Doxygen Source Code Documentation
jdhuff.c File Reference
#include "jinclude.h"
#include "jpeglib.h"
#include "jdhuff.h"
Go to the source code of this file.
Data Structures | |
struct | huff_entropy_decoder |
struct | savable_state |
Defines | |
#define | JPEG_INTERNALS |
#define | ASSIGN_STATE(dest, src) ((dest) = (src)) |
#define | MIN_GET_BITS (BIT_BUF_SIZE-7) |
#define | HUFF_EXTEND(x, s) ((x) < extend_test[s] ? (x) + extend_offset[s] : (x)) |
Typedefs | |
typedef huff_entropy_decoder * | huff_entropy_ptr |
Functions | |
start_pass_huff_decoder (j_decompress_ptr cinfo) | |
jpeg_make_d_derived_tbl (j_decompress_ptr cinfo, boolean isDC, int tblno, d_derived_tbl **pdtbl) | |
jpeg_fill_bit_buffer (bitread_working_state *state, register bit_buf_type get_buffer, register int bits_left, int nbits) | |
jpeg_huff_decode (bitread_working_state *state, register bit_buf_type get_buffer, register int bits_left, d_derived_tbl *htbl, int min_bits) | |
process_restart (j_decompress_ptr cinfo) | |
decode_mcu (j_decompress_ptr cinfo, JBLOCKROW *MCU_data) | |
jinit_huff_decoder (j_decompress_ptr cinfo) | |
Variables | |
const int | extend_test [16] |
const int | extend_offset [16] |
Define Documentation
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Definition at line 447 of file jdhuff.c. Referenced by decode_mcu(), decode_mcu_AC_first(), and decode_mcu_DC_first(). |
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Definition at line 287 of file jdhuff.c. Referenced by jpeg_fill_bit_buffer(). |
Typedef Documentation
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Function Documentation
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Definition at line 517 of file jdhuff.c. References huff_entropy_decoder::ac_cur_tbls, huff_entropy_decoder::ac_needed, ASSIGN_STATE, BITREAD_LOAD_STATE, BITREAD_SAVE_STATE, BITREAD_STATE_VARS, huff_entropy_decoder::bitstate, jpeg_decompress_struct::blocks_in_MCU, CHECK_BIT_BUFFER, huff_entropy_decoder::dc_cur_tbls, huff_entropy_decoder::dc_needed, DROP_BITS, jpeg_decompress_struct::entropy, GET_BITS, HUFF_DECODE, HUFF_EXTEND, jpeg_entropy_decoder::insufficient_data, JBLOCKROW, savable_state::last_dc_val, jpeg_decompress_struct::MCU_membership, process_restart(), huff_entropy_decoder::pub, r, jpeg_decompress_struct::restart_interval, huff_entropy_decoder::restarts_to_go, and huff_entropy_decoder::saved. Referenced by jinit_huff_decoder().
