const {
   bool monochrome = pwg_header_info.color_space == PwgHeaderInfo::SGRAY;
   EncodePageHeader(image, pwg_header_info, output);

   // Ensure no integer overflow.
   CHECK(image.size().width() < INT_MAX / image.channels());
   int row_size = image.size().width() * image.channels();

   int row_number = 0;
   while (row_number < image.size().height()) {
     const uint8* current_row =
         GetRow(image, row_number++, pwg_header_info.flipy);
     int num_identical_rows = 1;
     // We count how many times the current row is repeated.
     while (num_identical_rows < kPwgMaxPackedRows &&
            row_number < image.size().height() &&
            !memcmp(current_row,
                    GetRow(image, row_number, pwg_header_info.flipy),
                    row_size)) {
       num_identical_rows++;
       row_number++;
     }
     output->push_back(static_cast<char>(num_identical_rows - 1));

     // Both supported colorspaces have a 32-bit pixels information.
     // Converts the list of uint8 to uint32 as every pixels contains 4 bytes
     // of information and comparison of elements is easier. The actual
     // Management of the bytes of the pixel is done by pixel_encoder function
     // on the original array to avoid endian problems.
     const uint32* pos = reinterpret_cast<const uint32*>(current_row);
     const uint32* row_end = pos + image.size().width();
     if (!pwg_header_info.flipx) {
       EncodeRow<InputStruct>(pos, row_end, monochrome, output);
     } else {
       // We reverse the iterators.
       EncodeRow<InputStruct>(std::reverse_iterator<const uint32*>(row_end),
                              std::reverse_iterator<const uint32*>(pos),
                              monochrome,
                              output);
     }
   }
   return true;
 }

 }  // namespace cloud_print
	// Copyright 2013 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 "chrome/utility/cloud_print/pwg_encoder.h"

	#include <algorithm>

	#include "base/big_endian.h"
	#include "base/logging.h"
	#include "base/memory/scoped_ptr.h"
	#include "chrome/utility/cloud_print/bitmap_image.h"

	namespace cloud_print {

	namespace {

	const uint32 kBitsPerColor = 8;
	const uint32 kColorOrder = 0; // chunky.

	// Coefficients used to convert from RGB to monochrome.
	const uint32 kRedCoefficient = 2125;
	const uint32 kGreenCoefficient = 7154;
	const uint32 kBlueCoefficient = 0721;
	const uint32 kColorCoefficientDenominator = 10000;

	const char* kPwgKeyword = "RaS2";

	const uint32 kHeaderSize = 1796;
	const uint32 kHeaderCupsDuplex = 272;
	const uint32 kHeaderCupsHwResolutionHorizontal = 276;
	const uint32 kHeaderCupsHwResolutionVertical = 280;
	const uint32 kHeaderCupsTumble = 368;
	const uint32 kHeaderCupsWidth = 372;
	const uint32 kHeaderCupsHeight = 376;
	const uint32 kHeaderCupsBitsPerColor = 384;
	const uint32 kHeaderCupsBitsPerPixel = 388;
	const uint32 kHeaderCupsBytesPerLine = 392;
	const uint32 kHeaderCupsColorOrder = 396;
	const uint32 kHeaderCupsColorSpace = 400;
	const uint32 kHeaderCupsNumColors = 420;
	const uint32 kHeaderPwgTotalPageCount = 452;
	const uint32 kHeaderPwgCrossFeedTransform = 456;
	const uint32 kHeaderPwgFeedTransform = 460;

	const int kPwgMaxPackedRows = 256;

	const int kPwgMaxPackedPixels = 128;

	struct RGBA8 {
	uint8 red;
	uint8 green;
	uint8 blue;
	uint8 alpha;
	};

	struct BGRA8 {
	uint8 blue;
	uint8 green;
	uint8 red;
	uint8 alpha;
	};

	template <class InputStruct>
	inline void encodePixelToRGB(const void* pixel, std::string* output) {
	const InputStruct* i = reinterpret_cast<const InputStruct*>(pixel);
	output->push_back(static_cast<char>(i->red));
	output->push_back(static_cast<char>(i->green));
	output->push_back(static_cast<char>(i->blue));
	}

	template <class InputStruct>
	inline void encodePixelToMonochrome(const void* pixel, std::string* output) {
	const InputStruct* i = reinterpret_cast<const InputStruct*>(pixel);
	output->push_back(static_cast<char>((i->red * kRedCoefficient +
	i->green * kGreenCoefficient +
	i->blue * kBlueCoefficient) /
	kColorCoefficientDenominator));
	}

