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+/*
+ * jcarith.c
+ *
+ * This file was part of the Independent JPEG Group's software:
+ * Developed 1997-2009 by Guido Vollbeding.
+ * libjpeg-turbo Modifications:
+ * Copyright (C) 2015, 2018, 2021-2022, D. R. Commander.
+ * For conditions of distribution and use, see the accompanying README.ijg
+ * file.
+ *
+ * This file contains portable arithmetic entropy encoding routines for JPEG
+ * (implementing Recommendation ITU-T T.81 | ISO/IEC 10918-1).
+ *
+ * Both sequential and progressive modes are supported in this single module.
+ *
+ * Suspension is not currently supported in this module.
+ *
+ * NOTE: All referenced figures are from
+ * Recommendation ITU-T T.81 (1992) | ISO/IEC 10918-1:1994.
+ */
+
+#define JPEG_INTERNALS
+#include "jinclude.h"
+#include "jpeglib.h"
+
+
+/* Expanded entropy encoder object for arithmetic encoding. */
+
+typedef struct {
+ struct jpeg_entropy_encoder pub; /* public fields */
+
+ JLONG c; /* C register, base of coding interval, layout as in sec. D.1.3 */
+ JLONG a; /* A register, normalized size of coding interval */
+ JLONG sc; /* counter for stacked 0xFF values which might overflow */
+ JLONG zc; /* counter for pending 0x00 output values which might *
+ * be discarded at the end ("Pacman" termination) */
+ int ct; /* bit shift counter, determines when next byte will be written */
+ int buffer; /* buffer for most recent output byte != 0xFF */
+
+ int last_dc_val[MAX_COMPS_IN_SCAN]; /* last DC coef for each component */
+ int dc_context[MAX_COMPS_IN_SCAN]; /* context index for DC conditioning */
+
+ unsigned int restarts_to_go; /* MCUs left in this restart interval */
+ int next_restart_num; /* next restart number to write (0-7) */
+
+ /* Pointers to statistics areas (these workspaces have image lifespan) */
+ unsigned char *dc_stats[NUM_ARITH_TBLS];
+ unsigned char *ac_stats[NUM_ARITH_TBLS];
+
+ /* Statistics bin for coding with fixed probability 0.5 */
+ unsigned char fixed_bin[4];
+} arith_entropy_encoder;
+
+typedef arith_entropy_encoder *arith_entropy_ptr;
+
+/* The following two definitions specify the allocation chunk size
+ * for the statistics area.
+ * According to sections F.1.4.4.1.3 and F.1.4.4.2, we need at least
+ * 49 statistics bins for DC, and 245 statistics bins for AC coding.
+ *
+ * We use a compact representation with 1 byte per statistics bin,
+ * thus the numbers directly represent byte sizes.
+ * This 1 byte per statistics bin contains the meaning of the MPS
+ * (more probable symbol) in the highest bit (mask 0x80), and the
+ * index into the probability estimation state machine table
+ * in the lower bits (mask 0x7F).
+ */
+
+#define DC_STAT_BINS 64
+#define AC_STAT_BINS 256
+
+/* NOTE: Uncomment the following #define if you want to use the
+ * given formula for calculating the AC conditioning parameter Kx
+ * for spectral selection progressive coding in section G.1.3.2
+ * of the spec (Kx = Kmin + SRL (8 + Se - Kmin) 4).
+ * Although the spec and P&M authors claim that this "has proven
+ * to give good results for 8 bit precision samples", I'm not
+ * convinced yet that this is really beneficial.
+ * Early tests gave only very marginal compression enhancements
+ * (a few - around 5 or so - bytes even for very large files),
+ * which would turn out rather negative if we'd suppress the
+ * DAC (Define Arithmetic Conditioning) marker segments for
+ * the default parameters in the future.
+ * Note that currently the marker writing module emits 12-byte
+ * DAC segments for a full-component scan in a color image.
+ * This is not worth worrying about IMHO. However, since the
+ * spec defines the default values to be used if the tables
+ * are omitted (unlike Huffman tables, which are required
+ * anyway), one might optimize this behaviour in the future,
+ * and then it would be disadvantageous to use custom tables if
+ * they don't provide sufficient gain to exceed the DAC size.
+ *
+ * On the other hand, I'd consider it as a reasonable result
+ * that the conditioning has no significant influence on the
+ * compression performance. This means that the basic
+ * statistical model is already rather stable.