00518 { 00519 huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy; 00520 int blkn; 00521 BITREAD_STATE_VARS; 00522 savable_state state; 00523 00524 /* Process restart marker if needed; may have to suspend */ 00525 if (cinfo->restart_interval) { 00526 if (entropy->restarts_to_go == 0) 00527 if (! process_restart(cinfo)) 00528 return FALSE; 00529 } 00530 00531 /* If we've run out of data, just leave the MCU set to zeroes. 00532 * This way, we return uniform gray for the remainder of the segment. 00533 */ 00534 if (! entropy->pub.insufficient_data) { 00535 00536 /* Load up working state */ 00537 BITREAD_LOAD_STATE(cinfo,entropy->bitstate); 00538 ASSIGN_STATE(state, entropy->saved); 00539 00540 /* Outer loop handles each block in the MCU */ 00541 00542 for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) { 00543 JBLOCKROW block = MCU_data[blkn]; 00544 d_derived_tbl * dctbl = entropy->dc_cur_tbls[blkn]; 00545 d_derived_tbl * actbl = entropy->ac_cur_tbls[blkn]; 00546 register int s, k, r; 00547 00548 /* Decode a single block's worth of coefficients */ 00549 00550 /* Section F.2.2.1: decode the DC coefficient difference */ 00551 HUFF_DECODE(s, br_state, dctbl, return FALSE, label1); 00552 if (s) { 00553 CHECK_BIT_BUFFER(br_state, s, return FALSE); 00554 r = GET_BITS(s); 00555 s = HUFF_EXTEND(r, s); 00556 } 00557 00558 if (entropy->dc_needed[blkn]) { 00559 /* Convert DC difference to actual value, update last_dc_val */ 00560 int ci = cinfo->MCU_membership[blkn]; 00561 s += state.last_dc_val[ci]; 00562 state.last_dc_val[ci] = s; 00563 /* Output the DC coefficient (assumes jpeg_natural_order[0] = 0) */ 00564 (*block)[0] = (JCOEF) s; 00565 } 00566 00567 if (entropy->ac_needed[blkn]) { 00568 00569 /* Section F.2.2.2: decode the AC coefficients */ 00570 /* Since zeroes are skipped, output area must be cleared beforehand */ 00571 for (k = 1; k < DCTSIZE2; k++) { 00572 HUFF_DECODE(s, br_state, actbl, return FALSE, label2); 00573 00574 r = s >> 4; 00575 s &= 15; 00576 00577 if (s) { 00578 k += r; 00579 CHECK_BIT_BUFFER(br_state, s, return FALSE); 00580 r = GET_BITS(s); 00581 s = HUFF_EXTEND(r, s); 00582 /* Output coefficient in natural (dezigzagged) order. 00583 * Note: the extra entries in jpeg_natural_order[] will save us 00584 * if k >= DCTSIZE2, which could happen if the data is corrupted. 00585 */ 00586 (*block)[jpeg_natural_order[k]] = (JCOEF) s; 00587 } else { 00588 if (r != 15) 00589 break; 00590 k += 15; 00591 } 00592 } 00593 00594 } else { 00595 00596 /* Section F.2.2.2: decode the AC coefficients */ 00597 /* In this path we just discard the values */ 00598 for (k = 1; k < DCTSIZE2; k++) { 00599 HUFF_DECODE(s, br_state, actbl, return FALSE, label3); 00600 00601 r = s >> 4; 00602 s &= 15; 00603 00604 if (s) { 00605 k += r; 00606 CHECK_BIT_BUFFER(br_state, s, return FALSE); 00607 DROP_BITS(s); 00608 } else { 00609 if (r != 15) 00610 break; 00611 k += 15; 00612 } 00613 } 00614 00615 } 00616 } 00617 00618 /* Completed MCU, so update state */ 00619 BITREAD_SAVE_STATE(cinfo,entropy->bitstate); 00620 ASSIGN_STATE(entropy->saved, state); 00621 } 00622 00623 /* Account for restart interval (no-op if not using restarts) */ 00624 entropy->restarts_to_go--; 00625 00626 return TRUE; 00627 } |
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Definition at line 635 of file jdhuff.c. References decode_mcu(), i, JPOOL_IMAGE, NUM_HUFF_TBLS, SIZEOF, and start_pass_huff_decoder(). Referenced by master_selection(), and transdecode_master_selection().
