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776 lines
23 KiB
776 lines
23 KiB
/* |
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* jdarith.c |
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* |
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* Developed 1997-2011 by Guido Vollbeding. |
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* This file is part of the Independent JPEG Group's software. |
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* For conditions of distribution and use, see the accompanying README file. |
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* |
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* This file contains portable arithmetic entropy decoding routines for JPEG |
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* (implementing the ISO/IEC IS 10918-1 and CCITT Recommendation ITU-T T.81). |
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* |
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* Both sequential and progressive modes are supported in this single module. |
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* |
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* Suspension is not currently supported in this module. |
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*/ |
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#define JPEG_INTERNALS |
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#include "jinclude.h" |
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#include "jpeglib.h" |
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/* Expanded entropy decoder object for arithmetic decoding. */ |
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typedef struct { |
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struct jpeg_entropy_decoder pub; /* public fields */ |
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INT32 c; /* C register, base of coding interval + input bit buffer */ |
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INT32 a; /* A register, normalized size of coding interval */ |
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int ct; /* bit shift counter, # of bits left in bit buffer part of C */ |
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/* init: ct = -16 */ |
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/* run: ct = 0..7 */ |
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/* error: ct = -1 */ |
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int last_dc_val[MAX_COMPS_IN_SCAN]; /* last DC coef for each component */ |
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int dc_context[MAX_COMPS_IN_SCAN]; /* context index for DC conditioning */ |
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unsigned int restarts_to_go; /* MCUs left in this restart interval */ |
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/* Pointers to statistics areas (these workspaces have image lifespan) */ |
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unsigned char * dc_stats[NUM_ARITH_TBLS]; |
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unsigned char * ac_stats[NUM_ARITH_TBLS]; |
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/* Statistics bin for coding with fixed probability 0.5 */ |
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unsigned char fixed_bin[4]; |
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} arith_entropy_decoder; |
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typedef arith_entropy_decoder * arith_entropy_ptr; |
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/* The following two definitions specify the allocation chunk size |
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* for the statistics area. |
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* According to sections F.1.4.4.1.3 and F.1.4.4.2, we need at least |
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* 49 statistics bins for DC, and 245 statistics bins for AC coding. |
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* |
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* We use a compact representation with 1 byte per statistics bin, |
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* thus the numbers directly represent byte sizes. |
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* This 1 byte per statistics bin contains the meaning of the MPS |
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* (more probable symbol) in the highest bit (mask 0x80), and the |
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* index into the probability estimation state machine table |
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* in the lower bits (mask 0x7F). |
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*/ |
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#define DC_STAT_BINS 64 |
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#define AC_STAT_BINS 256 |
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LOCAL(int) |
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get_byte (j_decompress_ptr cinfo) |
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/* Read next input byte; we do not support suspension in this module. */ |
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{ |
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struct jpeg_source_mgr * src = cinfo->src; |
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if (src->bytes_in_buffer == 0) |
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if (! (*src->fill_input_buffer) (cinfo)) |
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ERREXIT(cinfo, JERR_CANT_SUSPEND); |
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src->bytes_in_buffer--; |
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return GETJOCTET(*src->next_input_byte++); |
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} |
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/* |
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* The core arithmetic decoding routine (common in JPEG and JBIG). |
