1// Copyright 2015 PDFium 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// Original code copyright 2014 Foxit Software Inc. http://www.foxitsoftware.com
6
7#include "core/fxcodec/jbig2/JBig2_GrrdProc.h"
8
9#include <memory>
10
11#include "core/fxcodec/jbig2/JBig2_ArithDecoder.h"
12#include "core/fxcodec/jbig2/JBig2_BitStream.h"
13#include "core/fxcodec/jbig2/JBig2_Image.h"
14#include "third_party/base/ptr_util.h"
15
16std::unique_ptr<CJBig2_Image> CJBig2_GRRDProc::decode(
17    CJBig2_ArithDecoder* pArithDecoder,
18    JBig2ArithCtx* grContext) {
19  if (GRW == 0 || GRW > JBIG2_MAX_IMAGE_SIZE || GRH == 0 ||
20      GRH > JBIG2_MAX_IMAGE_SIZE) {
21    return pdfium::MakeUnique<CJBig2_Image>(GRW, GRH);
22  }
23
24  if (!GRTEMPLATE) {
25    if ((GRAT[0] == -1) && (GRAT[1] == -1) && (GRAT[2] == -1) &&
26        (GRAT[3] == -1) && (GRREFERENCEDX == 0) &&
27        (GRW == (uint32_t)GRREFERENCE->width())) {
28      return decode_Template0_opt(pArithDecoder, grContext);
29    }
30    return decode_Template0_unopt(pArithDecoder, grContext);
31  }
32
33  if ((GRREFERENCEDX == 0) && (GRW == (uint32_t)GRREFERENCE->width()))
34    return decode_Template1_opt(pArithDecoder, grContext);
35
36  return decode_Template1_unopt(pArithDecoder, grContext);
37}
38
39std::unique_ptr<CJBig2_Image> CJBig2_GRRDProc::decode_Template0_unopt(
40    CJBig2_ArithDecoder* pArithDecoder,
41    JBig2ArithCtx* grContext) {
42  int LTP = 0;
43  auto GRREG = pdfium::MakeUnique<CJBig2_Image>(GRW, GRH);
44  GRREG->fill(0);
45  for (uint32_t h = 0; h < GRH; h++) {
46    if (TPGRON) {
47      if (pArithDecoder->IsComplete())
48        return nullptr;
49
50      LTP = LTP ^ pArithDecoder->DECODE(&grContext[0x0010]);
51    }
52    uint32_t lines[5];
53    lines[0] = GRREG->getPixel(1, h - 1);
54    lines[0] |= GRREG->getPixel(0, h - 1) << 1;
55    lines[1] = 0;
56    lines[2] = GRREFERENCE->getPixel(-GRREFERENCEDX + 1, h - GRREFERENCEDY - 1);
57    lines[2] |= GRREFERENCE->getPixel(-GRREFERENCEDX, h - GRREFERENCEDY - 1)
58                << 1;
59    lines[3] = GRREFERENCE->getPixel(-GRREFERENCEDX + 1, h - GRREFERENCEDY);
60    lines[3] |= GRREFERENCE->getPixel(-GRREFERENCEDX, h - GRREFERENCEDY) << 1;
61    lines[3] |= GRREFERENCE->getPixel(-GRREFERENCEDX - 1, h - GRREFERENCEDY)
62                << 2;
63    lines[4] = GRREFERENCE->getPixel(-GRREFERENCEDX + 1, h - GRREFERENCEDY + 1);
64    lines[4] |= GRREFERENCE->getPixel(-GRREFERENCEDX, h - GRREFERENCEDY + 1)
65                << 1;
66    lines[4] |= GRREFERENCE->getPixel(-GRREFERENCEDX - 1, h - GRREFERENCEDY + 1)
67                << 2;
68    if (!LTP) {
69      for (uint32_t w = 0; w < GRW; w++) {
70        uint32_t CONTEXT =
71            decode_Template0_unopt_CalculateContext(*GRREG, lines, w, h);
72        if (pArithDecoder->IsComplete())
73          return nullptr;
74
75        int bVal = pArithDecoder->DECODE(&grContext[CONTEXT]);
76        decode_Template0_unopt_SetPixel(GRREG.get(), lines, w, h, bVal);
77      }
78    } else {
79      for (uint32_t w = 0; w < GRW; w++) {
80        int bVal = GRREFERENCE->getPixel(w, h);
