/// <summary> /// MCU decoding for DC successive approximation refinement scan. /// Note: we assume such scans can be multi-component, although the spec /// is not very clear on the point. /// </summary> private bool decode_mcu_DC_refine(JBLOCK[] MCU_data) { /* Process restart marker if needed; may have to suspend */ if (m_cinfo.m_restart_interval != 0) { if (m_restarts_to_go == 0) { if (!process_restart()) { return(false); } } } /* Not worth the cycles to check insufficient_data here, * since we will not change the data anyway if we read zeroes. */ /* Load up working state */ int get_buffer; int bits_left; bitread_working_state br_state = new bitread_working_state(); BITREAD_LOAD_STATE(m_bitstate, out get_buffer, out bits_left, ref br_state); /* Outer loop handles each block in the MCU */ for (int blkn = 0; blkn < m_cinfo.m_blocks_in_MCU; blkn++) { /* Encoded data is simply the next bit of the two's-complement DC value */ if (!CHECK_BIT_BUFFER(ref br_state, 1, ref get_buffer, ref bits_left)) { return(false); } if (GET_BITS(1, get_buffer, ref bits_left) != 0) { /* 1 in the bit position being coded */ MCU_data[blkn][0] |= (short)(1 << m_cinfo.m_Al); } /* Note: since we use |=, repeating the assignment later is safe */ } /* Completed MCU, so update state */ BITREAD_SAVE_STATE(ref m_bitstate, get_buffer, bits_left); /* Account for restart interval (no-op if not using restarts) */ m_restarts_to_go--; return(true); }
/* * These methods provide the in-line portion of bit fetching. * Use CHECK_BIT_BUFFER to ensure there are N bits in get_buffer * before using GET_BITS, PEEK_BITS, or DROP_BITS. * The variables get_buffer and bits_left are assumed to be locals, * but the state struct might not be (jpeg_huff_decode needs this). * CHECK_BIT_BUFFER(state,n,action); * Ensure there are N bits in get_buffer; if suspend, take action. * val = GET_BITS(n); * Fetch next N bits. * val = PEEK_BITS(n); * Fetch next N bits without removing them from the buffer. * DROP_BITS(n); * Discard next N bits. * The value N should be a simple variable, not an expression, because it * is evaluated multiple times. */ protected static bool CHECK_BIT_BUFFER(ref bitread_working_state state, int nbits, ref int get_buffer, ref int bits_left) { if (bits_left < nbits) { if (!jpeg_fill_bit_buffer(ref state, get_buffer, bits_left, nbits)) { return(false); } get_buffer = state.get_buffer; bits_left = state.bits_left; } return(true); }
/* * Code for extracting next Huffman-coded symbol from input bit stream. * Again, this is time-critical and we make the main paths be macros. * * We use a lookahead table to process codes of up to HUFF_LOOKAHEAD bits * without looping. Usually, more than 95% of the Huffman codes will be 8 * or fewer bits long. The few overlength codes are handled with a loop, * which need not be inline code. * * Notes about the HUFF_DECODE macro: * 1. Near the end of the data segment, we may fail to get enough bits * for a lookahead. In that case, we do it the hard way. * 2. If the lookahead table contains no entry, the next code must be * more than HUFF_LOOKAHEAD bits long. * 3. jpeg_huff_decode returns -1 if forced to suspend. */ protected static bool HUFF_DECODE(out int result, ref bitread_working_state state, d_derived_tbl htbl, ref int get_buffer, ref int bits_left) { int nb = 0; bool doSlow = false; if (bits_left < JpegConstants.HUFF_LOOKAHEAD) { if (!jpeg_fill_bit_buffer(ref state, get_buffer, bits_left, 0)) { result = -1; return(false); } get_buffer = state.get_buffer; bits_left = state.bits_left; if (bits_left < JpegConstants.HUFF_LOOKAHEAD) { nb = 1; doSlow = true; } } if (!doSlow) { int look = PEEK_BITS(JpegConstants.HUFF_LOOKAHEAD, get_buffer, bits_left); if ((nb = htbl.look_nbits[look]) != 0) { DROP_BITS(nb, ref bits_left); result = htbl.look_sym[look]; return(true); } nb = JpegConstants.HUFF_LOOKAHEAD + 1; } result = jpeg_huff_decode(ref state, get_buffer, bits_left, htbl, nb); if (result < 0) { return(false); } get_buffer = state.get_buffer; bits_left = state.bits_left; return(true); }
/* Out-of-line case for Huffman code fetching */ protected static int jpeg_huff_decode(ref bitread_working_state state, int get_buffer, int bits_left, d_derived_tbl htbl, int min_bits) { /* HUFF_DECODE has determined that the code is at least min_bits */ /* bits long, so fetch that many bits in one swoop. */ int l = min_bits; if (!CHECK_BIT_BUFFER(ref state, l, ref get_buffer, ref bits_left)) { return(-1); } int code = GET_BITS(l, get_buffer, ref bits_left); /* Collect the rest of the Huffman code one bit at a time. */ /* This is per Figure F.16 in the JPEG spec. */ while (code > htbl.maxcode[l]) { code <<= 1; if (!CHECK_BIT_BUFFER(ref state, 1, ref get_buffer, ref bits_left)) { return(-1); } code |= GET_BITS(1, get_buffer, ref bits_left); l++; } /* Unload the local registers */ state.get_buffer = get_buffer; state.bits_left = bits_left; /* With garbage input we may reach the sentinel value l = 17. */ if (l > 16) { state.cinfo.WARNMS(J_MESSAGE_CODE.JWRN_HUFF_BAD_CODE); /* fake a zero as the safest result */ return(0); } return(htbl.pub.Huffval[code + htbl.valoffset[l]]); }