+ *
+ * Thus, at the moment, we use the default conditioning values
+ * anyway, and do not use the custom formula.
+ *
+#define CALCULATE_SPECTRAL_CONDITIONING
+ */
+
+/* IRIGHT_SHIFT is like RIGHT_SHIFT, but works on int rather than JLONG.
+ * We assume that int right shift is unsigned if JLONG right shift is,
+ * which should be safe.
+ */
+
+#ifdef RIGHT_SHIFT_IS_UNSIGNED
+#define ISHIFT_TEMPS int ishift_temp;
+#define IRIGHT_SHIFT(x, shft) \
+ ((ishift_temp = (x)) < 0 ? \
+ (ishift_temp >> (shft)) | ((~0) << (16 - (shft))) : \
+ (ishift_temp >> (shft)))
+#else
+#define ISHIFT_TEMPS
+#define IRIGHT_SHIFT(x, shft) ((x) >> (shft))
+#endif
+
+
+LOCAL(void)
+emit_byte(int val, j_compress_ptr cinfo)
+/* Write next output byte; we do not support suspension in this module. */
+{
+ struct jpeg_destination_mgr *dest = cinfo->dest;
+
+ *dest->next_output_byte++ = (JOCTET)val;
+ if (--dest->free_in_buffer == 0)
+ if (!(*dest->empty_output_buffer) (cinfo))
+ ERREXIT(cinfo, JERR_CANT_SUSPEND);
+}
+
+
+/*
+ * Finish up at the end of an arithmetic-compressed scan.
+ */
+
+METHODDEF(void)
+finish_pass(j_compress_ptr cinfo)
+{
+ arith_entropy_ptr e = (arith_entropy_ptr)cinfo->entropy;
+ JLONG temp;
+
+ /* Section D.1.8: Termination of encoding */
+
+ /* Find the e->c in the coding interval with the largest
+ * number of trailing zero bits */
+ if ((temp = (e->a - 1 + e->c) & 0xFFFF0000UL) < e->c)
+ e->c = temp + 0x8000L;
+ else
+ e->c = temp;
+ /* Send remaining bytes to output */
+ e->c <<= e->ct;
+ if (e->c & 0xF8000000UL) {
+ /* One final overflow has to be handled */
+ if (e->buffer >= 0) {
+ if (e->zc)
+ do emit_byte(0x00, cinfo);
+ while (--e->zc);
+ emit_byte(e->buffer + 1, cinfo);
+ if (e->buffer + 1 == 0xFF)
+ emit_byte(0x00, cinfo);
+ }
+ e->zc += e->sc; /* carry-over converts stacked 0xFF bytes to 0x00 */
+ e->sc = 0;
+ } else {
+ if (e->buffer == 0)
+ ++e->zc;
+ else if (e->buffer >= 0) {
+ if (e->zc)
+ do emit_byte(0x00, cinfo);
+ while (--e->zc);
+ emit_byte(e->buffer, cinfo);
+ }
+ if (e->sc) {
+ if (e->zc)
+ do emit_byte(0x00, cinfo);
+ while (--e->zc);
+ do {
+ emit_byte(0xFF, cinfo);
+ emit_byte(0x00, cinfo);
+ } while (--e->sc);
+ }
+ }
+ /* Output final bytes only if they are not 0x00 */
+ if (e->c & 0x7FFF800L) {
+ if (e->zc) /* output final pending zero bytes */
+ do emit_byte(0x00, cinfo);
+ while (--e->zc);
+ emit_byte((e->c >> 19) & 0xFF, cinfo);
+ if (((e->c >> 19) & 0xFF) == 0xFF)
+ emit_byte(0x00, cinfo);
+ if (e->c & 0x7F800L) {
+ emit_byte((e->c >> 11) & 0xFF, cinfo);
+ if (((e->c >> 11) & 0xFF) == 0xFF)
+ emit_byte(0x00, cinfo);
+ }
+ }
+}
+
+
+/*
+ * The core arithmetic encoding routine (common in JPEG and JBIG).
+ * This needs to go as fast as possible.
+ * Machine-dependent optimization facilities
+ * are not utilized in this portable implementation.
+ * However, this code should be fairly efficient and
+ * may be a good base for further optimizations anyway.
+ *
+ * Parameter 'val' to be encoded may be 0 or 1 (binary decision).
+ *
+ * Note: I've added full "Pacman" termination support to the
+ * byte output routines, which is equivalent to the optional
+ * Discard_final_zeros procedure (Figure D.15) in the spec.