81        if (!(TPGRON && (bVal == GRREFERENCE->getPixel(w - 1, h - 1)) &&
82              (bVal == GRREFERENCE->getPixel(w, h - 1)) &&
83              (bVal == GRREFERENCE->getPixel(w + 1, h - 1)) &&
84              (bVal == GRREFERENCE->getPixel(w - 1, h)) &&
85              (bVal == GRREFERENCE->getPixel(w + 1, h)) &&
86              (bVal == GRREFERENCE->getPixel(w - 1, h + 1)) &&
87              (bVal == GRREFERENCE->getPixel(w, h + 1)) &&
88              (bVal == GRREFERENCE->getPixel(w + 1, h + 1)))) {
89          uint32_t CONTEXT =
90              decode_Template0_unopt_CalculateContext(*GRREG, lines, w, h);
91          if (pArithDecoder->IsComplete())
92            return nullptr;
93
94          bVal = pArithDecoder->DECODE(&grContext[CONTEXT]);
95        }
96        decode_Template0_unopt_SetPixel(GRREG.get(), lines, w, h, bVal);
97      }
98    }
99  }
100  return GRREG;
101}
102
103uint32_t CJBig2_GRRDProc::decode_Template0_unopt_CalculateContext(
104    const CJBig2_Image& GRREG,
105    const uint32_t* lines,
106    uint32_t w,
107    uint32_t h) const {
108  uint32_t CONTEXT = lines[4];
109  CONTEXT |= lines[3] << 3;
110  CONTEXT |= lines[2] << 6;
111  CONTEXT |= GRREFERENCE->getPixel(w - GRREFERENCEDX + GRAT[2],
112                                   h - GRREFERENCEDY + GRAT[3])
113             << 8;
114  CONTEXT |= lines[1] << 9;
115  CONTEXT |= lines[0] << 10;
116  CONTEXT |= GRREG.getPixel(w + GRAT[0], h + GRAT[1]) << 12;
117  return CONTEXT;
118}
119
120void CJBig2_GRRDProc::decode_Template0_unopt_SetPixel(CJBig2_Image* GRREG,
121                                                      uint32_t* lines,
122                                                      uint32_t w,
123                                                      uint32_t h,
124                                                      int bVal) {
125  GRREG->setPixel(w, h, bVal);
126  lines[0] = ((lines[0] << 1) | GRREG->getPixel(w + 2, h - 1)) & 0x03;
127  lines[1] = ((lines[1] << 1) | bVal) & 0x01;
128  lines[2] = ((lines[2] << 1) | GRREFERENCE->getPixel(w - GRREFERENCEDX + 2,
129                                                      h - GRREFERENCEDY - 1)) &
130             0x03;
131  lines[3] = ((lines[3] << 1) |
132              GRREFERENCE->getPixel(w - GRREFERENCEDX + 2, h - GRREFERENCEDY)) &
133             0x07;
134  lines[4] = ((lines[4] << 1) | GRREFERENCE->getPixel(w - GRREFERENCEDX + 2,
135                                                      h - GRREFERENCEDY + 1)) &
136             0x07;
137}
138
139std::unique_ptr<CJBig2_Image> CJBig2_GRRDProc::decode_Template0_opt(
140    CJBig2_ArithDecoder* pArithDecoder,
141    JBig2ArithCtx* grContext) {
142  if (!GRREFERENCE->data())
143    return nullptr;
144
145  int32_t iGRW = static_cast<int32_t>(GRW);
146  int32_t iGRH = static_cast<int32_t>(GRH);
147  auto GRREG = pdfium::MakeUnique<CJBig2_Image>(iGRW, iGRH);
148  if (!GRREG->data())
149    return nullptr;
150
151  int LTP = 0;
152  uint8_t* pLine = GRREG->data();
153  uint8_t* pLineR = GRREFERENCE->data();
154  intptr_t nStride = GRREG->stride();