/* * These methods provide the in-line portion of bit fetching. * Use CHECK_BIT_BUFFER to ensure there are N bits in get_buffer * before using GET_BITS, PEEK_BITS, or DROP_BITS. * The variables get_buffer and bits_left are assumed to be locals, * but the state struct might not be (jpeg_huff_decode needs this). * CHECK_BIT_BUFFER(state,n,action); * Ensure there are N bits in get_buffer; if suspend, take action. * val = GET_BITS(n); * Fetch next N bits. * val = PEEK_BITS(n); * Fetch next N bits without removing them from the buffer. * DROP_BITS(n); * Discard next N bits. * The value N should be a simple variable, not an expression, because it * is evaluated multiple times. */ protected static bool CHECK_BIT_BUFFER(ref bitread_working_state state, int nbits, ref int get_buffer, ref int bits_left) { if (bits_left < nbits) { if (!jpeg_fill_bit_buffer(ref state, get_buffer, bits_left, nbits)) return false; get_buffer = state.get_buffer; bits_left = state.bits_left; } return true; }
/// <summary> /// Decode and return one MCU's worth of Huffman-compressed coefficients. /// The coefficients are reordered from zigzag order into natural array order, /// but are not dequantized. /// /// The i'th block of the MCU is stored into the block pointed to by /// MCU_data[i]. WE ASSUME THIS AREA HAS BEEN ZEROED BY THE CALLER. /// (Wholesale zeroing is usually a little faster than retail...) /// /// Returns false if data source requested suspension. In that case no /// changes have been made to permanent state. (Exception: some output /// coefficients may already have been assigned. This is harmless for /// this module, since we'll just re-assign them on the next call.) /// </summary> public override bool decode_mcu(JBLOCK[] MCU_data) { /* Process restart marker if needed; may have to suspend */ if (m_cinfo.m_restart_interval != 0) { if (m_restarts_to_go == 0) { if (!process_restart()) return false; } } /* If we've run out of data, just leave the MCU set to zeroes. * This way, we return uniform gray for the remainder of the segment. */ if (!m_insufficient_data) { /* Load up working state */ int get_buffer; int bits_left; bitread_working_state br_state = new bitread_working_state(); BITREAD_LOAD_STATE(m_bitstate, out get_buffer, out bits_left, ref br_state); savable_state state = new savable_state(); state.Assign(m_saved); /* Outer loop handles each block in the MCU */ for (int blkn = 0; blkn < m_cinfo.m_blocks_in_MCU; blkn++) { /* Decode a single block's worth of coefficients */ /* Section F.2.2.1: decode the DC coefficient difference */ int s; if (!HUFF_DECODE(out s, ref br_state, m_dc_cur_tbls[blkn], ref get_buffer, ref bits_left)) return false; if (s != 0) { if (!CHECK_BIT_BUFFER(ref br_state, s, ref get_buffer, ref bits_left)) return false; int r = GET_BITS(s, get_buffer, ref bits_left); s = HUFF_EXTEND(r, s); } if (m_dc_needed[blkn]) { /* Convert DC difference to actual value, update last_dc_val */ int ci = m_cinfo.m_MCU_membership[blkn]; s += state.last_dc_val[ci]; state.last_dc_val[ci] = s; /* Output the DC coefficient (assumes jpeg_natural_order[0] = 0) */ MCU_data[blkn][0] = (short) s; } if (m_ac_needed[blkn]) { /* Section F.2.2.2: decode the AC coefficients */ /* Since zeroes are skipped, output area must be cleared beforehand */ for (int k = 1; k < JpegConstants.DCTSIZE2; k++) { if (!HUFF_DECODE(out s, ref br_state, m_ac_cur_tbls[blkn], ref get_buffer, ref bits_left)) return false; int r = s >> 4; s &= 15; if (s != 0) { k += r; if (!CHECK_BIT_BUFFER(ref br_state, s, ref get_buffer, ref bits_left)) return false; r = GET_BITS(s, get_buffer, ref bits_left); s = HUFF_EXTEND(r, s); /* Output coefficient in natural (dezigzagged) order. * Note: the extra entries in jpeg_natural_order[] will save us * if k >= DCTSIZE2, which could happen if the data is corrupted. */ MCU_data[blkn][JpegUtils.jpeg_natural_order[k]] = (short) s; } else { if (r != 15) break; k += 15; } } } else { /* Section F.2.2.2: decode the AC coefficients */ /* In this path we just discard the values */ for (int k = 1; k < JpegConstants.DCTSIZE2; k++) { if (!HUFF_DECODE(out s, ref br_state, m_ac_cur_tbls[blkn], ref get_buffer, ref bits_left)) return false; int r = s >> 4; s &= 15; if (s != 0) { k += r; if (!CHECK_BIT_BUFFER(ref br_state, s, ref get_buffer, ref bits_left)) return false; DROP_BITS(s, ref bits_left); } else { if (r != 15) break; k += 15; } } } } /* Completed MCU, so update state */ BITREAD_SAVE_STATE(ref m_bitstate, get_buffer, bits_left); m_saved.Assign(state); } /* Account for restart interval (no-op if not using restarts) */ m_restarts_to_go--; return true; }