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* This needs to go as fast as possible. |
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* Machine-dependent optimization facilities |
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* are not utilized in this portable implementation. |
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* However, this code should be fairly efficient and |
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* may be a good base for further optimizations anyway. |
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* |
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* Return value is 0 or 1 (binary decision). |
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* |
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* Note: I've changed the handling of the code base & bit |
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* buffer register C compared to other implementations |
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* based on the standards layout & procedures. |
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* While it also contains both the actual base of the |
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* coding interval (16 bits) and the next-bits buffer, |
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* the cut-point between these two parts is floating |
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* (instead of fixed) with the bit shift counter CT. |
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* Thus, we also need only one (variable instead of |
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* fixed size) shift for the LPS/MPS decision, and |
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* we can get away with any renormalization update |
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* of C (except for new data insertion, of course). |
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* |
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* I've also introduced a new scheme for accessing |
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* the probability estimation state machine table, |
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* derived from Markus Kuhn's JBIG implementation. |
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*/ |
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LOCAL(int) |
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arith_decode (j_decompress_ptr cinfo, unsigned char *st) |
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{ |
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register arith_entropy_ptr e = (arith_entropy_ptr) cinfo->entropy; |
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register unsigned char nl, nm; |
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register INT32 qe, temp; |
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register int sv, data; |
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/* Renormalization & data input per section D.2.6 */ |
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while (e->a < 0x8000L) { |
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if (--e->ct < 0) { |
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/* Need to fetch next data byte */ |
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if (cinfo->unread_marker) |
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data = 0; /* stuff zero data */ |
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else { |
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data = get_byte(cinfo); /* read next input byte */ |
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if (data == 0xFF) { /* zero stuff or marker code */ |
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do data = get_byte(cinfo); |
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while (data == 0xFF); /* swallow extra 0xFF bytes */ |
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if (data == 0) |
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data = 0xFF; /* discard stuffed zero byte */ |
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else { |
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/* Note: Different from the Huffman decoder, hitting |
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* a marker while processing the compressed data |
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* segment is legal in arithmetic coding. |
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* The convention is to supply zero data |
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* then until decoding is complete. |
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*/ |
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cinfo->unread_marker = data; |
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data = 0; |
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} |
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} |
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} |
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e->c = (e->c << 8) | data; /* insert data into C register */ |
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if ((e->ct += 8) < 0) /* update bit shift counter */ |
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/* Need more initial bytes */ |
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if (++e->ct == 0) |
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/* Got 2 initial bytes -> re-init A and exit loop */ |
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e->a = 0x8000L; /* => e->a = 0x10000L after loop exit */ |
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} |
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e->a <<= 1; |
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} |
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/* Fetch values from our compact representation of Table D.3(D.2): |