155  intptr_t nStrideR = GRREFERENCE->stride();
156  int32_t GRWR = GRREFERENCE->width();
157  int32_t GRHR = GRREFERENCE->height();
158  if (GRREFERENCEDY < -GRHR + 1 || GRREFERENCEDY > GRHR - 1)
159    GRREFERENCEDY = 0;
160  intptr_t nOffset = -GRREFERENCEDY * nStrideR;
161  for (int32_t h = 0; h < iGRH; h++) {
162    if (TPGRON) {
163      if (pArithDecoder->IsComplete())
164        return nullptr;
165
166      LTP = LTP ^ pArithDecoder->DECODE(&grContext[0x0010]);
167    }
168    uint32_t line1 = (h > 0) ? pLine[-nStride] << 4 : 0;
169    int32_t reference_h = h - GRREFERENCEDY;
170    bool line1_r_ok = (reference_h > 0 && reference_h < GRHR + 1);
171    bool line2_r_ok = (reference_h > -1 && reference_h < GRHR);
172    bool line3_r_ok = (reference_h > -2 && reference_h < GRHR - 1);
173    uint32_t line1_r = line1_r_ok ? pLineR[nOffset - nStrideR] : 0;
174    uint32_t line2_r = line2_r_ok ? pLineR[nOffset] : 0;
175    uint32_t line3_r = line3_r_ok ? pLineR[nOffset + nStrideR] : 0;
176    if (!LTP) {
177      uint32_t CONTEXT = (line1 & 0x1c00) | (line1_r & 0x01c0) |
178                         ((line2_r >> 3) & 0x0038) | ((line3_r >> 6) & 0x0007);
179      for (int32_t w = 0; w < iGRW; w += 8) {
180        int32_t nBits = iGRW - w > 8 ? 8 : iGRW - w;
181        if (h > 0) {
182          line1 = (line1 << 8) |
183                  (w + 8 < iGRW ? pLine[-nStride + (w >> 3) + 1] << 4 : 0);
184        }
185        if (h > GRHR + GRREFERENCEDY + 1) {
186          line1_r = 0;
187          line2_r = 0;
188          line3_r = 0;
189        } else {
190          if (line1_r_ok) {
191            line1_r =
192                (line1_r << 8) |
193                (w + 8 < GRWR ? pLineR[nOffset - nStrideR + (w >> 3) + 1] : 0);
194          }
195          if (line2_r_ok) {
196            line2_r = (line2_r << 8) |
197                      (w + 8 < GRWR ? pLineR[nOffset + (w >> 3) + 1] : 0);
198          }
199          if (line3_r_ok) {
200            line3_r =
201                (line3_r << 8) |
202                (w + 8 < GRWR ? pLineR[nOffset + nStrideR + (w >> 3) + 1] : 0);
203          } else {
204            line3_r = 0;
205          }
206        }
207        uint8_t cVal = 0;
208        for (int32_t k = 0; k < nBits; k++) {
209          if (pArithDecoder->IsComplete())
210            return nullptr;
211
212          int bVal = pArithDecoder->DECODE(&grContext[CONTEXT]);
213          cVal |= bVal << (7 - k);
214          CONTEXT = ((CONTEXT & 0x0cdb) << 1) | (bVal << 9) |
215                    ((line1 >> (7 - k)) & 0x0400) |
216                    ((line1_r >> (7 - k)) & 0x0040) |
217                    ((line2_r >> (10 - k)) & 0x0008) |
218                    ((line3_r >> (13 - k)) & 0x0001);
219        }
220        pLine[w >> 3] = cVal;
221      }
222    } else {
223      uint32_t CONTEXT = (line1 & 0x1c00) | (line1_r & 0x01c0) |
224                         ((line2_r >> 3) & 0x0038) | ((line3_r >> 6) & 0x0007);
225      for (int32_t w = 0; w < iGRW; w += 8) {
226        int32_t nBits = iGRW - w > 8 ? 8 : iGRW - w;
