blob: ae4154532edf0fea04f34719a910b8915fdbac04 [file] [log] [blame]
/*
* jclhuff.c
*
* This file was part of the Independent JPEG Group's software:
* Copyright (C) 1991-1997, Thomas G. Lane.
* Lossless JPEG Modifications:
* Copyright (C) 1999, Ken Murchison.
* libjpeg-turbo Modifications:
* Copyright (C) 2022, D. R. Commander.
* For conditions of distribution and use, see the accompanying README.ijg
* file.
*
* This file contains Huffman entropy encoding routines for lossless JPEG.
*
* Much of the complexity here has to do with supporting output suspension.
* If the data destination module demands suspension, we want to be able to
* back up to the start of the current MCU. To do this, we copy state
* variables into local working storage, and update them back to the
* permanent JPEG objects only upon successful completion of an MCU.
*/
#define JPEG_INTERNALS
#include "jinclude.h"
#include "jpeglib.h"
#include "jlossls.h" /* Private declarations for lossless codec */
#include "jchuff.h" /* Declarations shared with jc*huff.c */
#ifdef C_LOSSLESS_SUPPORTED
/* The legal range of a spatial difference is
* -32767 .. +32768.
* Hence the magnitude should always fit in 16 bits.
*/
#define MAX_DIFF_BITS 16
/* Expanded entropy encoder object for Huffman encoding in lossless mode.
*
* The savable_state subrecord contains fields that change within an MCU,
* but must not be updated permanently until we complete the MCU.
*/
typedef struct {
size_t put_buffer; /* current bit-accumulation buffer */
int put_bits; /* # of bits now in it */
} savable_state;
typedef struct {
int ci, yoffset, MCU_width;
} lhe_input_ptr_info;
typedef struct {
struct jpeg_entropy_encoder pub; /* public fields */
savable_state saved; /* Bit buffer at start of MCU */
/* These fields are NOT loaded into local working state. */
unsigned int restarts_to_go; /* MCUs left in this restart interval */
int next_restart_num; /* next restart number to write (0-7) */
/* Pointers to derived tables (these workspaces have image lifespan) */
c_derived_tbl *derived_tbls[NUM_HUFF_TBLS];
/* Pointers to derived tables to be used for each data unit within an MCU */
c_derived_tbl *cur_tbls[C_MAX_BLOCKS_IN_MCU];
#ifdef ENTROPY_OPT_SUPPORTED /* Statistics tables for optimization */
long *count_ptrs[NUM_HUFF_TBLS];
/* Pointers to stats tables to be used for each data unit within an MCU */
long *cur_counts[C_MAX_BLOCKS_IN_MCU];
#endif
/* Pointers to the proper input difference row for each group of data units
* within an MCU. For each component, there are Vi groups of Hi data units.
*/
JDIFFROW input_ptr[C_MAX_BLOCKS_IN_MCU];
/* Number of input pointers in use for the current MCU. This is the sum
* of all Vi in the MCU.
*/
int num_input_ptrs;
/* Information used for positioning the input pointers within the input
* difference rows.
*/
lhe_input_ptr_info input_ptr_info[C_MAX_BLOCKS_IN_MCU];
/* Index of the proper input pointer for each data unit within an MCU */
int input_ptr_index[C_MAX_BLOCKS_IN_MCU];
} lhuff_entropy_encoder;
typedef lhuff_entropy_encoder *lhuff_entropy_ptr;
/* Working state while writing an MCU.
* This struct contains all the fields that are needed by subroutines.
*/
typedef struct {
JOCTET *next_output_byte; /* => next byte to write in buffer */
size_t free_in_buffer; /* # of byte spaces remaining in buffer */
savable_state cur; /* Current bit buffer & DC state */
j_compress_ptr cinfo; /* dump_buffer needs access to this */
} working_state;
/* Forward declarations */
METHODDEF(JDIMENSION) encode_mcus_huff(j_compress_ptr cinfo,
JDIFFIMAGE diff_buf,
JDIMENSION MCU_row_num,
JDIMENSION MCU_col_num,
JDIMENSION nMCU);
METHODDEF(void) finish_pass_huff(j_compress_ptr cinfo);
#ifdef ENTROPY_OPT_SUPPORTED
METHODDEF(JDIMENSION) encode_mcus_gather(j_compress_ptr cinfo,
JDIFFIMAGE diff_buf,
JDIMENSION MCU_row_num,
JDIMENSION MCU_col_num,
JDIMENSION nMCU);
METHODDEF(void) finish_pass_gather(j_compress_ptr cinfo);
#endif
/*
* Initialize for a Huffman-compressed scan.