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* Qe values and probability estimation state machine |
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*/ |
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sv = *st; |
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qe = jpeg_aritab[sv & 0x7F]; /* => Qe_Value */ |
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nl = qe & 0xFF; qe >>= 8; /* Next_Index_LPS + Switch_MPS */ |
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nm = qe & 0xFF; qe >>= 8; /* Next_Index_MPS */ |
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/* Decode & estimation procedures per sections D.2.4 & D.2.5 */ |
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temp = e->a - qe; |
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e->a = temp; |
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temp <<= e->ct; |
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if (e->c >= temp) { |
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e->c -= temp; |
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/* Conditional LPS (less probable symbol) exchange */ |
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if (e->a < qe) { |
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e->a = qe; |
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*st = (sv & 0x80) ^ nm; /* Estimate_after_MPS */ |
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} else { |
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e->a = qe; |
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*st = (sv & 0x80) ^ nl; /* Estimate_after_LPS */ |
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sv ^= 0x80; /* Exchange LPS/MPS */ |
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} |
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} else if (e->a < 0x8000L) { |
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/* Conditional MPS (more probable symbol) exchange */ |
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if (e->a < qe) { |
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*st = (sv & 0x80) ^ nl; /* Estimate_after_LPS */ |
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sv ^= 0x80; /* Exchange LPS/MPS */ |
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} else { |
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*st = (sv & 0x80) ^ nm; /* Estimate_after_MPS */ |
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} |
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} |
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return sv >> 7; |
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} |
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/* |
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* Check for a restart marker & resynchronize decoder. |
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*/ |
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LOCAL(void) |
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process_restart (j_decompress_ptr cinfo) |
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{ |
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arith_entropy_ptr entropy = (arith_entropy_ptr) cinfo->entropy; |
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int ci; |
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jpeg_component_info * compptr; |
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/* Advance past the RSTn marker */ |
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if (! (*cinfo->marker->read_restart_marker) (cinfo)) |
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ERREXIT(cinfo, JERR_CANT_SUSPEND); |
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/* Re-initialize statistics areas */ |
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for (ci = 0; ci < cinfo->comps_in_scan; ci++) { |
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compptr = cinfo->cur_comp_info[ci]; |
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if (! cinfo->progressive_mode || (cinfo->Ss == 0 && cinfo->Ah == 0)) { |
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MEMZERO(entropy->dc_stats[compptr->dc_tbl_no], DC_STAT_BINS); |
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/* Reset DC predictions to 0 */ |
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entropy->last_dc_val[ci] = 0; |
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entropy->dc_context[ci] = 0; |
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} |
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if ((! cinfo->progressive_mode && cinfo->lim_Se) || |
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(cinfo->progressive_mode && cinfo->Ss)) { |
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MEMZERO(entropy->ac_stats[compptr->ac_tbl_no], AC_STAT_BINS); |
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} |
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} |
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/* Reset arithmetic decoding variables */ |
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entropy->c = 0; |
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entropy->a = 0; |
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entropy->ct = -16; /* force reading 2 initial bytes to fill C */ |
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/* Reset restart counter */ |
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entropy->restarts_to_go = cinfo->restart_interval; |
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} |
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/* |
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* Arithmetic MCU decoding. |
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* Each of these routines decodes and returns one MCU's worth of |
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* arithmetic-compressed coefficients. |
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* The coefficients are reordered from zigzag order into natural array order, |
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* but are not dequantized. |