227        if (h > 0) {
228          line1 = (line1 << 8) |
229                  (w + 8 < iGRW ? pLine[-nStride + (w >> 3) + 1] << 4 : 0);
230        }
231        if (line1_r_ok) {
232          line1_r =
233              (line1_r << 8) |
234              (w + 8 < GRWR ? pLineR[nOffset - nStrideR + (w >> 3) + 1] : 0);
235        }
236        if (line2_r_ok) {
237          line2_r = (line2_r << 8) |
238                    (w + 8 < GRWR ? pLineR[nOffset + (w >> 3) + 1] : 0);
239        }
240        if (line3_r_ok) {
241          line3_r =
242              (line3_r << 8) |
243              (w + 8 < GRWR ? pLineR[nOffset + nStrideR + (w >> 3) + 1] : 0);
244        } else {
245          line3_r = 0;
246        }
247        uint8_t cVal = 0;
248        for (int32_t k = 0; k < nBits; k++) {
249          int bVal = GRREFERENCE->getPixel(w + k, h);
250          if (!(TPGRON && (bVal == GRREFERENCE->getPixel(w + k - 1, h - 1)) &&
251                (bVal == GRREFERENCE->getPixel(w + k, h - 1)) &&
252                (bVal == GRREFERENCE->getPixel(w + k + 1, h - 1)) &&
253                (bVal == GRREFERENCE->getPixel(w + k - 1, h)) &&
254                (bVal == GRREFERENCE->getPixel(w + k + 1, h)) &&
255                (bVal == GRREFERENCE->getPixel(w + k - 1, h + 1)) &&
256                (bVal == GRREFERENCE->getPixel(w + k, h + 1)) &&
257                (bVal == GRREFERENCE->getPixel(w + k + 1, h + 1)))) {
258            if (pArithDecoder->IsComplete())
259              return nullptr;
260
261            bVal = pArithDecoder->DECODE(&grContext[CONTEXT]);
262          }
263          cVal |= bVal << (7 - k);
264          CONTEXT = ((CONTEXT & 0x0cdb) << 1) | (bVal << 9) |
265                    ((line1 >> (7 - k)) & 0x0400) |
266                    ((line1_r >> (7 - k)) & 0x0040) |
267                    ((line2_r >> (10 - k)) & 0x0008) |
268                    ((line3_r >> (13 - k)) & 0x0001);
269        }
270        pLine[w >> 3] = cVal;
271      }
272    }
273    pLine += nStride;
274    if (h < GRHR + GRREFERENCEDY)
275      pLineR += nStrideR;
276  }
277  return GRREG;
278}
279
280std::unique_ptr<CJBig2_Image> CJBig2_GRRDProc::decode_Template1_unopt(
281    CJBig2_ArithDecoder* pArithDecoder,
282    JBig2ArithCtx* grContext) {
283  int LTP = 0;
284  auto GRREG = pdfium::MakeUnique<CJBig2_Image>(GRW, GRH);
285  GRREG->fill(0);
286  for (uint32_t h = 0; h < GRH; h++) {
287    if (TPGRON) {
288      if (pArithDecoder->IsComplete())
289        return nullptr;
290
291      LTP = LTP ^ pArithDecoder->DECODE(&grContext[0x0008]);
292    }
293    if (!LTP) {
294      uint32_t line1 = GRREG->getPixel(1, h - 1);
295      line1 |= GRREG->getPixel(0, h - 1) << 1;
296      line1 |= GRREG->getPixel(-1, h - 1) << 2;
297      uint32_t line2 = 0;
298      uint32_t line3 =
299          GRREFERENCE->getPixel(-GRREFERENCEDX, h - GRREFERENCEDY - 1);
300      uint32_t line4 =
301          GRREFERENCE->getPixel(-GRREFERENCEDX + 1, h - GRREFERENCEDY);
302      line4 |= GRREFERENCE->getPixel(-GRREFERENCEDX, h - GRREFERENCEDY) << 1;