+ * Thus, we always produce the shortest possible output
+ * stream compliant to the spec (no trailing zero bytes,
+ * except for FF stuffing).
+ *
+ * I've also introduced a new scheme for accessing
+ * the probability estimation state machine table,
+ * derived from Markus Kuhn's JBIG implementation.
+ */
+
+LOCAL(void)
+arith_encode(j_compress_ptr cinfo, unsigned char *st, int val)
+{
+ register arith_entropy_ptr e = (arith_entropy_ptr)cinfo->entropy;
+ register unsigned char nl, nm;
+ register JLONG qe, temp;
+ register int sv;
+
+ /* Fetch values from our compact representation of Table D.2:
+ * Qe values and probability estimation state machine
+ */
+ sv = *st;
+ qe = jpeg_aritab[sv & 0x7F]; /* => Qe_Value */
+ nl = qe & 0xFF; qe >>= 8; /* Next_Index_LPS + Switch_MPS */
+ nm = qe & 0xFF; qe >>= 8; /* Next_Index_MPS */
+
+ /* Encode & estimation procedures per sections D.1.4 & D.1.5 */
+ e->a -= qe;
+ if (val != (sv >> 7)) {
+ /* Encode the less probable symbol */
+ if (e->a >= qe) {
+ /* If the interval size (qe) for the less probable symbol (LPS)
+ * is larger than the interval size for the MPS, then exchange
+ * the two symbols for coding efficiency, otherwise code the LPS
+ * as usual: */
+ e->c += e->a;
+ e->a = qe;
+ }
+ *st = (sv & 0x80) ^ nl; /* Estimate_after_LPS */
+ } else {
+ /* Encode the more probable symbol */
+ if (e->a >= 0x8000L)
+ return; /* A >= 0x8000 -> ready, no renormalization required */
+ if (e->a < qe) {
+ /* If the interval size (qe) for the less probable symbol (LPS)
+ * is larger than the interval size for the MPS, then exchange
+ * the two symbols for coding efficiency: */
+ e->c += e->a;
+ e->a = qe;
+ }
+ *st = (sv & 0x80) ^ nm; /* Estimate_after_MPS */
+ }
+
+ /* Renormalization & data output per section D.1.6 */
+ do {
+ e->a <<= 1;
+ e->c <<= 1;
+ if (--e->ct == 0) {
+ /* Another byte is ready for output */
+ temp = e->c >> 19;
+ if (temp > 0xFF) {
+ /* Handle overflow over all stacked 0xFF bytes */
+ if (e->buffer >= 0) {
+ if (e->zc)
+ do emit_byte(0x00, cinfo);
+ while (--e->zc);
+ emit_byte(e->buffer + 1, cinfo);
+ if (e->buffer + 1 == 0xFF)
+ emit_byte(0x00, cinfo);
+ }
+ e->zc += e->sc; /* carry-over converts stacked 0xFF bytes to 0x00 */
+ e->sc = 0;
+ /* Note: The 3 spacer bits in the C register guarantee
+ * that the new buffer byte can't be 0xFF here
+ * (see page 160 in the P&M JPEG book). */
+ e->buffer = temp & 0xFF; /* new output byte, might overflow later */
+ } else if (temp == 0xFF) {
+ ++e->sc; /* stack 0xFF byte (which might overflow later) */
+ } else {
+ /* Output all stacked 0xFF bytes, they will not overflow any more */
+ if (e->buffer == 0)
+ ++e->zc;
+ else if (e->buffer >= 0) {
+ if (e->zc)
+ do emit_byte(0x00, cinfo);
+ while (--e->zc);
+ emit_byte(e->buffer, cinfo);
+ }
+ if (e->sc) {
+ if (e->zc)
+ do emit_byte(0x00, cinfo);
+ while (--e->zc);
+ do {
+ emit_byte(0xFF, cinfo);
+ emit_byte(0x00, cinfo);
+ } while (--e->sc);
+ }
+ e->buffer = temp & 0xFF; /* new output byte (can still overflow) */
+ }
+ e->c &= 0x7FFFFL;
+ e->ct += 8;
+ }
+ } while (e->a < 0x8000L);
+}
+
+
+/*
+ * Emit a restart marker & resynchronize predictions.