00636 { 00637 huff_entropy_ptr entropy; 00638 int i; 00639 00640 entropy = (huff_entropy_ptr) 00641 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, 00642 SIZEOF(huff_entropy_decoder)); 00643 cinfo->entropy = (struct jpeg_entropy_decoder *) entropy; 00644 entropy->pub.start_pass = start_pass_huff_decoder; 00645 entropy->pub.decode_mcu = decode_mcu; 00646 00647 /* Mark tables unallocated */ 00648 for (i = 0; i < NUM_HUFF_TBLS; i++) { 00649 entropy->dc_derived_tbls[i] = entropy->ac_derived_tbls[i] = NULL; 00650 } 00651 } |
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Definition at line 292 of file jdhuff.c. References bit_buf_type, bitread_working_state::bits_left, bits_left, jpeg_source_mgr::bytes_in_buffer, bitread_working_state::bytes_in_buffer, c, bitread_working_state::cinfo, jpeg_decompress_struct::entropy, bitread_working_state::get_buffer, get_buffer, GETJOCTET, jpeg_entropy_decoder::insufficient_data, JOCTET, MIN_GET_BITS, jpeg_source_mgr::next_input_byte, bitread_working_state::next_input_byte, jpeg_decompress_struct::src, jpeg_decompress_struct::unread_marker, and WARNMS.
00296 { 00297 /* Copy heavily used state fields into locals (hopefully registers) */ 00298 register const JOCTET * next_input_byte = state->next_input_byte; 00299 register size_t bytes_in_buffer = state->bytes_in_buffer; 00300 j_decompress_ptr cinfo = state->cinfo; 00301 00302 /* Attempt to load at least MIN_GET_BITS bits into get_buffer. */ 00303 /* (It is assumed that no request will be for more than that many bits.) */ 00304 /* We fail to do so only if we hit a marker or are forced to suspend. */ 00305 00306 if (cinfo->unread_marker == 0) { /* cannot advance past a marker */ 00307 while (bits_left < MIN_GET_BITS) { 00308 register int c; 00309 00310 /* Attempt to read a byte */ 00311 if (bytes_in_buffer == 0) { 00312 if (! (*cinfo->src->fill_input_buffer) (cinfo)) 00313 return FALSE; 00314 next_input_byte = cinfo->src->next_input_byte; 00315 bytes_in_buffer = cinfo->src->bytes_in_buffer; 00316 } 00317 bytes_in_buffer--; 00318 c = GETJOCTET(*next_input_byte++); 00319 00320 /* If it's 0xFF, check and discard stuffed zero byte */ 00321 if (c == 0xFF) { 00322 /* Loop here to discard any padding FF's on terminating marker, 00323 * so that we can save a valid unread_marker value. NOTE: we will 00324 * accept multiple FF's followed by a 0 as meaning a single FF data 00325 * byte. This data pattern is not valid according to the standard. 00326 */ 00327 do { 00328 if (bytes_in_buffer == 0) { 00329 if (! (*cinfo->src->fill_input_buffer) (cinfo)) 00330 return FALSE; 00331 next_input_byte = cinfo->src->next_input_byte; 00332 bytes_in_buffer = cinfo->src->bytes_in_buffer; 00333 } 00334 bytes_in_buffer--; 00335 c = GETJOCTET(*next_input_byte++); 00336 } while (c == 0xFF); 00337 00338 if (c == 0) { 00339 /* Found FF/00, which represents an FF data byte */ 00340 c = 0xFF; 00341 } else { 00342 /* Oops, it's actually a marker indicating end of compressed data. 00343 * Save the marker code for later use. 00344 * Fine point: it might appear that we should save the marker into 00345 * bitread working state, not straight into permanent state. But 00346 * once we have hit a marker, we cannot need to suspend within the 00347 * current MCU, because we will read no more bytes from