/// <summary> /// Decode and return one MCU's worth of Huffman-compressed coefficients. /// The coefficients are reordered from zigzag order into natural array order, /// but are not dequantized. /// /// The i'th block of the MCU is stored into the block pointed to by /// MCU_data[i]. WE ASSUME THIS AREA HAS BEEN ZEROED BY THE CALLER. /// (Wholesale zeroing is usually a little faster than retail...) /// /// Returns false if data source requested suspension. In that case no /// changes have been made to permanent state. (Exception: some output /// coefficients may already have been assigned. This is harmless for /// this module, since we'll just re-assign them on the next call.) /// </summary> public override bool decode_mcu(JBLOCK[] MCU_data) { /* Process restart marker if needed; may have to suspend */ if (m_cinfo.m_restart_interval != 0) { if (m_restarts_to_go == 0) { if (!process_restart()) { return(false); } } } /* If we've run out of data, just leave the MCU set to zeroes. * This way, we return uniform gray for the remainder of the segment. */ if (!m_insufficient_data) { /* Load up working state */ int get_buffer; int bits_left; bitread_working_state br_state = new bitread_working_state(); BITREAD_LOAD_STATE(m_bitstate, out get_buffer, out bits_left, ref br_state); savable_state state = new savable_state(); state.Assign(m_saved); /* Outer loop handles each block in the MCU */ for (int blkn = 0; blkn < m_cinfo.m_blocks_in_MCU; blkn++) { /* Decode a single block's worth of coefficients */ /* Section F.2.2.1: decode the DC coefficient difference */ int s; if (!HUFF_DECODE(out s, ref br_state, m_dc_cur_tbls[blkn], ref get_buffer, ref bits_left)) { return(false); } if (s != 0) { if (!CHECK_BIT_BUFFER(ref br_state, s, ref get_buffer, ref bits_left)) { return(false); } int r = GET_BITS(s, get_buffer, ref bits_left); s = HUFF_EXTEND(r, s); } if (m_dc_needed[blkn]) { /* Convert DC difference to actual value, update last_dc_val */ int ci = m_cinfo.m_MCU_membership[blkn]; s += state.last_dc_val[ci]; state.last_dc_val[ci] = s; /* Output the DC coefficient (assumes jpeg_natural_order[0] = 0) */ MCU_data[blkn][0] = (short)s; } if (m_ac_needed[blkn]) { /* Section F.2.2.2: decode the AC coefficients */ /* Since zeroes are skipped, output area must be cleared beforehand */ for (int k = 1; k < JpegConstants.DCTSIZE2; k++) { if (!HUFF_DECODE(out s, ref br_state, m_ac_cur_tbls[blkn], ref get_buffer, ref bits_left)) { return(false); } int r = s >> 4; s &= 15; if (s != 0) { k += r; if (!CHECK_BIT_BUFFER(ref br_state, s, ref get_buffer, ref bits_left)) { return(false); } r = GET_BITS(s, get_buffer, ref bits_left); s = HUFF_EXTEND(r, s); /* Output coefficient in natural (dezigzagged) order. * Note: the extra entries in jpeg_natural_order[] will save us * if k >= DCTSIZE2, which could happen if the data is corrupted. */ MCU_data[blkn][JpegUtils.jpeg_natural_order[k]] = (short)s; } else { if (r != 15) { break; } k += 15; } } } else { /* Section F.2.2.2: decode the AC coefficients */ /* In this path we just discard the values */ for (int k = 1; k < JpegConstants.DCTSIZE2; k++) { if (!HUFF_DECODE(out s, ref br_state, m_ac_cur_tbls[blkn], ref get_buffer, ref bits_left)) { return(false); } int r = s >> 4; s &= 15; if (s != 0) { k += r; if (!CHECK_BIT_BUFFER(ref br_state, s, ref get_buffer, ref bits_left)) { return(false); } DROP_BITS(s, ref bits_left); } else { if (r != 15) { break; } k += 15; } } } } /* Completed MCU, so update state */ BITREAD_SAVE_STATE(ref m_bitstate, get_buffer, bits_left); m_saved.Assign(state); } /* Account for restart interval (no-op if not using restarts) */ m_restarts_to_go--; return(true); }
protected void BITREAD_LOAD_STATE(bitread_perm_state bitstate, out int get_buffer, out int bits_left, ref bitread_working_state br_state) { br_state.cinfo = m_cinfo; get_buffer = bitstate.get_buffer; bits_left = bitstate.bits_left; }
/// <summary> /// MCU decoding for AC initial scan (either spectral selection, /// or first pass of successive approximation). /// </summary> private bool decode_mcu_AC_first(JBLOCK[] MCU_data) { /* Process restart marker if needed; may have to suspend */ if (m_cinfo.m_restart_interval != 0) { if (m_restarts_to_go == 0) { if (!process_restart()) { return(false); } } } /* If we've run out of data, just leave the MCU set to zeroes. * This way, we return uniform gray for the remainder of the segment. */ if (!m_insufficient_data) { /* Load up working state. * We can avoid loading/saving bitread state if in an EOB run. */ int EOBRUN = m_saved.EOBRUN; /* only part of saved state we need */ /* There is always only one block per MCU */ if (EOBRUN > 0) { /* if it's a band of zeroes... */ /* ...process it now (we do nothing) */ EOBRUN--; } else { int get_buffer; int bits_left; bitread_working_state br_state = new bitread_working_state(); BITREAD_LOAD_STATE(m_bitstate, out get_buffer, out bits_left, ref br_state); for (int k = m_cinfo.m_Ss; k <= m_cinfo.m_Se; k++) { int s; if (!HUFF_DECODE(out s, ref br_state, m_ac_derived_tbl, ref get_buffer, ref bits_left)) { return(false); } int r = s >> 4; s &= 15; if (s != 0) { k += r; if (!CHECK_BIT_BUFFER(ref br_state, s, ref get_buffer, ref bits_left)) { return(false); } r = GET_BITS(s, get_buffer, ref bits_left); s = HUFF_EXTEND(r, s); /* Scale and output coefficient in natural (dezigzagged) order */ MCU_data[0][JpegUtils.jpeg_natural_order[k]] = (short)(s << m_cinfo.m_Al); } else { if (r == 15) { /* ZRL */ k += 15; /* skip 15 zeroes in band */ } else { /* EOBr, run length is 2^r + appended bits */ EOBRUN = 1 << r; if (r != 0) { /* EOBr, r > 0 */ if (!CHECK_BIT_BUFFER(ref br_state, r, ref get_buffer, ref bits_left)) { return(false); } r = GET_BITS(r, get_buffer, ref bits_left); EOBRUN += r; } EOBRUN--; /* this band is processed at this moment */ break; /* force end-of-band */ } } } BITREAD_SAVE_STATE(ref m_bitstate, get_buffer, bits_left); } /* Completed MCU, so update state */ m_saved.EOBRUN = EOBRUN; /* only part of saved state we need */ } /* Account for restart interval (no-op if not using restarts) */ m_restarts_to_go--; return(true); }