303      line4 |= GRREFERENCE->getPixel(-GRREFERENCEDX - 1, h - GRREFERENCEDY)
304               << 2;
305      uint32_t line5 =
306          GRREFERENCE->getPixel(-GRREFERENCEDX + 1, h - GRREFERENCEDY + 1);
307      line5 |= GRREFERENCE->getPixel(-GRREFERENCEDX, h - GRREFERENCEDY + 1)
308               << 1;
309      for (uint32_t w = 0; w < GRW; w++) {
310        uint32_t CONTEXT = line5;
311        CONTEXT |= line4 << 2;
312        CONTEXT |= line3 << 5;
313        CONTEXT |= line2 << 6;
314        CONTEXT |= line1 << 7;
315        if (pArithDecoder->IsComplete())
316          return nullptr;
317
318        int bVal = pArithDecoder->DECODE(&grContext[CONTEXT]);
319        GRREG->setPixel(w, h, bVal);
320        line1 = ((line1 << 1) | GRREG->getPixel(w + 2, h - 1)) & 0x07;
321        line2 = ((line2 << 1) | bVal) & 0x01;
322        line3 = ((line3 << 1) |
323                 GRREFERENCE->getPixel(w - GRREFERENCEDX + 1,
324                                       h - GRREFERENCEDY - 1)) &
325                0x01;
326        line4 =
327            ((line4 << 1) |
328             GRREFERENCE->getPixel(w - GRREFERENCEDX + 2, h - GRREFERENCEDY)) &
329            0x07;
330        line5 = ((line5 << 1) |
331                 GRREFERENCE->getPixel(w - GRREFERENCEDX + 2,
332                                       h - GRREFERENCEDY + 1)) &
333                0x03;
334      }
335    } else {
336      uint32_t line1 = GRREG->getPixel(1, h - 1);
337      line1 |= GRREG->getPixel(0, h - 1) << 1;
338      line1 |= GRREG->getPixel(-1, h - 1) << 2;
339      uint32_t line2 = 0;
340      uint32_t line3 =
341          GRREFERENCE->getPixel(-GRREFERENCEDX, h - GRREFERENCEDY - 1);
342      uint32_t line4 =
343          GRREFERENCE->getPixel(-GRREFERENCEDX + 1, h - GRREFERENCEDY);
344      line4 |= GRREFERENCE->getPixel(-GRREFERENCEDX, h - GRREFERENCEDY) << 1;
345      line4 |= GRREFERENCE->getPixel(-GRREFERENCEDX - 1, h - GRREFERENCEDY)
346               << 2;
347      uint32_t line5 =
348          GRREFERENCE->getPixel(-GRREFERENCEDX + 1, h - GRREFERENCEDY + 1);
349      line5 |= GRREFERENCE->getPixel(-GRREFERENCEDX, h - GRREFERENCEDY + 1)
350               << 1;
351      for (uint32_t w = 0; w < GRW; w++) {
352        int bVal = GRREFERENCE->getPixel(w, h);
353        if (!(TPGRON && (bVal == GRREFERENCE->getPixel(w - 1, h - 1)) &&
354              (bVal == GRREFERENCE->getPixel(w, h - 1)) &&
355              (bVal == GRREFERENCE->getPixel(w + 1, h - 1)) &&
356              (bVal == GRREFERENCE->getPixel(w - 1, h)) &&
357              (bVal == GRREFERENCE->getPixel(w + 1, h)) &&
358              (bVal == GRREFERENCE->getPixel(w - 1, h + 1)) &&
359              (bVal == GRREFERENCE->getPixel(w, h + 1)) &&
360              (bVal == GRREFERENCE->getPixel(w + 1, h + 1)))) {
361          uint32_t CONTEXT = line5;
362          CONTEXT |= line4 << 2;
363          CONTEXT |= line3 << 5;
364          CONTEXT |= line2 << 6;
365          CONTEXT |= line1 << 7;
366          if (pArithDecoder->IsComplete())
367            return nullptr;
368
369          bVal = pArithDecoder->DECODE(&grContext[CONTEXT]);