+ */
+
+LOCAL(void)
+emit_restart(j_compress_ptr cinfo, int restart_num)
+{
+ arith_entropy_ptr entropy = (arith_entropy_ptr)cinfo->entropy;
+ int ci;
+ jpeg_component_info *compptr;
+
+ finish_pass(cinfo);
+
+ emit_byte(0xFF, cinfo);
+ emit_byte(JPEG_RST0 + restart_num, cinfo);
+
+ /* Re-initialize statistics areas */
+ for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
+ compptr = cinfo->cur_comp_info[ci];
+ /* DC needs no table for refinement scan */
+ if (cinfo->progressive_mode == 0 || (cinfo->Ss == 0 && cinfo->Ah == 0)) {
+ memset(entropy->dc_stats[compptr->dc_tbl_no], 0, DC_STAT_BINS);
+ /* Reset DC predictions to 0 */
+ entropy->last_dc_val[ci] = 0;
+ entropy->dc_context[ci] = 0;
+ }
+ /* AC needs no table when not present */
+ if (cinfo->progressive_mode == 0 || cinfo->Se) {
+ memset(entropy->ac_stats[compptr->ac_tbl_no], 0, AC_STAT_BINS);
+ }
+ }
+
+ /* Reset arithmetic encoding variables */
+ entropy->c = 0;
+ entropy->a = 0x10000L;
+ entropy->sc = 0;
+ entropy->zc = 0;
+ entropy->ct = 11;
+ entropy->buffer = -1; /* empty */
+}
+
+
+/*
+ * MCU encoding for DC initial scan (either spectral selection,
+ * or first pass of successive approximation).
+ */
+
+METHODDEF(boolean)
+encode_mcu_DC_first(j_compress_ptr cinfo, JBLOCKROW *MCU_data)
+{
+ arith_entropy_ptr entropy = (arith_entropy_ptr)cinfo->entropy;
+ JBLOCKROW block;
+ unsigned char *st;
+ int blkn, ci, tbl;
+ int v, v2, m;
+ ISHIFT_TEMPS
+
+ /* Emit restart marker if needed */
+ if (cinfo->restart_interval) {
+ if (entropy->restarts_to_go == 0) {
+ emit_restart(cinfo, entropy->next_restart_num);
+ entropy->restarts_to_go = cinfo->restart_interval;
+ entropy->next_restart_num++;
+ entropy->next_restart_num &= 7;
+ }
+ entropy->restarts_to_go--;
+ }
+
+ /* Encode the MCU data blocks */
+ for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {
+ block = MCU_data[blkn];
+ ci = cinfo->MCU_membership[blkn];
+ tbl = cinfo->cur_comp_info[ci]->dc_tbl_no;
+
+ /* Compute the DC value after the required point transform by Al.
+ * This is simply an arithmetic right shift.
+ */
+ m = IRIGHT_SHIFT((int)((*block)[0]), cinfo->Al);
+
+ /* Sections F.1.4.1 & F.1.4.4.1: Encoding of DC coefficients */
+
+ /* Table F.4: Point to statistics bin S0 for DC coefficient coding */
+ st = entropy->dc_stats[tbl] + entropy->dc_context[ci];
+
+ /* Figure F.4: Encode_DC_DIFF */
+ if ((v = m - entropy->last_dc_val[ci]) == 0) {
+ arith_encode(cinfo, st, 0);
+ entropy->dc_context[ci] = 0; /* zero diff category */
+ } else {
+ entropy->last_dc_val[ci] = m;
+ arith_encode(cinfo, st, 1);
+ /* Figure F.6: Encoding nonzero value v */
+ /* Figure F.7: Encoding the sign of v */
+ if (v > 0) {
+ arith_encode(cinfo, st + 1, 0); /* Table F.4: SS = S0 + 1 */
+ st += 2; /* Table F.4: SP = S0 + 2 */
+ entropy->dc_context[ci] = 4; /* small positive diff category */
+ } else {
+ v = -v;
+ arith_encode(cinfo, st + 1, 1); /* Table F.4: SS = S0 + 1 */
+ st += 3; /* Table F.4: SN = S0 + 3 */
+ entropy->dc_context[ci] = 8; /* small negative diff category */
+ }
+ /* Figure F.8: Encoding the magnitude category of v */
+ m = 0;
+ if (v -= 1) {
+ arith_encode(cinfo, st, 1);
+ m = 1;
+ v2 = v;
+ st = entropy->dc_stats[tbl] + 20; /* Table F.4: X1 = 20 */
+ while (v2 >>= 1) {
+ arith_encode(cinfo, st, 1);
+ m <<= 1;
+ st += 1;
+ }
+ }
+ arith_encode(cinfo, st, 0);
+ /* 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] += 8; /* large diff category */
+ /* Figure F.9: Encoding the magnitude bit pattern of v */
+ st += 14;
+ while (m >>= 1)
+ arith_encode(cinfo, st, (m & v) ? 1 : 0);
+ }
+ }
+
+ return TRUE;
+}
+
+
+/*
+ * MCU encoding for AC initial scan (either spectral selection,
+ * or first pass of successive approximation).