/* Out-of-line case for Huffman code fetching */ protected static int jpeg_huff_decode(ref bitread_working_state state, int get_buffer, int bits_left, d_derived_tbl htbl, int min_bits) { /* HUFF_DECODE has determined that the code is at least min_bits */ /* bits long, so fetch that many bits in one swoop. */ int l = min_bits; if (!CHECK_BIT_BUFFER(ref state, l, ref get_buffer, ref bits_left)) return -1; int code = GET_BITS(l, get_buffer, ref bits_left); /* Collect the rest of the Huffman code one bit at a time. */ /* This is per Figure F.16 in the JPEG spec. */ while (code > htbl.maxcode[l]) { code <<= 1; if (!CHECK_BIT_BUFFER(ref state, 1, ref get_buffer, ref bits_left)) return -1; code |= GET_BITS(1, get_buffer, ref bits_left); l++; } /* Unload the local registers */ state.get_buffer = get_buffer; state.bits_left = bits_left; /* With garbage input we may reach the sentinel value l = 17. */ if (l > 16) { state.cinfo.WARNMS(J_MESSAGE_CODE.JWRN_HUFF_BAD_CODE); /* fake a zero as the safest result */ return 0; } return htbl.pub.Huffval[code + htbl.valoffset[l]]; }
/// <summary> /// MCU decoding for DC successive approximation refinement scan. /// Note: we assume such scans can be multi-component, although the spec /// is not very clear on the point. /// </summary> private bool decode_mcu_DC_refine(JBLOCK[] MCU_data) { /* Process restart marker if needed; may have to suspend */ if (m_cinfo.m_restart_interval != 0) { if (m_restarts_to_go == 0) { if (!process_restart()) return false; } } /* Not worth the cycles to check insufficient_data here, * since we will not change the data anyway if we read zeroes. */ /* Load up working state */ int get_buffer; int bits_left; bitread_working_state br_state = new bitread_working_state(); BITREAD_LOAD_STATE(m_bitstate, out get_buffer, out bits_left, ref br_state); /* Outer loop handles each block in the MCU */ for (int blkn = 0; blkn < m_cinfo.m_blocks_in_MCU; blkn++) { /* Encoded data is simply the next bit of the two's-complement DC value */ if (!CHECK_BIT_BUFFER(ref br_state, 1, ref get_buffer, ref bits_left)) return false; if (GET_BITS(1, get_buffer, ref bits_left) != 0) { /* 1 in the bit position being coded */ MCU_data[blkn][0] = (short)((ushort)MCU_data[blkn][0] | (ushort)(1 << m_cinfo.m_Al)); } /* Note: since we use |=, repeating the assignment later is safe */ } /* Completed MCU, so update state */ BITREAD_SAVE_STATE(ref m_bitstate, get_buffer, bits_left); /* Account for restart interval (no-op if not using restarts) */ m_restarts_to_go--; return true; }
/* * Huffman MCU decoding. * Each of these routines decodes and returns one MCU's worth of * Huffman-compressed coefficients. * The coefficients are reordered from zigzag order into natural array order, * but are not dequantized. * * The i'th block of the MCU is stored into the block pointed to by * MCU_data[i]. WE ASSUME THIS AREA IS INITIALLY ZEROED BY THE CALLER. * * We return false if data source requested suspension. In that case no * changes have been made to permanent state. (Exception: some output * coefficients may already have been assigned. This is harmless for * spectral selection, since we'll just re-assign them on the next call. * Successive approximation AC refinement has to be more careful, however.) */ /// <summary> /// MCU decoding for DC initial scan (either spectral selection, /// or first pass of successive approximation). /// </summary> private bool decode_mcu_DC_first(JBLOCK[] MCU_data) { /* Process restart marker if needed; may have to suspend */ if (m_cinfo.m_restart_interval != 0) { if (m_restarts_to_go == 0) { if (!process_restart()) return false; } } /* If we've run out of data, just leave the MCU set to zeroes. * This way, we return uniform gray for the remainder of the segment. */ if (!m_insufficient_data) { /* Load up working state */ int get_buffer; int bits_left; bitread_working_state br_state = new bitread_working_state(); BITREAD_LOAD_STATE(m_bitstate, out get_buffer, out bits_left, ref br_state); savable_state state = new savable_state(); state.Assign(m_saved); /* Outer loop handles each block in the MCU */ for (int blkn = 0; blkn < m_cinfo.m_blocks_in_MCU; blkn++) { int ci = m_cinfo.m_MCU_membership[blkn]; /* Decode a single block's worth of coefficients */ /* Section F.2.2.1: decode the DC coefficient difference */ int s; if (!HUFF_DECODE(out s, ref br_state, m_derived_tbls[m_cinfo.Comp_info[m_cinfo.m_cur_comp_info[ci]].Dc_tbl_no], ref get_buffer, ref bits_left)) return false; if (s != 0) { if (!CHECK_BIT_BUFFER(ref br_state, s, ref get_buffer, ref bits_left)) return false; int r = GET_BITS(s, get_buffer, ref bits_left); s = HUFF_EXTEND(r, s); } /* Convert DC difference to actual value, update last_dc_val */ s += state.last_dc_val[ci]; state.last_dc_val[ci] = s; /* Scale and output the coefficient (assumes jpeg_natural_order[0]=0) */ MCU_data[blkn][0] = (short)(s << m_cinfo.m_Al); } /* Completed MCU, so update state */ BITREAD_SAVE_STATE(ref m_bitstate, get_buffer, bits_left); m_saved.Assign(state); } /* Account for restart interval (no-op if not using restarts) */ m_restarts_to_go--; return true; }