370        }
371        GRREG->setPixel(w, h, bVal);
372        line1 = ((line1 << 1) | GRREG->getPixel(w + 2, h - 1)) & 0x07;
373        line2 = ((line2 << 1) | bVal) & 0x01;
374        line3 = ((line3 << 1) |
375                 GRREFERENCE->getPixel(w - GRREFERENCEDX + 1,
376                                       h - GRREFERENCEDY - 1)) &
377                0x01;
378        line4 =
379            ((line4 << 1) |
380             GRREFERENCE->getPixel(w - GRREFERENCEDX + 2, h - GRREFERENCEDY)) &
381            0x07;
382        line5 = ((line5 << 1) |
383                 GRREFERENCE->getPixel(w - GRREFERENCEDX + 2,
384                                       h - GRREFERENCEDY + 1)) &
385                0x03;
386      }
387    }
388  }
389  return GRREG;
390}
391
392std::unique_ptr<CJBig2_Image> CJBig2_GRRDProc::decode_Template1_opt(
393    CJBig2_ArithDecoder* pArithDecoder,
394    JBig2ArithCtx* grContext) {
395  if (!GRREFERENCE->data())
396    return nullptr;
397
398  int32_t iGRW = static_cast<int32_t>(GRW);
399  int32_t iGRH = static_cast<int32_t>(GRH);
400  auto GRREG = pdfium::MakeUnique<CJBig2_Image>(iGRW, iGRH);
401  if (!GRREG->data())
402    return nullptr;
403
404  int LTP = 0;
405  uint8_t* pLine = GRREG->data();
406  uint8_t* pLineR = GRREFERENCE->data();
407  intptr_t nStride = GRREG->stride();
408  intptr_t nStrideR = GRREFERENCE->stride();
409  int32_t GRWR = GRREFERENCE->width();
410  int32_t GRHR = GRREFERENCE->height();
411  if (GRREFERENCEDY < -GRHR + 1 || GRREFERENCEDY > GRHR - 1) {
412    GRREFERENCEDY = 0;
413  }
414  intptr_t nOffset = -GRREFERENCEDY * nStrideR;
415  for (int32_t h = 0; h < iGRH; h++) {
416    if (TPGRON) {
417      if (pArithDecoder->IsComplete())
418        return nullptr;
419
420      LTP = LTP ^ pArithDecoder->DECODE(&grContext[0x0008]);
421    }
422    uint32_t line1 = (h > 0) ? pLine[-nStride] << 1 : 0;
423    int32_t reference_h = h - GRREFERENCEDY;
424    bool line1_r_ok = (reference_h > 0 && reference_h < GRHR + 1);
425    bool line2_r_ok = (reference_h > -1 && reference_h < GRHR);
426    bool line3_r_ok = (reference_h > -2 && reference_h < GRHR - 1);
427    uint32_t line1_r = line1_r_ok ? pLineR[nOffset - nStrideR] : 0;
428    uint32_t line2_r = line2_r_ok ? pLineR[nOffset] : 0;
429    uint32_t line3_r = line3_r_ok ? pLineR[nOffset + nStrideR] : 0;
430    if (!LTP) {
431      uint32_t CONTEXT = (line1 & 0x0380) | ((line1_r >> 2) & 0x0020) |
432                         ((line2_r >> 4) & 0x001c) | ((line3_r >> 6) & 0x0003);
433      for (int32_t w = 0; w < iGRW; w += 8) {
434        int32_t nBits = iGRW - w > 8 ? 8 : iGRW - w;
435        if (h > 0)
436          line1 = (line1 << 8) |
437                  (w + 8 < iGRW ? pLine[-nStride + (w >> 3) + 1] << 1 : 0);
438        if (line1_r_ok)
439          line1_r =
440              (line1_r << 8) |
441              (w + 8 < GRWR ? pLineR[nOffset - nStrideR + (w >> 3) + 1] : 0);
442        if (line2_r_ok)
443          line2_r = (line2_r << 8) |
444                    (w + 8 < GRWR ? pLineR[nOffset + (w >> 3) + 1] : 0);
445        if (line3_r_ok) {