* If gather_statistics is TRUE, we do not output anything during the scan,
* just count the Huffman symbols used and generate Huffman code tables.
*/
METHODDEF(void)
start_pass_lhuff(j_compress_ptr cinfo, boolean gather_statistics)
{
lhuff_entropy_ptr entropy = (lhuff_entropy_ptr)cinfo->entropy;
int ci, dctbl, sampn, ptrn, yoffset, xoffset;
jpeg_component_info *compptr;
if (gather_statistics) {
#ifdef ENTROPY_OPT_SUPPORTED
entropy->pub.encode_mcus = encode_mcus_gather;
entropy->pub.finish_pass = finish_pass_gather;
#else
ERREXIT(cinfo, JERR_NOT_COMPILED);
#endif
} else {
entropy->pub.encode_mcus = encode_mcus_huff;
entropy->pub.finish_pass = finish_pass_huff;
}
for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
compptr = cinfo->cur_comp_info[ci];
dctbl = compptr->dc_tbl_no;
if (gather_statistics) {
#ifdef ENTROPY_OPT_SUPPORTED
/* Check for invalid table indexes */
/* (make_c_derived_tbl does this in the other path) */
if (dctbl < 0 || dctbl >= NUM_HUFF_TBLS)
ERREXIT1(cinfo, JERR_NO_HUFF_TABLE, dctbl);
/* Allocate and zero the statistics tables */
/* Note that jpeg_gen_optimal_table expects 257 entries in each table! */
if (entropy->count_ptrs[dctbl] == NULL)
entropy->count_ptrs[dctbl] = (long *)
(*cinfo->mem->alloc_small) ((j_common_ptr)cinfo, JPOOL_IMAGE,
257 * sizeof(long));
memset(entropy->count_ptrs[dctbl], 0, 257 * sizeof(long));
#endif
} else {
/* Compute derived values for Huffman tables */
/* We may do this more than once for a table, but it's not expensive */
jpeg_make_c_derived_tbl(cinfo, TRUE, dctbl,
&entropy->derived_tbls[dctbl]);
}
}
/* Precalculate encoding info for each sample in an MCU of this scan */
for (sampn = 0, ptrn = 0; sampn < cinfo->blocks_in_MCU;) {
compptr = cinfo->cur_comp_info[cinfo->MCU_membership[sampn]];
ci = compptr->component_index;
for (yoffset = 0; yoffset < compptr->MCU_height; yoffset++, ptrn++) {
/* Precalculate the setup info for each input pointer */
entropy->input_ptr_info[ptrn].ci = ci;
entropy->input_ptr_info[ptrn].yoffset = yoffset;
entropy->input_ptr_info[ptrn].MCU_width = compptr->MCU_width;
for (xoffset = 0; xoffset < compptr->MCU_width; xoffset++, sampn++) {
/* Precalculate the input pointer index for each sample */
entropy->input_ptr_index[sampn] = ptrn;
/* Precalculate which tables to use for each sample */
entropy->cur_tbls[sampn] = entropy->derived_tbls[compptr->dc_tbl_no];
entropy->cur_counts[sampn] = entropy->count_ptrs[compptr->dc_tbl_no];
}
}
}
entropy->num_input_ptrs = ptrn;
/* Initialize bit buffer to empty */
entropy->saved.put_buffer = 0;
entropy->saved.put_bits = 0;
/* Initialize restart stuff */
entropy->restarts_to_go = cinfo->restart_interval;
entropy->next_restart_num = 0;
}
/* Outputting bytes to the file */
/* Emit a byte, taking 'action' if must suspend. */
#define emit_byte(state, val, action) { \
*(state)->next_output_byte++ = (JOCTET)(val); \
if (--(state)->free_in_buffer == 0) \
if (!dump_buffer(state)) \
{ action; } \
}
LOCAL(boolean)
dump_buffer(working_state *state)
/* Empty the output buffer; return TRUE if successful, FALSE if must suspend */
{
struct jpeg_destination_mgr *dest = state->cinfo->dest;
if (!(*dest->empty_output_buffer) (state->cinfo))
return FALSE;
/* After a successful buffer dump, must reset buffer pointers */
state->next_output_byte = dest->next_output_byte;
state->free_in_buffer = dest->free_in_buffer;
return TRUE;
}
/* Outputting bits to the file */
/* Only the right 24 bits of put_buffer are used; the valid bits are
* left-justified in this part. At most 16 bits can be passed to emit_bits
* in one call, and we never retain more than 7 bits in put_buffer
* between calls, so 24 bits are sufficient.