// There is always only one block per MCU private bool decode_mcu_AC_refine(JBLOCK[] MCU_data) { int p1 = 1 << m_cinfo.m_Al; /* 1 in the bit position being coded */ int m1 = -1 << m_cinfo.m_Al; /* -1 in the bit position being coded */ /* Process restart marker if needed; may have to suspend */ if (m_cinfo.m_restart_interval != 0) { if (m_restarts_to_go == 0) { if (!process_restart()) return false; } } /* If we've run out of data, don't modify the MCU. */ if (!m_insufficient_data) { /* Load up working state */ int get_buffer; int bits_left; bitread_working_state br_state = new bitread_working_state(); BITREAD_LOAD_STATE(m_bitstate, out get_buffer, out bits_left, ref br_state); int EOBRUN = m_saved.EOBRUN; /* only part of saved state we need */ /* If we are forced to suspend, we must undo the assignments to any newly * nonzero coefficients in the block, because otherwise we'd get confused * next time about which coefficients were already nonzero. * But we need not undo addition of bits to already-nonzero coefficients; * instead, we can test the current bit to see if we already did it. */ int num_newnz = 0; int[] newnz_pos = new int[JpegConstants.DCTSIZE2]; /* initialize coefficient loop counter to start of band */ int k = m_cinfo.m_Ss; if (EOBRUN == 0) { for (; k <= m_cinfo.m_Se; k++) { int s; if (!HUFF_DECODE(out s, ref br_state, m_ac_derived_tbl, ref get_buffer, ref bits_left)) { undo_decode_mcu_AC_refine(MCU_data, newnz_pos, num_newnz); return false; } int r = s >> 4; s &= 15; if (s != 0) { if (s != 1) { /* size of new coef should always be 1 */ m_cinfo.WARNMS(J_MESSAGE_CODE.JWRN_HUFF_BAD_CODE); } if (!CHECK_BIT_BUFFER(ref br_state, 1, ref get_buffer, ref bits_left)) { undo_decode_mcu_AC_refine(MCU_data, newnz_pos, num_newnz); return false; } if (GET_BITS(1, get_buffer, ref bits_left) != 0) { /* newly nonzero coef is positive */ s = p1; } else { /* newly nonzero coef is negative */ s = m1; } } else { if (r != 15) { EOBRUN = 1 << r; /* EOBr, run length is 2^r + appended bits */ if (r != 0) { if (!CHECK_BIT_BUFFER(ref br_state, r, ref get_buffer, ref bits_left)) { undo_decode_mcu_AC_refine(MCU_data, newnz_pos, num_newnz); return false; } r = GET_BITS(r, get_buffer, ref bits_left); EOBRUN += r; } break; /* rest of block is handled by EOB logic */ } /* note s = 0 for processing ZRL */ } /* Advance over already-nonzero coefs and r still-zero coefs, * appending correction bits to the nonzeroes. A correction bit is 1 * if the absolute value of the coefficient must be increased. */ do { int blockIndex = JpegUtils.jpeg_natural_order[k]; short thiscoef = MCU_data[0][blockIndex]; if (thiscoef != 0) { if (!CHECK_BIT_BUFFER(ref br_state, 1, ref get_buffer, ref bits_left)) { undo_decode_mcu_AC_refine(MCU_data, newnz_pos, num_newnz); return false; } if (GET_BITS(1, get_buffer, ref bits_left) != 0) { if ((thiscoef & p1) == 0) { /* do nothing if already set it */ if (thiscoef >= 0) MCU_data[0][blockIndex] += (short)p1; else MCU_data[0][blockIndex] += (short)m1; } } } else { if (--r < 0) break; /* reached target zero coefficient */ } k++; } while (k <= m_cinfo.m_Se); if (s != 0) { int pos = JpegUtils.jpeg_natural_order[k]; /* Output newly nonzero coefficient */ MCU_data[0][pos] = (short)s; /* Remember its position in case we have to suspend */ newnz_pos[num_newnz++] = pos; } } } if (EOBRUN > 0) { /* Scan any remaining coefficient positions after the end-of-band * (the last newly nonzero coefficient, if any). Append a correction * bit to each already-nonzero coefficient. A correction bit is 1 * if the absolute value of the coefficient must be increased. */ for (; k <= m_cinfo.m_Se; k++) { int blockIndex = JpegUtils.jpeg_natural_order[k]; short thiscoef = MCU_data[0][blockIndex]; if (thiscoef != 0) { if (!CHECK_BIT_BUFFER(ref br_state, 1, ref get_buffer, ref bits_left)) { //undo_decode_mcu_AC_refine(MCU_data[0], newnz_pos, num_newnz); undo_decode_mcu_AC_refine(MCU_data, newnz_pos, num_newnz); return false; } if (GET_BITS(1, get_buffer, ref bits_left) != 0) { if ((thiscoef & p1) == 0) { /* do nothing if already changed it */ if (thiscoef >= 0) MCU_data[0][blockIndex] += (short)p1; else MCU_data[0][blockIndex] += (short)m1; } } } } /* Count one block completed in EOB run */ EOBRUN--; } /* Completed MCU, so update state */ BITREAD_SAVE_STATE(ref m_bitstate, get_buffer, bits_left); m_saved.EOBRUN = EOBRUN; /* only part of saved state we need */ } /* Account for restart interval (no-op if not using restarts) */ m_restarts_to_go--; return true; }