+ */
+
+METHODDEF(boolean)
+encode_mcu_AC_first(j_compress_ptr cinfo, JBLOCKROW *MCU_data)
+{
+ arith_entropy_ptr entropy = (arith_entropy_ptr)cinfo->entropy;
+ JBLOCKROW block;
+ unsigned char *st;
+ int tbl, k, ke;
+ int v, v2, m;
+
+ /* Emit restart marker if needed */
+ if (cinfo->restart_interval) {
+ if (entropy->restarts_to_go == 0) {
+ emit_restart(cinfo, entropy->next_restart_num);
+ entropy->restarts_to_go = cinfo->restart_interval;
+ entropy->next_restart_num++;
+ entropy->next_restart_num &= 7;
+ }
+ entropy->restarts_to_go--;
+ }
+
+ /* Encode the MCU data block */
+ block = MCU_data[0];
+ tbl = cinfo->cur_comp_info[0]->ac_tbl_no;
+
+ /* Sections F.1.4.2 & F.1.4.4.2: Encoding of AC coefficients */
+
+ /* Establish EOB (end-of-block) index */
+ for (ke = cinfo->Se; ke > 0; ke--)
+ /* We must apply the point transform by Al. For AC coefficients this
+ * is an integer division with rounding towards 0. To do this portably
+ * in C, we shift after obtaining the absolute value.
+ */
+ if ((v = (*block)[jpeg_natural_order[ke]]) >= 0) {
+ if (v >>= cinfo->Al) break;
+ } else {
+ v = -v;
+ if (v >>= cinfo->Al) break;
+ }
+
+ /* Figure F.5: Encode_AC_Coefficients */
+ for (k = cinfo->Ss; k <= ke; k++) {
+ st = entropy->ac_stats[tbl] + 3 * (k - 1);
+ arith_encode(cinfo, st, 0); /* EOB decision */
+ for (;;) {
+ if ((v = (*block)[jpeg_natural_order[k]]) >= 0) {
+ if (v >>= cinfo->Al) {
+ arith_encode(cinfo, st + 1, 1);
+ arith_encode(cinfo, entropy->fixed_bin, 0);
+ break;
+ }
+ } else {
+ v = -v;
+ if (v >>= cinfo->Al) {
+ arith_encode(cinfo, st + 1, 1);
+ arith_encode(cinfo, entropy->fixed_bin, 1);
+ break;
+ }
+ }
+ arith_encode(cinfo, st + 1, 0); st += 3; k++;
+ }
+ st += 2;
+ /* Figure F.8: Encoding the magnitude category of v */
+ m = 0;
+ if (v -= 1) {
+ arith_encode(cinfo, st, 1);
+ m = 1;
+ v2 = v;
+ if (v2 >>= 1) {
+ arith_encode(cinfo, st, 1);
+ m <<= 1;
+ st = entropy->ac_stats[tbl] +
+ (k <= cinfo->arith_ac_K[tbl] ? 189 : 217);
+ while (v2 >>= 1) {
+ arith_encode(cinfo, st, 1);
+ m <<= 1;
+ st += 1;
+ }
+ }
+ }
+ arith_encode(cinfo, st, 0);
+ /* Figure F.9: Encoding the magnitude bit pattern of v */
+ st += 14;
+ while (m >>= 1)
+ arith_encode(cinfo, st, (m & v) ? 1 : 0);
+ }
+ /* Encode EOB decision only if k <= cinfo->Se */
+ if (k <= cinfo->Se) {
+ st = entropy->ac_stats[tbl] + 3 * (k - 1);
+ arith_encode(cinfo, st, 1);
+ }
+
+ return TRUE;
+}
+
+
+/*
+ * MCU encoding for DC successive approximation refinement scan.