the data 00348 * source. So it is OK to update permanent state right away. 00349 */ 00350 cinfo->unread_marker = c; 00351 /* See if we need to insert some fake zero bits. */ 00352 goto no_more_bytes; 00353 } 00354 } 00355 00356 /* OK, load c into get_buffer */ 00357 get_buffer = (get_buffer << 8) | c; 00358 bits_left += 8; 00359 } /* end while */ 00360 } else { 00361 no_more_bytes: 00362 /* We get here if we've read the marker that terminates the compressed 00363 * data segment. There should be enough bits in the buffer register 00364 * to satisfy the request; if so, no problem. 00365 */ 00366 if (nbits > bits_left) { 00367 /* Uh-oh. Report corrupted data to user and stuff zeroes into 00368 * the data stream, so that we can produce some kind of image. 00369 * We use a nonvolatile flag to ensure that only one warning message 00370 * appears per data segment. 00371 */ 00372 if (! cinfo->entropy->insufficient_data) { 00373 WARNMS(cinfo, JWRN_HIT_MARKER); 00374 cinfo->entropy->insufficient_data = TRUE; 00375 } 00376 /* Fill the buffer with zero bits */ 00377 get_buffer <<= MIN_GET_BITS - bits_left; 00378 bits_left = MIN_GET_BITS; 00379 } 00380 } 00381 00382 /* Unload the local registers */ 00383 state->next_input_byte = next_input_byte; 00384 state->bytes_in_buffer = bytes_in_buffer; 00385 state->get_buffer = get_buffer; 00386 state->bits_left = bits_left; 00387 00388 return TRUE; 00389 } |
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Definition at line 398 of file jdhuff.c. References bit_buf_type, bitread_working_state::bits_left, bits_left, CHECK_BIT_BUFFER, bitread_working_state::cinfo, GET_BITS, bitread_working_state::get_buffer, get_buffer, JHUFF_TBL::huffval, INT32, l, d_derived_tbl::maxcode, min_bits, d_derived_tbl::pub, d_derived_tbl::valoffset, and WARNMS.
00401 { 00402 register int l = min_bits; 00403 register INT32 code; 00404 00405 /* HUFF_DECODE has determined that the code is at least min_bits */ 00406 /* bits long, so fetch that many bits in one swoop. */ 00407 00408 CHECK_BIT_BUFFER(*state, l, return -1); 00409 code = GET_BITS(l); 00410 00411 /* Collect the rest of the Huffman code one bit at a time. */ 00412 /* This is per Figure F.16 in the JPEG spec. */ 00413 00414 while (code > htbl->maxcode[l]) { 00415 code <<= 1; 00416 CHECK_BIT_BUFFER(*state, 1, return -1); 00417 code |= GET_BITS(1); 00418 l++; 00419 } 00420 00421 /* Unload the local registers */ 00422 state->get_buffer = get_buffer; 00423 state->bits_left = bits_left; 00424 00425 /* With garbage input we may reach the sentinel value l = 17. */ 00426 00427 if (l > 16) { 00428 WARNMS(state->cinfo, JWRN_HUFF_BAD_CODE); 00429 return 0; /* fake a zero as the safest result */ 00430 } 00431 00432 return htbl->pub->huffval[ (int) (code + htbl->valoffset[l]) ]; 00433 } |
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Definition at line 149 of file jdhuff.c. References jpeg_decompress_struct::ac_huff_tbl_ptrs, JHUFF_TBL::bits, jpeg_decompress_struct::dc_huff_tbl_ptrs, ERREXIT, ERREXIT1, HUFF_LOOKAHEAD, JHUFF_TBL::huffval, i, JPOOL_IMAGE, L, l, d_derived_tbl::look_nbits, d_derived_tbl::look_sym, d_derived_tbl::maxcode, MEMZERO, NUM_HUFF_TBLS, p, d_derived_tbl::pub, SIZEOF, and d_derived_tbl::valoffset. Referenced by start_pass_huff_decoder(), and start_pass_phuff_decoder().