/// <summary> /// MCU decoding for AC initial scan (either spectral selection, /// or first pass of successive approximation). /// </summary> private bool decode_mcu_AC_first(JBLOCK[] MCU_data) { /* Process restart marker if needed; may have to suspend */ if (m_cinfo.m_restart_interval != 0) { if (m_restarts_to_go == 0) { if (!process_restart()) return false; } } /* If we've run out of data, just leave the MCU set to zeroes. * This way, we return uniform gray for the remainder of the segment. */ if (!m_insufficient_data) { /* Load up working state. * We can avoid loading/saving bitread state if in an EOB run. */ int EOBRUN = m_saved.EOBRUN; /* only part of saved state we need */ /* There is always only one block per MCU */ if (EOBRUN > 0) { /* if it's a band of zeroes... */ /* ...process it now (we do nothing) */ EOBRUN--; } else { int get_buffer; int bits_left; bitread_working_state br_state = new bitread_working_state(); BITREAD_LOAD_STATE(m_bitstate, out get_buffer, out bits_left, ref br_state); for (int k = m_cinfo.m_Ss; k <= m_cinfo.m_Se; k++) { int s; if (!HUFF_DECODE(out s, ref br_state, m_ac_derived_tbl, ref get_buffer, ref bits_left)) return false; int r = s >> 4; s &= 15; if (s != 0) { k += r; if (!CHECK_BIT_BUFFER(ref br_state, s, ref get_buffer, ref bits_left)) return false; r = GET_BITS(s, get_buffer, ref bits_left); s = HUFF_EXTEND(r, s); /* Scale and output coefficient in natural (dezigzagged) order */ MCU_data[0][JpegUtils.jpeg_natural_order[k]] = (short)(s << m_cinfo.m_Al); } else { if (r == 15) { /* ZRL */ k += 15; /* skip 15 zeroes in band */ } else { /* EOBr, run length is 2^r + appended bits */ EOBRUN = 1 << r; if (r != 0) { /* EOBr, r > 0 */ if (!CHECK_BIT_BUFFER(ref br_state, r, ref get_buffer, ref bits_left)) return false; r = GET_BITS(r, get_buffer, ref bits_left); EOBRUN += r; } EOBRUN--; /* this band is processed at this moment */ break; /* force end-of-band */ } } } BITREAD_SAVE_STATE(ref m_bitstate, get_buffer, bits_left); } /* Completed MCU, so update state */ m_saved.EOBRUN = EOBRUN; /* only part of saved state we need */ } /* Account for restart interval (no-op if not using restarts) */ m_restarts_to_go--; return true; }
// There is always only one block per MCU private bool decode_mcu_AC_refine(JBLOCK[] MCU_data) { int p1 = 1 << m_cinfo.m_Al; /* 1 in the bit position being coded */ int m1 = -1 << m_cinfo.m_Al; /* -1 in the bit position being coded */ /* Process restart marker if needed; may have to suspend */ if (m_cinfo.m_restart_interval != 0) { if (m_restarts_to_go == 0) { if (!process_restart()) { return(false); } } } /* If we've run out of data, don't modify the MCU. */ if (!m_insufficient_data) { /* Load up working state */ int get_buffer; int bits_left; bitread_working_state br_state = new bitread_working_state(); BITREAD_LOAD_STATE(m_bitstate, out get_buffer, out bits_left, ref br_state); int EOBRUN = m_saved.EOBRUN; /* only part of saved state we need */ /* If we are forced to suspend, we must undo the assignments to any newly * nonzero coefficients in the block, because otherwise we'd get confused * next time about which coefficients were already nonzero. * But we need not undo addition of bits to already-nonzero coefficients; * instead, we can test the current bit to see if we already did it. */ int num_newnz = 0; int[] newnz_pos = new int[JpegConstants.DCTSIZE2]; /* initialize coefficient loop counter to start of band */ int k = m_cinfo.m_Ss; if (EOBRUN == 0) { for (; k <= m_cinfo.m_Se; k++) { int s; if (!HUFF_DECODE(out s, ref br_state, m_ac_derived_tbl, ref get_buffer, ref bits_left)) { undo_decode_mcu_AC_refine(MCU_data, newnz_pos, num_newnz); return(false); } int r = s >> 4; s &= 15; if (s != 0) { if (s != 1) { /* size of new coef should always be 1 */ m_cinfo.WARNMS(J_MESSAGE_CODE.JWRN_HUFF_BAD_CODE); } if (!CHECK_BIT_BUFFER(ref br_state, 1, ref get_buffer, ref bits_left)) { undo_decode_mcu_AC_refine(MCU_data, newnz_pos, num_newnz); return(false); } if (GET_BITS(1, get_buffer, ref bits_left) != 0) { /* newly nonzero coef is positive */ s = p1; } else { /* newly nonzero coef is negative */ s = m1; } } else { if (r != 15) { EOBRUN = 1 << r; /* EOBr, run length is 2^r + appended bits */ if (r != 0) { if (!CHECK_BIT_BUFFER(ref br_state, r, ref get_buffer, ref bits_left)) { undo_decode_mcu_AC_refine(MCU_data, newnz_pos, num_newnz); return(false); } r = GET_BITS(r, get_buffer, ref bits_left); EOBRUN += r; } break; /* rest of block is handled by EOB logic */ } /* note s = 0 for processing ZRL */ } /* Advance over already-nonzero coefs and r still-zero coefs, * appending correction bits to the nonzeroes. A correction bit is 1 * if the absolute value of the coefficient must be increased. */ do { int blockIndex = JpegUtils.jpeg_natural_order[k]; short thiscoef = MCU_data[0][blockIndex]; if (thiscoef != 0) { if (!CHECK_BIT_BUFFER(ref br_state, 1, ref get_buffer, ref bits_left)) { undo_decode_mcu_AC_refine(MCU_data, newnz_pos, num_newnz); return(false); } if (GET_BITS(1, get_buffer, ref bits_left) != 0) { if ((thiscoef & p1) == 0) { /* do nothing if already set it */ if (thiscoef >= 0) { MCU_data[0][blockIndex] += (short)p1; } else { MCU_data[0][blockIndex] += (short)m1; } } } } else { if (--r < 0) { break; /* reached target zero coefficient */ } } k++; }while (k <= m_cinfo.m_Se); if (s != 0) { int pos = JpegUtils.jpeg_natural_order[k]; /* Output newly nonzero coefficient */ MCU_data[0][pos] = (short)s; /* Remember its position in case we have to suspend */ newnz_pos[num_newnz++] = pos; } } } if (EOBRUN > 0) { /* Scan any remaining coefficient positions after the end-of-band * (the last newly nonzero coefficient, if