	} // namespace

	PwgEncoder::PwgEncoder() {}

	void PwgEncoder::EncodeDocumentHeader(std::string* output) const {
	output->clear();
	output->append(kPwgKeyword, 4);
	}

	void PwgEncoder::EncodePageHeader(const BitmapImage& image,
	const PwgHeaderInfo& pwg_header_info,
	std::string* output) const {
	char header[kHeaderSize];
	memset(header, 0, kHeaderSize);

	uint32 num_colors =
	pwg_header_info.color_space == PwgHeaderInfo::SGRAY ? 1 : 3;
	uint32 bits_per_pixel = num_colors * kBitsPerColor;

	base::WriteBigEndian<uint32>(header + kHeaderCupsDuplex,
	pwg_header_info.duplex ? 1 : 0);
	base::WriteBigEndian<uint32>(header + kHeaderCupsHwResolutionHorizontal,
	pwg_header_info.dpi);
	base::WriteBigEndian<uint32>(header + kHeaderCupsHwResolutionVertical,
	pwg_header_info.dpi);
	base::WriteBigEndian<uint32>(header + kHeaderCupsTumble,
	pwg_header_info.tumble ? 1 : 0);
	base::WriteBigEndian<uint32>(header + kHeaderCupsWidth, image.size().width());
	base::WriteBigEndian<uint32>(header + kHeaderCupsHeight,
	image.size().height());
	base::WriteBigEndian<uint32>(header + kHeaderCupsBitsPerColor, kBitsPerColor);
	base::WriteBigEndian<uint32>(header + kHeaderCupsBitsPerPixel,
	bits_per_pixel);
	base::WriteBigEndian<uint32>(header + kHeaderCupsBytesPerLine,
	(bits_per_pixel * image.size().width() + 7) / 8);
	base::WriteBigEndian<uint32>(header + kHeaderCupsColorOrder, kColorOrder);
	base::WriteBigEndian<uint32>(header + kHeaderCupsColorSpace,
	pwg_header_info.color_space);
	base::WriteBigEndian<uint32>(header + kHeaderCupsNumColors, num_colors);
	base::WriteBigEndian<uint32>(header + kHeaderPwgCrossFeedTransform,
	pwg_header_info.flipx ? -1 : 1);
	base::WriteBigEndian<uint32>(header + kHeaderPwgFeedTransform,
	pwg_header_info.flipy ? -1 : 1);
	base::WriteBigEndian<uint32>(header + kHeaderPwgTotalPageCount,
	pwg_header_info.total_pages);
	output->append(header, kHeaderSize);
	}

	template <typename InputStruct, class RandomAccessIterator>
	void PwgEncoder::EncodeRow(RandomAccessIterator pos,
	RandomAccessIterator row_end,
	bool monochrome,
	std::string* output) const {
	// According to PWG-raster, a sequence of N identical pixels (up to 128)
	// can be encoded by a byte N-1, followed by the information on
	// that pixel. Any generic sequence of N pixels (up to 129) can be encoded
	// with (signed) byte 1-N, followed by the information on the N pixels.
	// Notice that for sequences of 1 pixel there is no difference between
	// the two encodings.