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* |
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* The i'th block of the MCU is stored into the block pointed to by |
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* MCU_data[i]. WE ASSUME THIS AREA IS INITIALLY ZEROED BY THE CALLER. |
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*/ |
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/* |
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* MCU decoding for DC initial scan (either spectral selection, |
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* or first pass of successive approximation). |
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*/ |
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METHODDEF(boolean) |
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decode_mcu_DC_first (j_decompress_ptr cinfo, JBLOCKROW *MCU_data) |
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{ |
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arith_entropy_ptr entropy = (arith_entropy_ptr) cinfo->entropy; |
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JBLOCKROW block; |
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unsigned char *st; |
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int blkn, ci, tbl, sign; |
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int v, m; |
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/* Process restart marker if needed */ |
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if (cinfo->restart_interval) { |
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if (entropy->restarts_to_go == 0) |
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process_restart(cinfo); |
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entropy->restarts_to_go--; |
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} |
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if (entropy->ct == -1) return TRUE; /* if error do nothing */ |
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/* Outer loop handles each block in the MCU */ |
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for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) { |
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block = MCU_data[blkn]; |
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ci = cinfo->MCU_membership[blkn]; |
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tbl = cinfo->cur_comp_info[ci]->dc_tbl_no; |
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/* Sections F.2.4.1 & F.1.4.4.1: Decoding of DC coefficients */ |
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/* Table F.4: Point to statistics bin S0 for DC coefficient coding */ |
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st = entropy->dc_stats[tbl] + entropy->dc_context[ci]; |
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/* Figure F.19: Decode_DC_DIFF */ |
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if (arith_decode(cinfo, st) == 0) |
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entropy->dc_context[ci] = 0; |
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else { |
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/* Figure F.21: Decoding nonzero value v */ |
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/* Figure F.22: Decoding the sign of v */ |
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sign = arith_decode(cinfo, st + 1); |
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st += 2; st += sign; |
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/* Figure F.23: Decoding the magnitude category of v */ |
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if ((m = arith_decode(cinfo, st)) != 0) { |
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st = entropy->dc_stats[tbl] + 20; /* Table F.4: X1 = 20 */ |
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while (arith_decode(cinfo, st)) { |
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if ((m <<= 1) == 0x8000) { |
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WARNMS(cinfo, JWRN_ARITH_BAD_CODE); |
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entropy->ct = -1; /* magnitude overflow */ |
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return TRUE; |
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} |
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st += 1; |
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} |
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} |
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/* Section F.1.4.4.1.2: Establish dc_context conditioning category */ |
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if (m < (int) ((1L << cinfo->arith_dc_L[tbl]) >> 1)) |
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entropy->dc_context[ci] = 0; /* zero diff category */ |
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else if (m > (int) ((1L << cinfo->arith_dc_U[tbl]) >> 1)) |
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entropy->dc_context[ci] = 12 + (sign * 4); /* large diff category */ |
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else |
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entropy->dc_context[ci] = 4 + (sign * 4); /* small diff category */ |
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v = m; |
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/* Figure F.24: Decoding the magnitude bit pattern of v */ |
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st += 14; |
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while (m >>= 1) |
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if (arith_decode(cinfo, st)) v |= m; |
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v += 1; if (sign) v = -v; |
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entropy->last_dc_val[ci] += v; |
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} |
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/* Scale and output the DC coefficient (assumes jpeg_natural_order[0]=0) */ |