+ */
+
+METHODDEF(boolean)
+encode_mcu_DC_refine(j_compress_ptr cinfo, JBLOCKROW *MCU_data)
+{
+ arith_entropy_ptr entropy = (arith_entropy_ptr)cinfo->entropy;
+ unsigned char *st;
+ int Al, blkn;
+
+ /* Emit restart marker if needed */
+ if (cinfo->restart_interval) {
+ if (entropy->restarts_to_go == 0) {
+ emit_restart(cinfo, entropy->next_restart_num);
+ entropy->restarts_to_go = cinfo->restart_interval;
+ entropy->next_restart_num++;
+ entropy->next_restart_num &= 7;
+ }
+ entropy->restarts_to_go--;
+ }
+
+ st = entropy->fixed_bin; /* use fixed probability estimation */
+ Al = cinfo->Al;
+
+ /* Encode the MCU data blocks */
+ for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {
+ /* We simply emit the Al'th bit of the DC coefficient value. */
+ arith_encode(cinfo, st, (MCU_data[blkn][0][0] >> Al) & 1);
+ }
+
+ return TRUE;
+}
+
+
+/*
+ * MCU encoding for AC successive approximation refinement scan.
+ */
+
+METHODDEF(boolean)
+encode_mcu_AC_refine(j_compress_ptr cinfo, JBLOCKROW *MCU_data)
+{
+ arith_entropy_ptr entropy = (arith_entropy_ptr)cinfo->entropy;
+ JBLOCKROW block;
+ unsigned char *st;
+ int tbl, k, ke, kex;
+ int v;
+
+ /* Emit restart marker if needed */
+ if (cinfo->restart_interval) {
+ if (entropy->restarts_to_go == 0) {
+ emit_restart(cinfo, entropy->next_restart_num);
+ entropy->restarts_to_go = cinfo->restart_interval;
+ entropy->next_restart_num++;
+ entropy->next_restart_num &= 7;
+ }
+ entropy->restarts_to_go--;
+ }
+
+ /* Encode the MCU data block */
+ block = MCU_data[0];
+ tbl = cinfo->cur_comp_info[0]->ac_tbl_no;
+
+ /* Section G.1.3.3: Encoding of AC coefficients */
+
+ /* Establish EOB (end-of-block) index */
+ for (ke = cinfo->Se; ke > 0; ke--)
+ /* We must apply the point transform by Al. For AC coefficients this
+ * is an integer division with rounding towards 0. To do this portably
+ * in C, we shift after obtaining the absolute value.
+ */
+ if ((v = (*block)[jpeg_natural_order[ke]]) >= 0) {
+ if (v >>= cinfo->Al) break;
+ } else {
+ v = -v;
+ if (v >>= cinfo->Al) break;
+ }
+
+ /* Establish EOBx (previous stage end-of-block) index */
+ for (kex = ke; kex > 0; kex--)
+ if ((v = (*block)[jpeg_natural_order[kex]]) >= 0) {
+ if (v >>= cinfo->Ah) break;
+ } else {
+ v = -v;
+ if (v >>= cinfo->Ah) break;
+ }
+
+ /* Figure G.10: Encode_AC_Coefficients_SA */
+ for (k = cinfo->Ss; k <= ke; k++) {
+ st = entropy->ac_stats[tbl] + 3 * (k - 1);
+ if (k > kex)
+ arith_encode(cinfo, st, 0); /* EOB decision */
+ for (;;) {
+ if ((v = (*block)[jpeg_natural_order[k]]) >= 0) {
+ if (v >>= cinfo->Al) {
+ if (v >> 1) /* previously nonzero coef */
+ arith_encode(cinfo, st + 2, (v & 1));
+ else { /* newly nonzero coef */
+ arith_encode(cinfo, st + 1, 1);
+ arith_encode(cinfo, entropy->fixed_bin, 0);
+ }
+ break;
+ }
+ } else {
+ v = -v;
+ if (v >>= cinfo->Al) {
+ if (v >> 1) /* previously nonzero coef */
+ arith_encode(cinfo, st + 2, (v & 1));
+ else { /* newly nonzero coef */
+ arith_encode(cinfo, st + 1, 1);
+ arith_encode(cinfo, entropy->fixed_bin, 1);
+ }
+ break;
+ }
+ }
+ arith_encode(cinfo, st + 1, 0); st += 3; k++;
+ }
+ }
+ /* Encode EOB decision only if k <= cinfo->Se */
+ if (k <= cinfo->Se) {
+ st = entropy->ac_stats[tbl] + 3 * (k - 1);
+ arith_encode(cinfo, st, 1);
+ }
+
+ return TRUE;
+}
+
+
+/*
+ * Encode and output one MCU's worth of arithmetic-compressed coefficients.