00151 { 00152 JHUFF_TBL *htbl; 00153 d_derived_tbl *dtbl; 00154 int p, i, l, si, numsymbols; 00155 int lookbits, ctr; 00156 char huffsize[257]; 00157 unsigned int huffcode[257]; 00158 unsigned int code; 00159 00160 /* Note that huffsize[] and huffcode[] are filled in code-length order, 00161 * paralleling the order of the symbols themselves in htbl->huffval[]. 00162 */ 00163 00164 /* Find the input Huffman table */ 00165 if (tblno < 0 || tblno >= NUM_HUFF_TBLS) 00166 ERREXIT1(cinfo, JERR_NO_HUFF_TABLE, tblno); 00167 htbl = 00168 isDC ? cinfo->dc_huff_tbl_ptrs[tblno] : cinfo->ac_huff_tbl_ptrs[tblno]; 00169 if (htbl == NULL) 00170 ERREXIT1(cinfo, JERR_NO_HUFF_TABLE, tblno); 00171 00172 /* Allocate a workspace if we haven't already done so. */ 00173 if (*pdtbl == NULL) 00174 *pdtbl = (d_derived_tbl *) 00175 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, 00176 SIZEOF(d_derived_tbl)); 00177 dtbl = *pdtbl; 00178 dtbl->pub = htbl; /* fill in back link */ 00179 00180 /* Figure C.1: make table of Huffman code length for each symbol */ 00181 00182 p = 0; 00183 for (l = 1; l <= 16; l++) { 00184 i = (int) htbl->bits[l]; 00185 if (i < 0 || p + i > 256) /* protect against table overrun */ 00186 ERREXIT(cinfo, JERR_BAD_HUFF_TABLE); 00187 while (i--) 00188 huffsize[p++] = (char) l; 00189 } 00190 huffsize[p] = 0; 00191 numsymbols = p; 00192 00193 /* Figure C.2: generate the codes themselves */ 00194 /* We also validate that the counts represent a legal Huffman code tree. */ 00195 00196 code = 0; 00197 si = huffsize[0]; 00198 p = 0; 00199 while (huffsize[p]) { 00200 while (((int) huffsize[p]) == si) { 00201 huffcode[p++] = code; 00202 code++; 00203 } 00204 /* code is now 1 more than the last code used for codelength si; but 00205 * it must still fit in si bits, since no code is allowed to be all ones. 00206 */ 00207 if (((INT32) code) >= (((INT32) 1) << si)) 00208 ERREXIT(cinfo, JERR_BAD_HUFF_TABLE); 00209 code <<= 1; 00210 si++; 00211 } 00212 00213 /* Figure F.15: generate decoding tables for bit-sequential decoding */ 00214 00215 p = 0; 00216 for (l = 1; l <= 16; l++) { 00217 if (htbl->bits[l]) { 00218 /* valoffset[l] = huffval[] index of 1st symbol of code length l, 00219 * minus the minimum code of length l 00220 */ 00221 dtbl->valoffset[l] = (INT32) p - (INT32) huffcode[p]; 00222 p += htbl->bits[l]; 00223 dtbl->maxcode[l] = huffcode[p-1]; /* maximum code of length l */ 00224 } else { 00225 dtbl->maxcode[l] = -1; /* -1 if no codes of this length */ 00226 } 00227 } 00228 dtbl->maxcode[17] = 0xFFFFFL; /* ensures jpeg_huff_decode terminates */ 00229 00230 /* Compute lookahead tables to speed up decoding. 00231 * First we set all the table entries to 0, indicating "too long"; 00232 * then we iterate through the Huffman codes that are short enough and 00233 * fill in all the entries that correspond to bit sequences starting 00234 * with that code. 00235 */ 00236 00237 MEMZERO(dtbl->look_nbits, SIZEOF(dtbl->look_nbits)); 00238 00239 p = 0; 00240 for (l = 1; l <= HUFF_LOOKAHEAD; l++) { 00241 for (i = 1; i <= (int) htbl->bits[l]; i++, p++) { 00242 /* l = current code's length, p = its index in huffcode[] & huffval[]. */ 00243 /* Generate left-justified code followed by all possible bit sequences */ 00244 lookbits = huffcode[p] << (HUFF_LOOKAHEAD-l); 00245 for (ctr = 1 << (HUFF_LOOKAHEAD-l); ctr > 0; ctr--) { 00246 dtbl->look_nbits[lookbits] = l; 00247 dtbl->look_sym[lookbits] = htbl->huffval[p]; 00248 lookbits++; 00249 } 00250 } 00251 } 00252 00253 /* Validate symbols as being reasonable. 