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(*block)[0] = (JCOEF) (entropy->last_dc_val[ci] << cinfo->Al); |
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} |
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return TRUE; |
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} |
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/* |
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* MCU decoding for AC initial scan (either spectral selection, |
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* or first pass of successive approximation). |
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*/ |
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METHODDEF(boolean) |
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decode_mcu_AC_first (j_decompress_ptr cinfo, JBLOCKROW *MCU_data) |
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{ |
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arith_entropy_ptr entropy = (arith_entropy_ptr) cinfo->entropy; |
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JBLOCKROW block; |
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unsigned char *st; |
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int tbl, sign, k; |
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int v, m; |
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const int * natural_order; |
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/* Process restart marker if needed */ |
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if (cinfo->restart_interval) { |
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if (entropy->restarts_to_go == 0) |
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process_restart(cinfo); |
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entropy->restarts_to_go--; |
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} |
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if (entropy->ct == -1) return TRUE; /* if error do nothing */ |
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natural_order = cinfo->natural_order; |
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/* There is always only one block per MCU */ |
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block = MCU_data[0]; |
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tbl = cinfo->cur_comp_info[0]->ac_tbl_no; |
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/* Sections F.2.4.2 & F.1.4.4.2: Decoding of AC coefficients */ |
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/* Figure F.20: Decode_AC_coefficients */ |
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for (k = cinfo->Ss; k <= cinfo->Se; k++) { |
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st = entropy->ac_stats[tbl] + 3 * (k - 1); |
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if (arith_decode(cinfo, st)) break; /* EOB flag */ |
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while (arith_decode(cinfo, st + 1) == 0) { |
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st += 3; k++; |
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if (k > cinfo->Se) { |
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WARNMS(cinfo, JWRN_ARITH_BAD_CODE); |
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entropy->ct = -1; /* spectral overflow */ |
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return TRUE; |
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} |
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} |
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/* Figure F.21: Decoding nonzero value v */ |
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/* Figure F.22: Decoding the sign of v */ |
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sign = arith_decode(cinfo, entropy->fixed_bin); |
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st += 2; |
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/* Figure F.23: Decoding the magnitude category of v */ |
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if ((m = arith_decode(cinfo, st)) != 0) { |
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if (arith_decode(cinfo, st)) { |
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m <<= 1; |
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st = entropy->ac_stats[tbl] + |
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(k <= cinfo->arith_ac_K[tbl] ? 189 : 217); |
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while (arith_decode(cinfo, st)) { |
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if ((m <<= 1) == 0x8000) { |
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WARNMS(cinfo, JWRN_ARITH_BAD_CODE); |
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entropy->ct = -1; /* magnitude overflow */ |
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return TRUE; |
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} |
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st += 1; |
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} |
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} |
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} |
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v = m; |
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/* Figure F.24: Decoding the magnitude bit pattern of v */ |
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st += 14; |
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while (m >>= 1) |
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if (arith_decode(cinfo, st)) v |= m; |
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v += 1; if (sign) v = -v; |
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/* Scale and output coefficient in natural (dezigzagged) order */ |
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(*block)[natural_order[k]] = (JCOEF) (v << cinfo->Al); |
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} |
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return TRUE; |
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} |