*/
INLINE
LOCAL(boolean)
emit_bits(working_state *state, unsigned int code, int size)
/* Emit some bits; return TRUE if successful, FALSE if must suspend */
{
/* This routine is heavily used, so it's worth coding tightly. */
register size_t put_buffer = (size_t)code;
register int put_bits = state->cur.put_bits;
/* if size is 0, caller used an invalid Huffman table entry */
if (size == 0)
ERREXIT(state->cinfo, JERR_HUFF_MISSING_CODE);
put_buffer &= (((size_t)1) << size) - 1; /* mask off any extra bits in code */
put_bits += size; /* new number of bits in buffer */
put_buffer <<= 24 - put_bits; /* align incoming bits */
put_buffer |= state->cur.put_buffer; /* and merge with old buffer contents */
while (put_bits >= 8) {
int c = (int)((put_buffer >> 16) & 0xFF);
emit_byte(state, c, return FALSE);
if (c == 0xFF) { /* need to stuff a zero byte? */
emit_byte(state, 0, return FALSE);
}
put_buffer <<= 8;
put_bits -= 8;
}
state->cur.put_buffer = put_buffer; /* update state variables */
state->cur.put_bits = put_bits;
return TRUE;
}
LOCAL(boolean)
flush_bits(working_state *state)
{
if (!emit_bits(state, 0x7F, 7)) /* fill any partial byte with ones */
return FALSE;
state->cur.put_buffer = 0; /* and reset bit-buffer to empty */
state->cur.put_bits = 0;
return TRUE;
}
/*
* Emit a restart marker & resynchronize predictions.
*/
LOCAL(boolean)
emit_restart(working_state *state, int restart_num)
{
if (!flush_bits(state))
return FALSE;
emit_byte(state, 0xFF, return FALSE);
emit_byte(state, JPEG_RST0 + restart_num, return FALSE);
/* The restart counter is not updated until we successfully write the MCU. */
return TRUE;
}
/*
* Encode and output nMCU MCUs' worth of Huffman-compressed differences.
