1 // Copyright 2013 The Chromium Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
4
5 #include "chrome/utility/cloud_print/pwg_encoder.h"
6
7 #include <algorithm>
8
9 #include "base/big_endian.h"
10 #include "base/logging.h"
11 #include "base/memory/scoped_ptr.h"
12 #include "chrome/utility/cloud_print/bitmap_image.h"
13
14 namespace cloud_print {
15
16 namespace {
17
18 const uint32 kBitsPerColor = 8;
19 const uint32 kColorOrder = 0; // chunky.
20
21 // Coefficients used to convert from RGB to monochrome.
22 const uint32 kRedCoefficient = 2125;
23 const uint32 kGreenCoefficient = 7154;
24 const uint32 kBlueCoefficient = 721;
25 const uint32 kColorCoefficientDenominator = 10000;
26
27 const char* kPwgKeyword = "RaS2";
28
29 const uint32 kHeaderSize = 1796;
30 const uint32 kHeaderCupsDuplex = 272;
31 const uint32 kHeaderCupsHwResolutionHorizontal = 276;
32 const uint32 kHeaderCupsHwResolutionVertical = 280;
33 const uint32 kHeaderCupsTumble = 368;
34 const uint32 kHeaderCupsWidth = 372;
35 const uint32 kHeaderCupsHeight = 376;
36 const uint32 kHeaderCupsBitsPerColor = 384;
37 const uint32 kHeaderCupsBitsPerPixel = 388;
38 const uint32 kHeaderCupsBytesPerLine = 392;
39 const uint32 kHeaderCupsColorOrder = 396;
40 const uint32 kHeaderCupsColorSpace = 400;
41 const uint32 kHeaderCupsNumColors = 420;
42 const uint32 kHeaderPwgTotalPageCount = 452;
43 const uint32 kHeaderPwgCrossFeedTransform = 456;
44 const uint32 kHeaderPwgFeedTransform = 460;
45
46 const int kPwgMaxPackedRows = 256;
47
48 const int kPwgMaxPackedPixels = 128;
49
50 struct RGBA8 {
51 uint8 red;
52 uint8 green;
53 uint8 blue;
54 uint8 alpha;
55 };
56
57 struct BGRA8 {
58 uint8 blue;
59 uint8 green;
60 uint8 red;
61 uint8 alpha;
62 };
63
64 template <class InputStruct>
encodePixelToRGB(const void * pixel,std::string * output)65 inline void encodePixelToRGB(const void* pixel, std::string* output) {
66 const InputStruct* i = reinterpret_cast<const InputStruct*>(pixel);
67 output->push_back(static_cast<char>(i->red));
68 output->push_back(static_cast<char>(i->green));
69 output->push_back(static_cast<char>(i->blue));
70 }
71
72 template <class InputStruct>
encodePixelToMonochrome(const void * pixel,std::string * output)73 inline void encodePixelToMonochrome(const void* pixel, std::string* output) {
74 const InputStruct* i = reinterpret_cast<const InputStruct*>(pixel);
75 output->push_back(static_cast<char>((i->red * kRedCoefficient +
76 i->green * kGreenCoefficient +
77 i->blue * kBlueCoefficient) /
78 kColorCoefficientDenominator));
79 }
80
81 } // namespace
82
PwgEncoder()83 PwgEncoder::PwgEncoder() {}
84
EncodeDocumentHeader(std::string * output) const85 void PwgEncoder::EncodeDocumentHeader(std::string* output) const {
86 output->clear();
87 output->append(kPwgKeyword, 4);
88 }
89
EncodePageHeader(const BitmapImage & image,const PwgHeaderInfo & pwg_header_info,std::string * output) const90 void PwgEncoder::EncodePageHeader(const BitmapImage& image,
91 const PwgHeaderInfo& pwg_header_info,
92 std::string* output) const {
93 char header[kHeaderSize];
94 memset(header, 0, kHeaderSize);
95
96 uint32 num_colors =
97 pwg_header_info.color_space == PwgHeaderInfo::SGRAY ? 1 : 3;
98 uint32 bits_per_pixel = num_colors * kBitsPerColor;
99