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/* |
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* MCU decoding for DC successive approximation refinement scan. |
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*/ |
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METHODDEF(boolean) |
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decode_mcu_DC_refine (j_decompress_ptr cinfo, JBLOCKROW *MCU_data) |
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{ |
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arith_entropy_ptr entropy = (arith_entropy_ptr) cinfo->entropy; |
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unsigned char *st; |
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int p1, blkn; |
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/* Process restart marker if needed */ |
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if (cinfo->restart_interval) { |
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if (entropy->restarts_to_go == 0) |
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process_restart(cinfo); |
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entropy->restarts_to_go--; |
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} |
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st = entropy->fixed_bin; /* use fixed probability estimation */ |
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p1 = 1 << cinfo->Al; /* 1 in the bit position being coded */ |
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/* Outer loop handles each block in the MCU */ |
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for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) { |
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/* Encoded data is simply the next bit of the two's-complement DC value */ |
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if (arith_decode(cinfo, st)) |
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MCU_data[blkn][0][0] |= p1; |
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} |
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return TRUE; |
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} |
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/* |
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* MCU decoding for AC successive approximation refinement scan. |
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*/ |
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METHODDEF(boolean) |
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decode_mcu_AC_refine (j_decompress_ptr cinfo, JBLOCKROW *MCU_data) |
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{ |
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arith_entropy_ptr entropy = (arith_entropy_ptr) cinfo->entropy; |
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JBLOCKROW block; |
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JCOEFPTR thiscoef; |
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unsigned char *st; |
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int tbl, k, kex; |
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int p1, m1; |
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const int * natural_order; |
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/* Process restart marker if needed */ |
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if (cinfo->restart_interval) { |
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if (entropy->restarts_to_go == 0) |
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process_restart(cinfo); |
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entropy->restarts_to_go--; |
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} |
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if (entropy->ct == -1) return TRUE; /* if error do nothing */ |
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natural_order = cinfo->natural_order; |
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/* There is always only one block per MCU */ |
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block = MCU_data[0]; |
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tbl = cinfo->cur_comp_info[0]->ac_tbl_no; |
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p1 = 1 << cinfo->Al; /* 1 in the bit position being coded */ |
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m1 = (-1) << cinfo->Al; /* -1 in the bit position being coded */ |
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/* Establish EOBx (previous stage end-of-block) index */ |
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for (kex = cinfo->Se; kex > 0; kex--) |
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if ((*block)[natural_order[kex]]) break; |
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for (k = cinfo->Ss; k <= cinfo->Se; k++) { |
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st = entropy->ac_stats[tbl] + 3 * (k - 1); |
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if (k > kex) |
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if (arith_decode(cinfo, st)) break; /* EOB flag */ |
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for (;;) { |
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thiscoef = *block + natural_order[k]; |
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if (*thiscoef) { /* previously nonzero coef */ |
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if (arith_decode(cinfo, st + 2)) { |
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if (*thiscoef < 0) |
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*thiscoef += m1; |
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else |
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*thiscoef += p1; |
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} |
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break; |
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} |
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if (arith_decode(cinfo, st + 1)) { /* newly nonzero coef */ |
