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165 lines
5.3 KiB
C++
165 lines
5.3 KiB
C++
/**
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* Copyright (c) 2012-2016 Moodstocks SAS
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*
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* Permission is hereby granted, free of charge, to any person obtaining
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* a copy of this software and associated documentation files (the
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* "Software"), to deal in the Software without restriction, including
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* without limitation the rights to use, copy, modify, merge, publish,
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* distribute, sublicense, and/or sell copies of the Software, and to
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* permit persons to whom the Software is furnished to do so, subject to
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* the following conditions:
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*
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* The above copyright notice and this permission notice shall be
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* included in all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
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* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
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* LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
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* OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
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* WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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*/
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#include "huff.h"
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#include "conf.h"
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#ifdef WORD_BIT
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#define JPEC_INT_WIDTH WORD_BIT
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#else
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#define JPEC_INT_WIDTH (int)(sizeof(int) * CHAR_BIT)
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#endif
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#if __GNUC__
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#define JPEC_HUFF_NBITS(JPEC_nbits, JPEC_val) \
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JPEC_nbits = (!JPEC_val) ? 0 : JPEC_INT_WIDTH - __builtin_clz(JPEC_val)
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#else
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#define JPEC_HUFF_NBITS(JPEC_nbits, JPEC_val) \
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JPEC_nbits = 0; \
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while (val) { \
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JPEC_nbits++; \
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val >>= 1; \
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}
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#endif
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/* Private function prototypes */
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static void jpec_huff_encode_block_impl(jpec_block_t *block, jpec_huff_state_t *s);
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static void jpec_huff_write_bits(jpec_huff_state_t *s, unsigned int bits, int n);
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void jpec_huff_skel_init(jpec_huff_skel_t *skel) {
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assert(skel);
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memset(skel, 0, sizeof(*skel));
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skel->opq = jpec_huff_new();
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skel->del = (void (*)(void *))jpec_huff_del;
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skel->encode_block = (void (*)(void *, jpec_block_t *, jpec_buffer_t *))jpec_huff_encode_block;
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}
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jpec_huff_t *jpec_huff_new(void) {
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jpec_huff_t *h = (jpec_huff_t *)malloc(sizeof(*h));
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h->state.buffer = 0;
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h->state.nbits = 0;
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h->state.dc = 0;
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h->state.buf = NULL;
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return h;
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}
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void jpec_huff_del(jpec_huff_t *h) {
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assert(h);
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/* Flush any remaining bits and fill in the incomple byte (if any) with 1-s */
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jpec_huff_write_bits(&h->state, 0x7F, 7);
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free(h);
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}
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void jpec_huff_encode_block(jpec_huff_t *h, jpec_block_t *block, jpec_buffer_t *buf) {
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assert(h && block && buf);
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jpec_huff_state_t state;
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state.buffer = h->state.buffer;
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state.nbits = h->state.nbits;
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state.dc = h->state.dc;
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state.buf = buf;
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jpec_huff_encode_block_impl(block, &state);
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h->state.buffer = state.buffer;
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h->state.nbits = state.nbits;
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h->state.dc = state.dc;
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h->state.buf = state.buf;
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}
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static void jpec_huff_encode_block_impl(jpec_block_t *block, jpec_huff_state_t *s) {
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assert(block && s);
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int val, bits, nbits;
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/* DC coefficient encoding */
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if (block->len > 0) {
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val = block->zz[0] - s->dc;
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s->dc = block->zz[0];
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}
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else {
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val = -s->dc;
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s->dc = 0;
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}
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bits = val;
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if (val < 0) {
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val = -val;
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bits = ~val;
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}
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JPEC_HUFF_NBITS(nbits, val);
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jpec_huff_write_bits(s, jpec_dc_code[nbits], jpec_dc_len[nbits]);
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if (nbits) jpec_huff_write_bits(s, (unsigned int) bits, nbits);
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/* AC coefficients encoding (w/ RLE of zeros) */
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int nz = 0;
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for (int i = 1; i < block->len; i++) {
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if ((val = block->zz[i]) == 0) nz++;
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else {
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while (nz >= 16) {
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jpec_huff_write_bits(s, jpec_ac_code[0xF0], jpec_ac_len[0xF0]); /* ZRL code */
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nz -= 16;
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}
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bits = val;
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if (val < 0) {
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val = -val;
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bits = ~val;
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}
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JPEC_HUFF_NBITS(nbits, val);
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int j = (nz << 4) + nbits;
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jpec_huff_write_bits(s, jpec_ac_code[j], jpec_ac_len[j]);
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if (nbits) jpec_huff_write_bits(s, (unsigned int) bits, nbits);
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nz = 0;
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}
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}
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if (block->len < 64) {
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jpec_huff_write_bits(s, jpec_ac_code[0x00], jpec_ac_len[0x00]); /* EOB marker */
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}
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}
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/* Write n bits into the JPEG buffer, with 0 < n <= 16.
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*
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* == Details
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* - 16 bits are large enough to hold any zig-zag coeff or the longest AC code
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* - bits are chunked into bytes before being written into the JPEG buffer
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* - any remaining bits are kept in memory by the Huffman state
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* - at most 7 bits can be kept in memory
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* - a 32-bit integer buffer is used internally
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* - only the right 24 bits part of this buffer are used
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* - the input bits and remaining bits (if any) are left-justified on this part
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* - a mask is used to mask off any extra bits: useful when the input value has been
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* first transformed by bitwise complement(|initial value|)
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* - if an 0xFF byte is detected a 0x00 stuff byte is automatically written right after
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*/
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static void jpec_huff_write_bits(jpec_huff_state_t *s, unsigned int bits, int n) {
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assert(s && n > 0 && n <= 16);
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int32_t mask = (((int32_t) 1) << n) - 1;
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int32_t buffer = (int32_t) bits;
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int nbits = s->nbits + n;
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buffer &= mask;
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buffer <<= 24 - nbits;
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buffer |= s->buffer;
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while (nbits >= 8) {
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int chunk = (int) ((buffer >> 16) & 0xFF);
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jpec_buffer_write_byte(s->buf, chunk);
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if (chunk == 0xFF) jpec_buffer_write_byte(s->buf, 0x00);
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buffer <<= 8;
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nbits -= 8;
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}
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s->buffer = buffer;
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s->nbits = nbits;
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}
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