100 base::WriteBigEndian<uint32>(header + kHeaderCupsDuplex,
101 pwg_header_info.duplex ? 1 : 0);
102 base::WriteBigEndian<uint32>(header + kHeaderCupsHwResolutionHorizontal,
103 pwg_header_info.dpi);
104 base::WriteBigEndian<uint32>(header + kHeaderCupsHwResolutionVertical,
105 pwg_header_info.dpi);
106 base::WriteBigEndian<uint32>(header + kHeaderCupsTumble,
107 pwg_header_info.tumble ? 1 : 0);
108 base::WriteBigEndian<uint32>(header + kHeaderCupsWidth, image.size().width());
109 base::WriteBigEndian<uint32>(header + kHeaderCupsHeight,
110 image.size().height());
111 base::WriteBigEndian<uint32>(header + kHeaderCupsBitsPerColor, kBitsPerColor);
112 base::WriteBigEndian<uint32>(header + kHeaderCupsBitsPerPixel,
113 bits_per_pixel);
114 base::WriteBigEndian<uint32>(header + kHeaderCupsBytesPerLine,
115 (bits_per_pixel * image.size().width() + 7) / 8);
116 base::WriteBigEndian<uint32>(header + kHeaderCupsColorOrder, kColorOrder);
117 base::WriteBigEndian<uint32>(header + kHeaderCupsColorSpace,
118 pwg_header_info.color_space);
119 base::WriteBigEndian<uint32>(header + kHeaderCupsNumColors, num_colors);
120 base::WriteBigEndian<uint32>(header + kHeaderPwgCrossFeedTransform,
121 pwg_header_info.flipx ? -1 : 1);
122 base::WriteBigEndian<uint32>(header + kHeaderPwgFeedTransform,
123 pwg_header_info.flipy ? -1 : 1);
124 base::WriteBigEndian<uint32>(header + kHeaderPwgTotalPageCount,
125 pwg_header_info.total_pages);
126 output->append(header, kHeaderSize);
127 }
128
129 template <typename InputStruct, class RandomAccessIterator>
EncodeRow(RandomAccessIterator pos,RandomAccessIterator row_end,bool monochrome,std::string * output) const130 void PwgEncoder::EncodeRow(RandomAccessIterator pos,
131 RandomAccessIterator row_end,
132 bool monochrome,
133 std::string* output) const {
134 // According to PWG-raster, a sequence of N identical pixels (up to 128)
135 // can be encoded by a byte N-1, followed by the information on
136 // that pixel. Any generic sequence of N pixels (up to 129) can be encoded
137 // with (signed) byte 1-N, followed by the information on the N pixels.
138 // Notice that for sequences of 1 pixel there is no difference between
139 // the two encodings.
140
141 // We encode every largest sequence of identical pixels together because it
142 // usually saves the most space. Every other pixel should be encoded in the
143 // smallest number of generic sequences.
144 // NOTE: the algorithm is not optimal especially in case of monochrome.
145 while (pos != row_end) {
146 RandomAccessIterator it = pos + 1;
147 RandomAccessIterator end = std::min(pos + kPwgMaxPackedPixels, row_end);
148
149 // Counts how many identical pixels (up to 128).
150 while (it != end && *pos == *it) {
151 ++it;
152 }
153 if (it != pos + 1) { // More than one pixel
154 output->push_back(static_cast<char>((it - pos) - 1));
155 if (monochrome)
156 encodePixelToMonochrome<InputStruct>(&*pos, output);
157 else
158 encodePixelToRGB<InputStruct>(&*pos, output);
159 pos = it;
160 } else {
161 // Finds how many pixels there are each different from the previous one.
162 // IMPORTANT: even if sequences of different pixels can contain as many
163 // as 129 pixels, we restrict to 128 because some decoders don't manage
164 // it correctly. So iterating until it != end is correct.