+ */
+
+METHODDEF(boolean)
+encode_mcu(j_compress_ptr cinfo, JBLOCKROW *MCU_data)
+{
+ arith_entropy_ptr entropy = (arith_entropy_ptr)cinfo->entropy;
+ jpeg_component_info *compptr;
+ JBLOCKROW block;
+ unsigned char *st;
+ int blkn, ci, tbl, k, ke;
+ int v, v2, m;
+
+ /* Emit restart marker if needed */
+ if (cinfo->restart_interval) {
+ if (entropy->restarts_to_go == 0) {
+ emit_restart(cinfo, entropy->next_restart_num);
+ entropy->restarts_to_go = cinfo->restart_interval;
+ entropy->next_restart_num++;
+ entropy->next_restart_num &= 7;
+ }
+ entropy->restarts_to_go--;
+ }
+
+ /* Encode the MCU data blocks */
+ for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {
+ block = MCU_data[blkn];
+ ci = cinfo->MCU_membership[blkn];
+ compptr = cinfo->cur_comp_info[ci];
+
+ /* Sections F.1.4.1 & F.1.4.4.1: Encoding of DC coefficients */
+
+ tbl = compptr->dc_tbl_no;
+
+ /* Table F.4: Point to statistics bin S0 for DC coefficient coding */
+ st = entropy->dc_stats[tbl] + entropy->dc_context[ci];
+
+ /* Figure F.4: Encode_DC_DIFF */
+ if ((v = (*block)[0] - entropy->last_dc_val[ci]) == 0) {
+ arith_encode(cinfo, st, 0);
+ entropy->dc_context[ci] = 0; /* zero diff category */
+ } else {
+ entropy->last_dc_val[ci] = (*block)[0];
+ arith_encode(cinfo, st, 1);
+ /* Figure F.6: Encoding nonzero value v */
+ /* Figure F.7: Encoding the sign of v */
+ if (v > 0) {
+ arith_encode(cinfo, st + 1, 0); /* Table F.4: SS = S0 + 1 */
+ st += 2; /* Table F.4: SP = S0 + 2 */
+ entropy->dc_context[ci] = 4; /* small positive diff category */
+ } else {
+ v = -v;
+ arith_encode(cinfo, st + 1, 1); /* Table F.4: SS = S0 + 1 */
+ st += 3; /* Table F.4: SN = S0 + 3 */
+ entropy->dc_context[ci] = 8; /* small negative diff category */
+ }
+ /* Figure F.8: Encoding the magnitude category of v */
+ m = 0;
+ if (v -= 1) {
+ arith_encode(cinfo, st, 1);
+ m = 1;
+ v2 = v;
+ st = entropy->dc_stats[tbl] + 20; /* Table F.4: X1 = 20 */
+ while (v2 >>= 1) {
+ arith_encode(cinfo, st, 1);
+ m <<= 1;
+ st += 1;
+ }
+ }
+ arith_encode(cinfo, st, 0);
+ /* 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] += 8; /* large diff category */
+ /* Figure F.9: Encoding the magnitude bit pattern of v */
+ st += 14;
+ while (m >>= 1)
+ arith_encode(cinfo, st, (m & v) ? 1 : 0);
+ }
+
+ /* Sections F.1.4.2 & F.1.4.4.2: Encoding of AC coefficients */
+
+ tbl = compptr->ac_tbl_no;
+
+ /* Establish EOB (end-of-block) index */
+ for (ke = DCTSIZE2 - 1; ke > 0; ke--)
+ if ((*block)[jpeg_natural_order[ke]]) break;
+
+ /* Figure F.5: Encode_AC_Coefficients */
+ for (k = 1; k <= ke; k++) {
+ st = entropy->ac_stats[tbl] + 3 * (k - 1);
+ arith_encode(cinfo, st, 0); /* EOB decision */
+ while ((v = (*block)[jpeg_natural_order[k]]) == 0) {
+ arith_encode(cinfo, st + 1, 0); st += 3; k++;
+ }
+ arith_encode(cinfo, st + 1, 1);
+ /* Figure F.6: Encoding nonzero value v */
+ /* Figure F.7: Encoding the sign of v */
+ if (v > 0) {
+ arith_encode(cinfo, entropy->fixed_bin, 0);
+ } else {
+ v = -v;
+ arith_encode(cinfo, entropy->fixed_bin, 1);
+ }
+ st += 2;
+ /* Figure F.8: Encoding the magnitude category of v */
+ m = 0;
+ if (v -= 1) {
+ arith_encode(cinfo, st, 1);
+ m = 1;
+ v2 = v;
+ if (v2 >>= 1) {
+ arith_encode(cinfo, st, 1);
+ m <<= 1;
+ st = entropy->ac_stats[tbl] +
+ (k <= cinfo->arith_ac_K[tbl] ? 189 : 217);
+ while (v2 >>= 1) {
+ arith_encode(cinfo, st, 1);
+ m <<= 1;
+ st += 1;
+ }
+ }
+ }
+ arith_encode(cinfo, st, 0);
+ /* Figure F.9: Encoding the magnitude bit pattern of v */
+ st += 14;
+ while (m >>= 1)
+ arith_encode(cinfo, st, (m & v) ? 1 : 0);
+ }
+ /* Encode EOB decision only if k <= DCTSIZE2 - 1 */
+ if (k <= DCTSIZE2 - 1) {
+ st = entropy->ac_stats[tbl] + 3 * (k - 1);
+ arith_encode(cinfo, st, 1);
+ }
+ }
+
+ return TRUE;
+}
+
+
+/*
+ * Initialize for an arithmetic-compressed scan.