*/
METHODDEF(JDIMENSION)
encode_mcus_huff(j_compress_ptr cinfo, JDIFFIMAGE diff_buf,
JDIMENSION MCU_row_num, JDIMENSION MCU_col_num,
JDIMENSION nMCU)
{
lhuff_entropy_ptr entropy = (lhuff_entropy_ptr)cinfo->entropy;
working_state state;
int sampn, ci, yoffset, MCU_width, ptrn;
JDIMENSION mcu_num;
/* Load up working state */
state.next_output_byte = cinfo->dest->next_output_byte;
state.free_in_buffer = cinfo->dest->free_in_buffer;
state.cur = entropy->saved;
state.cinfo = cinfo;
/* Emit restart marker if needed */
if (cinfo->restart_interval) {
if (entropy->restarts_to_go == 0)
if (!emit_restart(&state, entropy->next_restart_num))
return 0;
}
/* Set input pointer locations based on MCU_col_num */
for (ptrn = 0; ptrn < entropy->num_input_ptrs; ptrn++) {
ci = entropy->input_ptr_info[ptrn].ci;
yoffset = entropy->input_ptr_info[ptrn].yoffset;
MCU_width = entropy->input_ptr_info[ptrn].MCU_width;
entropy->input_ptr[ptrn] =
diff_buf[ci][MCU_row_num + yoffset] + (MCU_col_num * MCU_width);
}
for (mcu_num = 0; mcu_num < nMCU; mcu_num++) {
/* Inner loop handles the samples in the MCU */
for (sampn = 0; sampn < cinfo->blocks_in_MCU; sampn++) {
register int temp, temp2;
register int nbits;
c_derived_tbl *dctbl = entropy->cur_tbls[sampn];
/* Encode the difference per section H.1.2.2 */
/* Input the sample difference */
temp = *entropy->input_ptr[entropy->input_ptr_index[sampn]]++;
if (temp & 0x8000) { /* instead of temp < 0 */
temp = (-temp) & 0x7FFF; /* absolute value, mod 2^16 */
if (temp == 0) /* special case: magnitude = 32768 */
temp2 = temp = 0x8000;
temp2 = ~temp; /* one's complement of magnitude */
} else {
temp &= 0x7FFF; /* abs value mod 2^16 */
temp2 = temp; /* magnitude */
}
/* Find the number of bits needed for the magnitude of the difference */
nbits = 0;
while (temp) {
nbits++;
temp >>= 1;
}
/* Check for out-of-range difference values.
*/
if (nbits > MAX_DIFF_BITS)
ERREXIT(cinfo, JERR_BAD_DCT_COEF);
/* Emit the Huffman-coded symbol for the number of bits */
if (!emit_bits(&state, dctbl->ehufco[nbits], dctbl->ehufsi[nbits]))
return mcu_num;
/* Emit that number of bits of the value, if positive, */
/* or the complement of its magnitude, if negative. */
if (nbits && /* emit_bits rejects calls with size 0 */
nbits != 16) /* special case: no bits should be emitted */
if (!emit_bits(&state, (unsigned int)temp2, nbits))
return mcu_num;
}
/* Completed MCU, so update state */
cinfo->dest->next_output_byte = state.next_output_byte;
cinfo->dest->free_in_buffer = state.free_in_buffer;
entropy->saved = state.cur;
/* Update restart-interval state too */
if (cinfo->restart_interval) {
if (entropy->restarts_to_go == 0) {
entropy->restarts_to_go = cinfo->restart_interval;
entropy->next_restart_num++;
entropy->next_restart_num &= 7;
}
entropy->restarts_to_go--;
}
}
return nMCU;
}
/*
* Finish up at the end of a Huffman-compressed scan.
*/
METHODDEF(void)
finish_pass_huff(j_compress_ptr cinfo)
{
lhuff_entropy_ptr entropy = (lhuff_entropy_ptr)cinfo->entropy;
working_state state;
/* Load up working state ... flush_bits needs it */
state.next_output_byte = cinfo->dest->next_output_byte;
state.free_in_buffer = cinfo->dest->free_in_buffer;
state.cur = entropy->saved;
state.cinfo = cinfo;
/* Flush out the last data */
if (!flush_bits(&state))
ERREXIT(cinfo, JERR_CANT_SUSPEND);
/* Update state */
cinfo->dest->next_output_byte = state.next_output_byte;
cinfo->dest->free_in_buffer = state.free_in_buffer;
entropy->saved = state.cur;
}
/*
* Huffman coding optimization.
*
* We first scan the supplied data and count the number of uses of each symbol
* that is to be Huffman-coded. (This process MUST agree with the code above.)
* Then we build a Huffman coding tree for the observed counts.
* Symbols which are not needed at all for the particular image are not
* assigned any code, which saves space in the DHT marker as well as in
* the compressed data.
*/
#ifdef ENTROPY_OPT_SUPPORTED
/*
* Trial-encode nMCU MCUs' worth of Huffman-compressed differences.
* No data is actually output, so no suspension return is possible.