00254 * For AC tables, we make no check, but accept all byte values 0..255. 00255 * For DC tables, we require the symbols to be in range 0..15. 00256 * (Tighter bounds could be applied depending on the data depth and mode, 00257 * but this is sufficient to ensure safe decoding.) 00258 */ 00259 if (isDC) { 00260 for (i = 0; i < numsymbols; i++) { 00261 int sym = htbl->huffval[i]; 00262 if (sym < 0 || sym > 15) 00263 ERREXIT(cinfo, JERR_BAD_HUFF_TABLE); 00264 } 00265 } 00266 } |
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Definition at line 468 of file jdhuff.c. References bitread_perm_state::bits_left, huff_entropy_decoder::bitstate, jpeg_decompress_struct::comps_in_scan, jpeg_marker_reader::discarded_bytes, jpeg_decompress_struct::entropy, jpeg_entropy_decoder::insufficient_data, savable_state::last_dc_val, jpeg_decompress_struct::marker, huff_entropy_decoder::pub, jpeg_marker_reader::read_restart_marker, jpeg_decompress_struct::restart_interval, huff_entropy_decoder::restarts_to_go, huff_entropy_decoder::saved, and jpeg_decompress_struct::unread_marker.
00469 { 00470 huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy; 00471 int ci; 00472 00473 /* Throw away any unused bits remaining in bit buffer; */ 00474 /* include any full bytes in next_marker's count of discarded bytes */ 00475 cinfo->marker->discarded_bytes += entropy->bitstate.bits_left / 8; 00476 entropy->bitstate.bits_left = 0; 00477 00478 /* Advance past the RSTn marker */ 00479 if (! (*cinfo->marker->read_restart_marker) (cinfo)) 00480 return FALSE; 00481 00482 /* Re-initialize DC predictions to 0 */ 00483 for (ci = 0; ci < cinfo->comps_in_scan; ci++) 00484 entropy->saved.last_dc_val[ci] = 0; 00485 00486 /* Reset restart counter */ 00487 entropy->restarts_to_go = cinfo->restart_interval; 00488 00489 /* Reset out-of-data flag, unless read_restart_marker left us smack up 00490 * against a marker. In that case we will end up treating the next data 00491 * segment as empty, and we can avoid producing bogus output pixels by 00492 * leaving the flag set. 00493 */ 00494 if (cinfo->unread_marker == 0) 00495 entropy->pub.insufficient_data = FALSE; 00496 00497 return TRUE; 00498 } |
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Definition at line 86 of file jdhuff.c. References huff_entropy_decoder::ac_cur_tbls, huff_entropy_decoder::ac_derived_tbls, huff_entropy_decoder::ac_needed, jpeg_component_info::ac_tbl_no, jpeg_decompress_struct::Ah, jpeg_decompress_struct::Al, bitread_perm_state::bits_left, huff_entropy_decoder::bitstate, jpeg_decompress_struct::blocks_in_MCU, jpeg_component_info::component_needed, compptr, jpeg_decompress_struct::comps_in_scan, jpeg_decompress_struct::cur_comp_info, huff_entropy_decoder::dc_cur_tbls, huff_entropy_decoder::dc_derived_tbls, huff_entropy_decoder::dc_needed, jpeg_component_info::dc_tbl_no, jpeg_component_info::DCT_scaled_size, jpeg_decompress_struct::entropy, bitread_perm_state::get_buffer, jpeg_entropy_decoder::insufficient_data, jpeg_make_d_derived_tbl(), savable_state::last_dc_val, jpeg_decompress_struct::MCU_membership, huff_entropy_decoder::pub, jpeg_decompress_struct::restart_interval, huff_entropy_decoder::restarts_to_go, huff_entropy_decoder::saved, jpeg_decompress_struct::Se, jpeg_decompress_struct::Ss, and WARNMS. Referenced by jinit_huff_decoder().