	// We encode every largest sequence of identical pixels together because it
	// usually saves the most space. Every other pixel should be encoded in the
	// smallest number of generic sequences.
	// NOTE: the algorithm is not optimal especially in case of monochrome.
	while (pos != row_end) {
	RandomAccessIterator it = pos + 1;
	RandomAccessIterator end = std::min(pos + kPwgMaxPackedPixels, row_end);

	// Counts how many identical pixels (up to 128).
	while (it != end && pos == it) {
	++it;
	}
	if (it != pos + 1) { // More than one pixel
	output->push_back(static_cast<char>((it - pos) - 1));
	if (monochrome)
	encodePixelToMonochrome<InputStruct>(&*pos, output);
	else
	encodePixelToRGB<InputStruct>(&*pos, output);
	pos = it;
	} else {
	// Finds how many pixels there are each different from the previous one.
	// IMPORTANT: even if sequences of different pixels can contain as many
	// as 129 pixels, we restrict to 128 because some decoders don't manage
	// it correctly. So iterating until it != end is correct.
	while (it != end && it != (it - 1)) {
	++it;
	}
	// Optimization: ignores the last pixel of the sequence if it is followed
	// by an identical pixel, as it is more convenient for it to be the start
	// of a new sequence of identical pixels. Notice that we don't compare
	// to end, but row_end.
	if (it != row_end && it == (it - 1)) {
	--it;
	}
	output->push_back(static_cast<char>(1 - (it - pos)));
	while (pos != it) {
	if (monochrome)
	encodePixelToMonochrome<InputStruct>(&*pos, output);
	else
	encodePixelToRGB<InputStruct>(&*pos, output);
	++pos;
	}
	}
	}
	}

	inline const uint8* PwgEncoder::GetRow(const BitmapImage& image,
	int row,
	bool flipy) const {
	return image.GetPixel(
	gfx::Point(0, flipy ? image.size().height() - 1 - row : row));
	}

	// Given a pointer to a struct Image, create a PWG of the image and
	// put the compressed image data in the string. Returns true on success.
	// The content of the string is undefined on failure.
	bool PwgEncoder::EncodePage(const BitmapImage& image,
	const PwgHeaderInfo& pwg_header_info,
	std::string* output) const {
	// pwg_header_info.color_space can only contain color spaces that are
	// supported, so no sanity check is needed.
	switch (image.colorspace()) {
	case BitmapImage::RGBA:
	return EncodePageWithColorspace<RGBA8>(image, pwg_header_info, output);

	case BitmapImage::BGRA:
	return EncodePageWithColorspace<BGRA8>(image, pwg_header_info, output);

	default:
	LOG(ERROR) << "Unsupported colorspace.";
	return false;
	}
	}

	template <typename InputStruct>
	bool PwgEncoder::EncodePageWithColorspace(const BitmapImage& image,
	const PwgHeaderInfo& pwg_header_info,
	std::string* output) const {
	bool monochrome = pwg_header_info.color_space == PwgHeaderInfo::SGRAY;
	EncodePageHeader(image, pwg_header_info, output);

	// Ensure no integer overflow.
	CHECK(image.size().width() < INT_MAX / image.channels());
	int row_size = image.size().width() * image.channels();

	int row_number = 0;
	while (row_number < image.size().height()) {
	const uint8* current_row =
	GetRow(image, row_number++, pwg_header_info.flipy);
	int num_identical_rows = 1;
	// We count how many times the current row is repeated.
	while (num_identical_rows < kPwgMaxPackedRows &&
	row_number < image.size().height() &&
	!memcmp(current_row,
	GetRow(image, row_number, pwg_header_info.flipy),
	row_size)) {
	num_identical_rows++;
	row_number++;
	}
	output->push_back(static_cast<char>(num_identical_rows - 1));

	// Both supported colorspaces have a 32-bit pixels information.
	// Converts the list of uint8 to uint32 as every pixels contains 4 bytes
	// of information and comparison of elements is easier. The actual
	// Management of the bytes of the pixel is done by pixel_encoder function
	// on the original array to avoid endian problems.
	const uint32* pos = reinterpret_cast<const uint32*>(current_row);
	const uint32* row_end = pos + image.size().width();
	if (!pwg_header_info.flipx) {
	EncodeRow<InputStruct>(pos, row_end, monochrome, output);
	} else {
	// We reverse the iterators.
	EncodeRow<InputStruct>(std::reverse_iterator<const uint32*>(row_end),
	std::reverse_iterator<const uint32*>(pos),
	monochrome,
	output);
	}
	}
	return true;
	}

	} // namespace cloud_print