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if (arith_decode(cinfo, entropy->fixed_bin)) |
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*thiscoef = m1; |
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else |
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*thiscoef = p1; |
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break; |
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} |
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st += 3; k++; |
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if (k > cinfo->Se) { |
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WARNMS(cinfo, JWRN_ARITH_BAD_CODE); |
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entropy->ct = -1; /* spectral overflow */ |
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return TRUE; |
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} |
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} |
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} |
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return TRUE; |
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} |
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/* |
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* Decode one MCU's worth of arithmetic-compressed coefficients. |
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*/ |
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METHODDEF(boolean) |
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decode_mcu (j_decompress_ptr cinfo, JBLOCKROW *MCU_data) |
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{ |
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arith_entropy_ptr entropy = (arith_entropy_ptr) cinfo->entropy; |
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jpeg_component_info * compptr; |
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JBLOCKROW block; |
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unsigned char *st; |
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int blkn, ci, tbl, sign, k; |
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int v, m; |
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const int * natural_order; |
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/* Process restart marker if needed */ |
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if (cinfo->restart_interval) { |
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if (entropy->restarts_to_go == 0) |
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process_restart(cinfo); |
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entropy->restarts_to_go--; |
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} |
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if (entropy->ct == -1) return TRUE; /* if error do nothing */ |
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natural_order = cinfo->natural_order; |
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/* Outer loop handles each block in the MCU */ |
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for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) { |
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block = MCU_data[blkn]; |
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ci = cinfo->MCU_membership[blkn]; |
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compptr = cinfo->cur_comp_info[ci]; |
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|
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/* Sections F.2.4.1 & F.1.4.4.1: Decoding of DC coefficients */ |
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tbl = compptr->dc_tbl_no; |
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|
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/* Table F.4: Point to statistics bin S0 for DC coefficient coding */ |
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st = entropy->dc_stats[tbl] + entropy->dc_context[ci]; |
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|
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/* Figure F.19: Decode_DC_DIFF */ |
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if (arith_decode(cinfo, st) == 0) |
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entropy->dc_context[ci] = 0; |
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else { |
|
/* Figure F.21: Decoding nonzero value v */ |
|
/* Figure F.22: Decoding the sign of v */ |
|
sign = arith_decode(cinfo, st + 1); |
|
st += 2; st += sign; |
|
/* Figure F.23: Decoding the magnitude category of v */ |
|
if ((m = arith_decode(cinfo, st)) != 0) { |
|
st = entropy->dc_stats[tbl] + 20; /* Table F.4: X1 = 20 */ |
|
while (arith_decode(cinfo, st)) { |
|
if ((m <<= 1) == 0x8000) { |
|
WARNMS(cinfo, JWRN_ARITH_BAD_CODE); |
|
entropy->ct = -1; /* magnitude overflow */ |
|
return TRUE; |
|
} |
|
st += 1; |
|
} |
|
} |
|
/* Section F.1.4.4.1.2: Establish dc_context conditioning category */ |
|
if (m < (int) ((1L << cinfo->arith_dc_L[tbl]) >> 1)) |
|
entropy->dc_context[ci] = 0; /* zero diff category */ |
|
else if (m > (int) ((1L << cinfo->arith_dc_U[tbl]) >> 1)) |
|
entropy->dc_context[ci] = 12 + (sign * 4); /* large diff category */ |
|
else |
|
entropy->dc_context[ci] = 4 + (sign * 4); /* small diff category */ |
|
v = m; |
|
/* Figure F.24: Decoding the magnitude bit pattern of v */ |
|
st += 14; |
|
while (m >>= 1) |
|
if (arith_decode(cinfo, st)) v |= m; |
|
v += 1; if (sign) v = -v; |
|
entropy->last_dc_val[ci] += v; |
|
} |
|
|
|
(*block)[0] = (JCOEF) entropy->last_dc_val[ci]; |
|
|
|
/* Sections F.2.4.2 & F.1.4.4.2: Decoding of AC coefficients */ |
|
|
|
if (cinfo->lim_Se == 0) continue; |
|
tbl = compptr->ac_tbl_no; |
|
k = 0; |
|
|
|
/* Figure F.20: Decode_AC_coefficients */ |
|
do { |
|
st = entropy->ac_stats[tbl] + 3 * k; |
|
if (arith_decode(cinfo, st)) break; /* EOB flag */ |
|
for (;;) { |
|
k++; |
|
if (arith_decode(cinfo, st + 1)) break; |
|
st += 3; |
|
if (k >= cinfo->lim_Se) { |
|
WARNMS(cinfo, JWRN_ARITH_BAD_CODE); |
|
entropy->ct = -1; /* spectral overflow */ |