165 while (it != end && *it != *(it - 1)) {
166 ++it;
167 }
168 // Optimization: ignores the last pixel of the sequence if it is followed
169 // by an identical pixel, as it is more convenient for it to be the start
170 // of a new sequence of identical pixels. Notice that we don't compare
171 // to end, but row_end.
172 if (it != row_end && *it == *(it - 1)) {
173 --it;
174 }
175 output->push_back(static_cast<char>(1 - (it - pos)));
176 while (pos != it) {
177 if (monochrome)
178 encodePixelToMonochrome<InputStruct>(&*pos, output);
179 else
180 encodePixelToRGB<InputStruct>(&*pos, output);
181 ++pos;
182 }
183 }
184 }
185 }
186
GetRow(const BitmapImage & image,int row,bool flipy) const187 inline const uint8* PwgEncoder::GetRow(const BitmapImage& image,
188 int row,
189 bool flipy) const {
190 return image.GetPixel(
191 gfx::Point(0, flipy ? image.size().height() - 1 - row : row));
192 }
193
194 // Given a pointer to a struct Image, create a PWG of the image and
195 // put the compressed image data in the string. Returns true on success.
196 // The content of the string is undefined on failure.
EncodePage(const BitmapImage & image,const PwgHeaderInfo & pwg_header_info,std::string * output) const197 bool PwgEncoder::EncodePage(const BitmapImage& image,
198 const PwgHeaderInfo& pwg_header_info,
199 std::string* output) const {
200 // pwg_header_info.color_space can only contain color spaces that are
201 // supported, so no sanity check is needed.
202 switch (image.colorspace()) {
203 case BitmapImage::RGBA:
204 return EncodePageWithColorspace<RGBA8>(image, pwg_header_info, output);
205
206 case BitmapImage::BGRA:
207 return EncodePageWithColorspace<BGRA8>(image, pwg_header_info, output);
208
209 default:
210 LOG(ERROR) << "Unsupported colorspace.";
211 return false;
212 }
213 }
214
215 template <typename InputStruct>
EncodePageWithColorspace(const BitmapImage & image,const PwgHeaderInfo & pwg_header_info,std::string * output) const216 bool PwgEncoder::EncodePageWithColorspace(const BitmapImage& image,
217 const PwgHeaderInfo& pwg_header_info,
218 std::string* output) const {
219 bool monochrome = pwg_header_info.color_space == PwgHeaderInfo::SGRAY;
220 EncodePageHeader(image, pwg_header_info, output);
221
222 // Ensure no integer overflow.
223 CHECK(image.size().width() < INT_MAX / image.channels());
224 int row_size = image.size().width() * image.channels();
225
226 int row_number = 0;
227 while (row_number < image.size().height()) {
228 const uint8* current_row =
229 GetRow(image, row_number++, pwg_header_info.flipy);
230 int num_identical_rows = 1;
231 // We count how many times the current row is repeated.
232 while (num_identical_rows < kPwgMaxPackedRows &&
233 row_number < image.size().height() &&
234 !memcmp(current_row,
235 GetRow(image, row_number, pwg_header_info.flipy),
236 row_size)) {
237 num_identical_rows++;
238 row_number++;
239 }
240 output->push_back(static_cast<char>(num_identical_rows - 1));
241
242 // Both supported colorspaces have a 32-bit pixels information.
243 // Converts the list of uint8 to uint32 as every pixels contains 4 bytes
244 // of information and comparison of elements is easier. The actual
245 // Management of the bytes of the pixel is done by pixel_encoder function
246 // on the original array to avoid endian problems.
247 const uint32* pos = reinterpret_cast<const uint32*>(current_row);
248 const uint32* row_end = pos + image.size().width();
249 if (!pwg_header_info.flipx) {
250 EncodeRow<InputStruct>(pos, row_end, monochrome, output);
251 } else {
252 // We reverse the iterators.
253 EncodeRow<InputStruct>(std::reverse_iterator<const uint32*>(row_end),
254 std::reverse_iterator<const uint32*>(pos),
255 monochrome,
256 output);
257 }
258 }
259 return true;
260 }
261
262 } // namespace cloud_print
263