+ */
+
+METHODDEF(void)
+start_pass(j_compress_ptr cinfo, boolean gather_statistics)
+{
+ arith_entropy_ptr entropy = (arith_entropy_ptr)cinfo->entropy;
+ int ci, tbl;
+ jpeg_component_info *compptr;
+
+ if (gather_statistics)
+ /* Make sure to avoid that in the master control logic!
+ * We are fully adaptive here and need no extra
+ * statistics gathering pass!
+ */
+ ERREXIT(cinfo, JERR_NOTIMPL);
+
+ /* We assume jcmaster.c already validated the progressive scan parameters. */
+
+ /* Select execution routines */
+ if (cinfo->progressive_mode) {
+ if (cinfo->Ah == 0) {
+ if (cinfo->Ss == 0)
+ entropy->pub.encode_mcu = encode_mcu_DC_first;
+ else
+ entropy->pub.encode_mcu = encode_mcu_AC_first;
+ } else {
+ if (cinfo->Ss == 0)
+ entropy->pub.encode_mcu = encode_mcu_DC_refine;
+ else
+ entropy->pub.encode_mcu = encode_mcu_AC_refine;
+ }
+ } else
+ entropy->pub.encode_mcu = encode_mcu;
+
+ /* Allocate & initialize requested statistics areas */
+ for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
+ compptr = cinfo->cur_comp_info[ci];
+ /* DC needs no table for refinement scan */
+ if (cinfo->progressive_mode == 0 || (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);
+ memset(entropy->dc_stats[tbl], 0, DC_STAT_BINS);
+ /* Initialize DC predictions to 0 */
+ entropy->last_dc_val[ci] = 0;
+ entropy->dc_context[ci] = 0;
+ }
+ /* AC needs no table when not present */
+ if (cinfo->progressive_mode == 0 || cinfo->Se) {
+ 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);
+ memset(entropy->ac_stats[tbl], 0, AC_STAT_BINS);
+#ifdef CALCULATE_SPECTRAL_CONDITIONING
+ if (cinfo->progressive_mode)
+ /* Section G.1.3.2: Set appropriate arithmetic conditioning value Kx */
+ cinfo->arith_ac_K[tbl] = cinfo->Ss +
+ ((8 + cinfo->Se - cinfo->Ss) >> 4);
+#endif
+ }
+ }
+
+ /* Initialize arithmetic encoding variables */
+ entropy->c = 0;
+ entropy->a = 0x10000L;
+ entropy->sc = 0;
+ entropy->zc = 0;
+ entropy->ct = 11;
+ entropy->buffer = -1; /* empty */
+
+ /* Initialize restart stuff */
+ entropy->restarts_to_go = cinfo->restart_interval;
+ entropy->next_restart_num = 0;
+}
+
+
+/*
+ * Module initialization routine for arithmetic entropy encoding.
+ */
+
+GLOBAL(void)
+jinit_arith_encoder(j_compress_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_encoder));
+ cinfo->entropy = (struct jpeg_entropy_encoder *)entropy;
+ entropy->pub.start_pass = start_pass;
+ entropy->pub.finish_pass = finish_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;
+}
generated by cgit v1.2.3 (git 2.39.1) at 2024-12-22 08:12:46 +0000