00087 { 00088 huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy; 00089 int ci, blkn, dctbl, actbl; 00090 jpeg_component_info * compptr; 00091 00092 /* Check that the scan parameters Ss, Se, Ah/Al are OK for sequential JPEG. 00093 * This ought to be an error condition, but we make it a warning because 00094 * there are some baseline files out there with all zeroes in these bytes. 00095 */ 00096 if (cinfo->Ss != 0 || cinfo->Se != DCTSIZE2-1 || 00097 cinfo->Ah != 0 || cinfo->Al != 0) 00098 WARNMS(cinfo, JWRN_NOT_SEQUENTIAL); 00099 00100 for (ci = 0; ci < cinfo->comps_in_scan; ci++) { 00101 compptr = cinfo->cur_comp_info[ci]; 00102 dctbl = compptr->dc_tbl_no; 00103 actbl = compptr->ac_tbl_no; 00104 /* Compute derived values for Huffman tables */ 00105 /* We may do this more than once for a table, but it's not expensive */ 00106 jpeg_make_d_derived_tbl(cinfo, TRUE, dctbl, 00107 & entropy->dc_derived_tbls[dctbl]); 00108 jpeg_make_d_derived_tbl(cinfo, FALSE, actbl, 00109 & entropy->ac_derived_tbls[actbl]); 00110 /* Initialize DC predictions to 0 */ 00111 entropy->saved.last_dc_val[ci] = 0; 00112 } 00113 00114 /* Precalculate decoding info for each block in an MCU of this scan */ 00115 for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) { 00116 ci = cinfo->MCU_membership[blkn]; 00117 compptr = cinfo->cur_comp_info[ci]; 00118 /* Precalculate which table to use for each block */ 00119 entropy->dc_cur_tbls[blkn] = entropy->dc_derived_tbls[compptr->dc_tbl_no]; 00120 entropy->ac_cur_tbls[blkn] = entropy->ac_derived_tbls[compptr->ac_tbl_no]; 00121 /* Decide whether we really care about the coefficient values */ 00122 if (compptr->component_needed) { 00123 entropy->dc_needed[blkn] = TRUE; 00124 /* we don't need the ACs if producing a 1/8th-size image */ 00125 entropy->ac_needed[blkn] = (compptr->DCT_scaled_size > 1); 00126 } else { 00127 entropy->dc_needed[blkn] = entropy->ac_needed[blkn] = FALSE; 00128 } 00129 } 00130 00131 /* Initialize bitread state variables */ 00132 entropy->bitstate.bits_left = 0; 00133 entropy->bitstate.get_buffer = 0; /* unnecessary, but keeps Purify quiet */ 00134 entropy->pub.insufficient_data = FALSE; 00135 00136 /* Initialize restart counter */ 00137 entropy->restarts_to_go = cinfo->restart_interval; 00138 } |
Variable Documentation
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Initial value: { 0, ((-1)<<1) + 1, ((-1)<<2) + 1, ((-1)<<3) + 1, ((-1)<<4) + 1, ((-1)<<5) + 1, ((-1)<<6) + 1, ((-1)<<7) + 1, ((-1)<<8) + 1, ((-1)<<9) + 1, ((-1)<<10) + 1, ((-1)<<11) + 1, ((-1)<<12) + 1, ((-1)<<13) + 1, ((-1)<<14) + 1, ((-1)<<15) + 1 } |
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Initial value: { 0, 0x0001, 0x0002, 0x0004, 0x0008, 0x0010, 0x0020, 0x0040, 0x0080, 0x0100, 0x0200, 0x0400, 0x0800, 0x1000, 0x2000, 0x4000 } |