*/
METHODDEF(JDIMENSION)
encode_mcus_gather(j_compress_ptr cinfo, JDIFFIMAGE diff_buf,
JDIMENSION MCU_row_num, JDIMENSION MCU_col_num,
JDIMENSION nMCU)
{
lhuff_entropy_ptr entropy = (lhuff_entropy_ptr)cinfo->entropy;
int sampn, ci, yoffset, MCU_width, ptrn;
JDIMENSION mcu_num;
/* Take care of restart intervals if needed */
if (cinfo->restart_interval) {
if (entropy->restarts_to_go == 0) {
/* Update restart state */
entropy->restarts_to_go = cinfo->restart_interval;
}
entropy->restarts_to_go--;
}
/* Set input pointer locations based on MCU_col_num */
for (ptrn = 0; ptrn < entropy->num_input_ptrs; ptrn++) {
ci = entropy->input_ptr_info[ptrn].ci;
yoffset = entropy->input_ptr_info[ptrn].yoffset;
MCU_width = entropy->input_ptr_info[ptrn].MCU_width;
entropy->input_ptr[ptrn] =
diff_buf[ci][MCU_row_num + yoffset] + (MCU_col_num * MCU_width);
}
for (mcu_num = 0; mcu_num < nMCU; mcu_num++) {
/* Inner loop handles the samples in the MCU */
for (sampn = 0; sampn < cinfo->blocks_in_MCU; sampn++) {
register int temp;
register int nbits;
long *counts = entropy->cur_counts[sampn];
/* Encode the difference per section H.1.2.2 */
/* Input the sample difference */
temp = *entropy->input_ptr[entropy->input_ptr_index[sampn]]++;
if (temp & 0x8000) { /* instead of temp < 0 */
temp = (-temp) & 0x7FFF; /* absolute value, mod 2^16 */
if (temp == 0) /* special case: magnitude = 32768 */
temp = 0x8000;
} else
temp &= 0x7FFF; /* abs value mod 2^16 */
/* Find the number of bits needed for the magnitude of the difference */
nbits = 0;
while (temp) {
nbits++;
temp >>= 1;
}
/* Check for out-of-range difference values.
*/
if (nbits > MAX_DIFF_BITS)
ERREXIT(cinfo, JERR_BAD_DCT_COEF);
/* Count the Huffman symbol for the number of bits */
counts[nbits]++;
}
}
return nMCU;
}
/*
* Finish up a statistics-gathering pass and create the new Huffman tables.
*/
METHODDEF(void)
finish_pass_gather(j_compress_ptr cinfo)
{
lhuff_entropy_ptr entropy = (lhuff_entropy_ptr)cinfo->entropy;
int ci, dctbl;
jpeg_component_info *compptr;
JHUFF_TBL **htblptr;
boolean did_dc[NUM_HUFF_TBLS];
/* It's important not to apply jpeg_gen_optimal_table more than once
* per table, because it clobbers the input frequency counts!
*/
memset(did_dc, 0, sizeof(did_dc));
for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
compptr = cinfo->cur_comp_info[ci];
dctbl = compptr->dc_tbl_no;
if (!did_dc[dctbl]) {
htblptr = &cinfo->dc_huff_tbl_ptrs[dctbl];
if (*htblptr == NULL)
*htblptr = jpeg_alloc_huff_table((j_common_ptr)cinfo);
jpeg_gen_optimal_table(cinfo, *htblptr, entropy->count_ptrs[dctbl]);
did_dc[dctbl] = TRUE;
}
}
}
#endif /* ENTROPY_OPT_SUPPORTED */
/*
* Module initialization routine for Huffman entropy encoding.
*/
GLOBAL(void)
jinit_lhuff_encoder(j_compress_ptr cinfo)
{
lhuff_entropy_ptr entropy;
int i;
entropy = (lhuff_entropy_ptr)
(*cinfo->mem->alloc_small) ((j_common_ptr)cinfo, JPOOL_IMAGE,
sizeof(lhuff_entropy_encoder));
cinfo->entropy = (struct jpeg_entropy_encoder *)entropy;
entropy->pub.start_pass = start_pass_lhuff;
/* Mark tables unallocated */
for (i = 0; i < NUM_HUFF_TBLS; i++) {
entropy->derived_tbls[i] = NULL;
#ifdef ENTROPY_OPT_SUPPORTED
entropy->count_ptrs[i] = NULL;
#endif
}
}
#endif /* C_LOSSLESS_SUPPORTED */