any). Append a correction * bit to each already-nonzero coefficient. A correction bit is 1 * if the absolute value of the coefficient must be increased. */ for (; k <= m_cinfo.m_Se; k++) { int blockIndex = JpegUtils.jpeg_natural_order[k]; short thiscoef = MCU_data[0][blockIndex]; if (thiscoef != 0) { if (!CHECK_BIT_BUFFER(ref br_state, 1, ref get_buffer, ref bits_left)) { //undo_decode_mcu_AC_refine(MCU_data[0], newnz_pos, num_newnz); undo_decode_mcu_AC_refine(MCU_data, newnz_pos, num_newnz); return(false); } if (GET_BITS(1, get_buffer, ref bits_left) != 0) { if ((thiscoef & p1) == 0) { /* do nothing if already changed it */ if (thiscoef >= 0) { MCU_data[0][blockIndex] += (short)p1; } else { MCU_data[0][blockIndex] += (short)m1; } } } } } /* Count one block completed in EOB run */ EOBRUN--; } /* Completed MCU, so update state */ BITREAD_SAVE_STATE(ref m_bitstate, get_buffer, bits_left); m_saved.EOBRUN = EOBRUN; /* only part of saved state we need */ } /* Account for restart interval (no-op if not using restarts) */ m_restarts_to_go--; return(true); }
/* Load up the bit buffer to a depth of at least nbits */ protected static bool jpeg_fill_bit_buffer(ref bitread_working_state state, int get_buffer, int bits_left, int nbits) { /* Attempt to load at least MIN_GET_BITS bits into get_buffer. */ /* (It is assumed that no request will be for more than that many bits.) */ /* We fail to do so only if we hit a marker or are forced to suspend. */ bool noMoreBytes = false; if (state.cinfo.m_unread_marker == 0) { /* cannot advance past a marker */ while (bits_left < MIN_GET_BITS) { int c; state.cinfo.m_src.GetByte(out c); /* If it's 0xFF, check and discard stuffed zero byte */ if (c == 0xFF) { /* Loop here to discard any padding FF's on terminating marker, * so that we can save a valid unread_marker value. NOTE: we will * accept multiple FF's followed by a 0 as meaning a single FF data * byte. This data pattern is not valid according to the standard. */ do { state.cinfo.m_src.GetByte(out c); } while (c == 0xFF); if (c == 0) { /* Found FF/00, which represents an FF data byte */ c = 0xFF; } else { /* Oops, it's actually a marker indicating end of compressed data. * Save the marker code for later use. * Fine point: it might appear that we should save the marker into * bitread working state, not straight into permanent state. But * once we have hit a marker, we cannot need to suspend within the * current MCU, because we will read no more bytes from the data * source. So it is OK to update permanent state right away. */ state.cinfo.m_unread_marker = c; /* See if we need to insert some fake zero bits. */ noMoreBytes = true; break; } } /* OK, load c into get_buffer */ get_buffer = (get_buffer << 8) | c; bits_left += 8; } /* end while */ } else noMoreBytes = true; if (noMoreBytes) { /* We get here if we've read the marker that terminates the compressed * data segment. There should be enough bits in the buffer register * to satisfy the request; if so, no problem. */ if (nbits > bits_left) { /* Uh-oh. Report corrupted data to user and stuff zeroes into * the data stream, so that we can produce some kind of image. * We use a nonvolatile flag to ensure that only one warning message * appears per data segment. */ if (!state.cinfo.m_entropy.m_insufficient_data) { state.cinfo.WARNMS(J_MESSAGE_CODE.JWRN_HIT_MARKER); state.cinfo.m_entropy.m_insufficient_data = true; } /* Fill the buffer with zero bits */ get_buffer <<= MIN_GET_BITS - bits_left; bits_left = MIN_GET_BITS; } } /* Unload the local registers */ state.get_buffer = get_buffer; state.bits_left = bits_left; return true; }
/* * Code for extracting next Huffman-coded symbol from input bit stream. * Again, this is time-critical and we make the main paths be macros. * * We use a lookahead table to process codes of up to HUFF_LOOKAHEAD bits * without looping. Usually, more than 95% of the Huffman codes will be 8 * or fewer bits long. The few overlength codes are handled with a loop, * which need not be inline code. * * Notes about the HUFF_DECODE macro: * 1. Near the end of the data segment, we may fail to get enough bits * for a lookahead. In that case, we do it the hard way. * 2. If the lookahead table contains no entry, the next code must be * more than HUFF_LOOKAHEAD bits long. * 3. jpeg_huff_decode returns -1 if forced to suspend. */ protected static bool HUFF_DECODE(out int result, ref bitread_working_state state, d_derived_tbl htbl, ref int get_buffer, ref int bits_left) { int nb = 0; bool doSlow = false; if (bits_left < JpegConstants.HUFF_LOOKAHEAD) { if (!jpeg_fill_bit_buffer(ref state, get_buffer, bits_left, 0)) { result = -1; return false; } get_buffer = state.get_buffer; bits_left = state.bits_left; if (bits_left < JpegConstants.HUFF_LOOKAHEAD) { nb = 1; doSlow = true; } } if (!doSlow) { int look = PEEK_BITS(JpegConstants.HUFF_LOOKAHEAD, get_buffer, bits_left); if ((nb = htbl.look_nbits[look]) != 0) { DROP_BITS(nb, ref bits_left); result = htbl.look_sym[look]; return true; } nb = JpegConstants.HUFF_LOOKAHEAD + 1; } result = jpeg_huff_decode(ref state, get_buffer, bits_left, htbl, nb); if (result < 0) return false; get_buffer = state.get_buffer; bits_left = state.bits_left; return true; }