|
return TRUE; |
|
} |
|
} |
|
/* Figure F.21: Decoding nonzero value v */ |
|
/* Figure F.22: Decoding the sign of v */ |
|
sign = arith_decode(cinfo, entropy->fixed_bin); |
|
st += 2; |
|
/* Figure F.23: Decoding the magnitude category of v */ |
|
if ((m = arith_decode(cinfo, st)) != 0) { |
|
if (arith_decode(cinfo, st)) { |
|
m <<= 1; |
|
st = entropy->ac_stats[tbl] + |
|
(k <= cinfo->arith_ac_K[tbl] ? 189 : 217); |
|
while (arith_decode(cinfo, st)) { |
|
if ((m <<= 1) == 0x8000) { |
|
WARNMS(cinfo, JWRN_ARITH_BAD_CODE); |
|
entropy->ct = -1; /* magnitude overflow */ |
|
return TRUE; |
|
} |
|
st += 1; |
|
} |
|
} |
|
} |
|
v = m; |
|
/* Figure F.24: Decoding the magnitude bit pattern of v */ |
|
st += 14; |
|
while (m >>= 1) |
|
if (arith_decode(cinfo, st)) v |= m; |
|
v += 1; if (sign) v = -v; |
|
(*block)[natural_order[k]] = (JCOEF) v; |
|
} while (k < cinfo->lim_Se); |
|
} |
|
|
|
return TRUE; |
|
} |
|
|
|
|
|
/* |
|
* Initialize for an arithmetic-compressed scan. |
|
*/ |
|
|
|
METHODDEF(void) |
|
start_pass (j_decompress_ptr cinfo) |
|
{ |
|
arith_entropy_ptr entropy = (arith_entropy_ptr) cinfo->entropy; |
|
int ci, tbl; |
|
jpeg_component_info * compptr; |
|
|
|
if (cinfo->progressive_mode) { |
|
/* Validate progressive scan parameters */ |
|
if (cinfo->Ss == 0) { |
|
if (cinfo->Se != 0) |
|
goto bad; |
|
} else { |
|
/* need not check Ss/Se < 0 since they came from unsigned bytes */ |
|
if (cinfo->Se < cinfo->Ss || cinfo->Se > cinfo->lim_Se) |
|
goto bad; |
|
/* AC scans may have only one component */ |
|
if (cinfo->comps_in_scan != 1) |
|
goto bad; |
|
} |
|
if (cinfo->Ah != 0) { |
|
/* Successive approximation refinement scan: must have Al = Ah-1. */ |
|
if (cinfo->Ah-1 != cinfo->Al) |
|
goto bad; |
|
} |
|
if (cinfo->Al > 13) { /* need not check for < 0 */ |
|
bad: |
|
ERREXIT4(cinfo, JERR_BAD_PROGRESSION, |
|
cinfo->Ss, cinfo->Se, cinfo->Ah, cinfo->Al); |
|
} |
|
/* Update progression status, and verify that scan order is legal. |
|
* Note that inter-scan inconsistencies are treated as warnings |
|
* not fatal errors ... not clear if this is right way to behave. |
|
*/ |
|
for (ci = 0; ci < cinfo->comps_in_scan; ci++) { |
|
int coefi, cindex = cinfo->cur_comp_info[ci]->component_index; |
|
int *coef_bit_ptr = & cinfo->coef_bits[cindex][0]; |
|
if (cinfo->Ss && coef_bit_ptr[0] < 0) /* AC without prior DC scan */ |
|
WARNMS2(cinfo, JWRN_BOGUS_PROGRESSION, cindex, 0); |
|
for (coefi = cinfo->Ss; coefi <= cinfo->Se; coefi++) { |
|
int expected = (coef_bit_ptr[coefi] < 0) ? 0 : coef_bit_ptr[coefi]; |
|
if (cinfo->Ah != expected) |
|
WARNMS2(cinfo, JWRN_BOGUS_PROGRESSION, cindex, coefi); |
|
coef_bit_ptr[coefi] = cinfo->Al; |
|
} |
|
} |
|
/* Select MCU decoding routine */ |
|
if (cinfo->Ah == 0) { |
|
if (cinfo->Ss == 0) |
|
entropy->pub.decode_mcu = decode_mcu_DC_first; |
|
else |
|
entropy->pub.decode_mcu = decode_mcu_AC_first; |
|
} else { |
|
if (cinfo->Ss == 0) |
|
entropy->pub.decode_mcu = decode_mcu_DC_refine; |
|
else |
|
entropy->pub.decode_mcu = decode_mcu_AC_refine; |
|
} |
|
} else { |
|
/* Check that the scan parameters Ss, Se, Ah/Al are OK for sequential JPEG. |
|
* This ought to be an error condition, but we make it a warning. |
|
*/ |
|
if (cinfo->Ss != 0 || cinfo->Ah != 0 || cinfo->Al != 0 || |
|
(cinfo->Se < DCTSIZE2 && cinfo->Se != cinfo->lim_Se)) |
|
WARNMS(cinfo, JWRN_NOT_SEQUENTIAL); |
|
/* Select MCU decoding routine */ |
|
entropy->pub.decode_mcu = decode_mcu; |
|
} |
|
|
|
/* Allocate & initialize requested statistics areas */ |
|
for (ci = 0; ci < cinfo->comps_in_scan; ci++) { |
|
compptr = cinfo->cur_comp_info[ci]; |
|
if (! cinfo->progressive_mode || (cinfo->Ss == 0 && cinfo->Ah == 0)) { |
|
tbl = compptr->dc_tbl_no; |
|
if (tbl < 0 || tbl >= NUM_ARITH_TBLS) |
|
ERREXIT1(cinfo, JERR_NO_ARITH_TABLE, tbl); |
|
if (entropy->dc_stats[tbl] == NULL) |
|
entropy->dc_stats[tbl] = (unsigned char *) (*cinfo->mem->alloc_small) |
|
((j_common_ptr) cinfo, JPOOL_IMAGE, DC_STAT_BINS); |
|
MEMZERO(entropy->dc_stats[tbl], DC_STAT_BINS); |
|
/* Initialize DC predictions to 0 */ |
|
entropy->last_dc_val[ci] = 0; |
|
entropy->dc_context[ci] = 0; |
|
} |
|
if ((! cinfo->progressive_mode && cinfo->lim_Se) || |
|
(cinfo->progressive_mode && cinfo->Ss)) { |
|
tbl = compptr->ac_tbl_no; |
|
if (tbl < 0 || tbl >= NUM_ARITH_TBLS) |
|
ERREXIT1(cinfo, JERR_NO_ARITH_TABLE, tbl); |
|
if (entropy->ac_stats[tbl] == NULL) |
|
entropy->ac_stats[tbl] = (unsigned char *) (*cinfo->mem->alloc_small) |
|
((j_common_ptr) cinfo, JPOOL_IMAGE, AC_STAT_BINS); |
|
MEMZERO(entropy->ac_stats[tbl], AC_STAT_BINS); |
|
} |
|
} |
|
|
|
/* Initialize arithmetic decoding variables */ |
|
entropy->c = 0; |
|
entropy->a = 0; |
|
entropy->ct = -16; /* force reading 2 initial bytes to fill C */ |
|
|
|
/* Initialize restart counter */ |
|
entropy->restarts_to_go = cinfo->restart_interval; |
|
} |
|
|
|
|
|
/* |
|
* Module initialization routine for arithmetic entropy decoding. |
|
*/ |
|
|
|
GLOBAL(void) |
|
jinit_arith_decoder (j_decompress_ptr cinfo) |
|
{ |
|
arith_entropy_ptr entropy; |
|
int i; |
|
|
|
entropy = (arith_entropy_ptr) |
|
(*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, |
|
SIZEOF(arith_entropy_decoder)); |
|
cinfo->entropy = (struct jpeg_entropy_decoder *) entropy; |
|
entropy->pub.start_pass = start_pass; |
|
|
|
/* Mark tables unallocated */ |
|
for (i = 0; i < NUM_ARITH_TBLS; i++) { |
|
entropy->dc_stats[i] = NULL; |
|
entropy->ac_stats[i] = NULL; |
|
} |
|
|
|
/* Initialize index for fixed probability estimation */ |
|
entropy->fixed_bin[0] = 113; |
|
|
|
if (cinfo->progressive_mode) { |
|
/* Create progression status table */ |
|
int *coef_bit_ptr, ci; |
|
cinfo->coef_bits = (int (*)[DCTSIZE2]) |
|
(*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, |
|
cinfo->num_components*DCTSIZE2*SIZEOF(int)); |
|
coef_bit_ptr = & cinfo->coef_bits[0][0]; |
|
for (ci = 0; ci < cinfo->num_components; ci++) |
|
for (i = 0; i < DCTSIZE2; i++) |
|
*coef_bit_ptr++ = -1; |
|
} |
|
}
|
|
|