446          line3_r =
447              (line3_r << 8) |
448              (w + 8 < GRWR ? pLineR[nOffset + nStrideR + (w >> 3) + 1] : 0);
449        } else {
450          line3_r = 0;
451        }
452        uint8_t cVal = 0;
453        for (int32_t k = 0; k < nBits; k++) {
454          int bVal = pArithDecoder->DECODE(&grContext[CONTEXT]);
455          cVal |= bVal << (7 - k);
456          CONTEXT = ((CONTEXT & 0x018d) << 1) | (bVal << 6) |
457                    ((line1 >> (7 - k)) & 0x0080) |
458                    ((line1_r >> (9 - k)) & 0x0020) |
459                    ((line2_r >> (11 - k)) & 0x0004) |
460                    ((line3_r >> (13 - k)) & 0x0001);
461        }
462        pLine[w >> 3] = cVal;
463      }
464    } else {
465      uint32_t CONTEXT = (line1 & 0x0380) | ((line1_r >> 2) & 0x0020) |
466                         ((line2_r >> 4) & 0x001c) | ((line3_r >> 6) & 0x0003);
467      for (int32_t w = 0; w < iGRW; w += 8) {
468        int32_t nBits = iGRW - w > 8 ? 8 : iGRW - w;
469        if (h > 0)
470          line1 = (line1 << 8) |
471                  (w + 8 < iGRW ? pLine[-nStride + (w >> 3) + 1] << 1 : 0);
472        if (line1_r_ok)
473          line1_r =
474              (line1_r << 8) |
475              (w + 8 < GRWR ? pLineR[nOffset - nStrideR + (w >> 3) + 1] : 0);
476        if (line2_r_ok)
477          line2_r = (line2_r << 8) |
478                    (w + 8 < GRWR ? pLineR[nOffset + (w >> 3) + 1] : 0);
479        if (line3_r_ok) {
480          line3_r =
481              (line3_r << 8) |
482              (w + 8 < GRWR ? pLineR[nOffset + nStrideR + (w >> 3) + 1] : 0);
483        } else {
484          line3_r = 0;
485        }
486        uint8_t cVal = 0;
487        for (int32_t k = 0; k < nBits; k++) {
488          int bVal = GRREFERENCE->getPixel(w + k, h);
489          if (!(TPGRON && (bVal == GRREFERENCE->getPixel(w + k - 1, h - 1)) &&
490                (bVal == GRREFERENCE->getPixel(w + k, h - 1)) &&
491                (bVal == GRREFERENCE->getPixel(w + k + 1, h - 1)) &&
492                (bVal == GRREFERENCE->getPixel(w + k - 1, h)) &&
493                (bVal == GRREFERENCE->getPixel(w + k + 1, h)) &&
494                (bVal == GRREFERENCE->getPixel(w + k - 1, h + 1)) &&
495                (bVal == GRREFERENCE->getPixel(w + k, h + 1)) &&
496                (bVal == GRREFERENCE->getPixel(w + k + 1, h + 1)))) {
497            if (pArithDecoder->IsComplete())
498              return nullptr;
499
500            bVal = pArithDecoder->DECODE(&grContext[CONTEXT]);
501          }
502          cVal |= bVal << (7 - k);
503          CONTEXT = ((CONTEXT & 0x018d) << 1) | (bVal << 6) |
504                    ((line1 >> (7 - k)) & 0x0080) |
505                    ((line1_r >> (9 - k)) & 0x0020) |
506                    ((line2_r >> (11 - k)) & 0x0004) |
507                    ((line3_r >> (13 - k)) & 0x0001);
508        }
509        pLine[w >> 3] = cVal;
510      }
511    }
512    pLine += nStride;
513    if (h < GRHR + GRREFERENCEDY)
514      pLineR += nStrideR;
515  }
516  return GRREG;
517}
518