/* Load up the bit buffer to a depth of at least nbits */ protected static bool jpeg_fill_bit_buffer(ref bitread_working_state state, int get_buffer, int bits_left, int nbits) { /* Attempt to load at least MIN_GET_BITS bits into get_buffer. */ /* (It is assumed that no request will be for more than that many bits.) */ /* We fail to do so only if we hit a marker or are forced to suspend. */ bool noMoreBytes = false; if (state.cinfo.m_unread_marker == 0) { /* cannot advance past a marker */ while (bits_left < MIN_GET_BITS) { int c; state.cinfo.m_src.GetByte(out c); /* If it's 0xFF, check and discard stuffed zero byte */ if (c == 0xFF) { /* Loop here to discard any padding FF's on terminating marker, * so that we can save a valid unread_marker value. NOTE: we will * accept multiple FF's followed by a 0 as meaning a single FF data * byte. This data pattern is not valid according to the standard. */ do { state.cinfo.m_src.GetByte(out c); }while (c == 0xFF); if (c == 0) { /* Found FF/00, which represents an FF data byte */ c = 0xFF; } else { /* Oops, it's actually a marker indicating end of compressed data. * Save the marker code for later use. * Fine point: it might appear that we should save the marker into * bitread working state, not straight into permanent state. But * once we have hit a marker, we cannot need to suspend within the * current MCU, because we will read no more bytes from the data * source. So it is OK to update permanent state right away. */ state.cinfo.m_unread_marker = c; /* See if we need to insert some fake zero bits. */ noMoreBytes = true; break; } } /* OK, load c into get_buffer */ get_buffer = (get_buffer << 8) | c; bits_left += 8; } /* end while */ } else { noMoreBytes = true; } if (noMoreBytes) { /* We get here if we've read the marker that terminates the compressed * data segment. There should be enough bits in the buffer register * to satisfy the request; if so, no problem. */ if (nbits > bits_left) { /* Uh-oh. Report corrupted data to user and stuff zeroes into * the data stream, so that we can produce some kind of image. * We use a nonvolatile flag to ensure that only one warning message * appears per data segment. */ if (!state.cinfo.m_entropy.m_insufficient_data) { state.cinfo.WARNMS(J_MESSAGE_CODE.JWRN_HIT_MARKER); state.cinfo.m_entropy.m_insufficient_data = true; } /* Fill the buffer with zero bits */ get_buffer <<= MIN_GET_BITS - bits_left; bits_left = MIN_GET_BITS; } } /* Unload the local registers */ state.get_buffer = get_buffer; state.bits_left = bits_left; return(true); }
/* * Huffman MCU decoding. * Each of these routines decodes and returns one MCU's worth of * Huffman-compressed coefficients. * The coefficients are reordered from zigzag order into natural array order, * but are not dequantized. * * The i'th block of the MCU is stored into the block pointed to by * MCU_data[i]. WE ASSUME THIS AREA IS INITIALLY ZEROED BY THE CALLER. * * We return false if data source requested suspension. In that case no * changes have been made to permanent state. (Exception: some output * coefficients may already have been assigned. This is harmless for * spectral selection, since we'll just re-assign them on the next call. * Successive approximation AC refinement has to be more careful, however.) */ /// <summary> /// MCU decoding for DC initial scan (either spectral selection, /// or first pass of successive approximation). /// </summary> private bool decode_mcu_DC_first(JBLOCK[] MCU_data) { /* Process restart marker if needed; may have to suspend */ if (m_cinfo.m_restart_interval != 0) { if (m_restarts_to_go == 0) { if (!process_restart()) { return(false); } } } /* If we've run out of data, just leave the MCU set to zeroes. * This way, we return uniform gray for the remainder of the segment. */ if (!m_insufficient_data) { /* Load up working state */ int get_buffer; int bits_left; bitread_working_state br_state = new bitread_working_state(); BITREAD_LOAD_STATE(m_bitstate, out get_buffer, out bits_left, ref br_state); savable_state state = new savable_state(); state.Assign(m_saved); /* Outer loop handles each block in the MCU */ for (int blkn = 0; blkn < m_cinfo.m_blocks_in_MCU; blkn++) { int ci = m_cinfo.m_MCU_membership[blkn]; /* Decode a single block's worth of coefficients */ /* Section F.2.2.1: decode the DC coefficient difference */ int s; if (!HUFF_DECODE(out s, ref br_state, m_derived_tbls[m_cinfo.Comp_info[m_cinfo.m_cur_comp_info[ci]].Dc_tbl_no], ref get_buffer, ref bits_left)) { return(false); } if (s != 0) { if (!CHECK_BIT_BUFFER(ref br_state, s, ref get_buffer, ref bits_left)) { return(false); } int r = GET_BITS(s, get_buffer, ref bits_left); s = HUFF_EXTEND(r, s); } /* Convert DC difference to actual value, update last_dc_val */ s += state.last_dc_val[ci]; state.last_dc_val[ci] = s; /* Scale and output the coefficient (assumes jpeg_natural_order[0]=0) */ MCU_data[blkn][0] = (short)(s << m_cinfo.m_Al); } /* Completed MCU, so update state */ BITREAD_SAVE_STATE(ref m_bitstate, get_buffer, bits_left); m_saved.Assign(state); } /* Account for restart interval (no-op if not using restarts) */ m_restarts_to_go--; return(true); }