169 lines
5.2 KiB
C++
169 lines
5.2 KiB
C++
/*
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* This file contains code to decompress the LZW encoded animated GIF data
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*
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* Written by: Craig A. Lindley, Fabrice Bellard and Steven A. Bennett
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* See my book, "Practical Image Processing in C", John Wiley & Sons, Inc.
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*
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* Copyright (c) 2014 Craig A. Lindley
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* Minor modifications by Louis Beaudoin (pixelmatix)
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy of
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* this software and associated documentation files (the "Software"), to deal in
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* the Software without restriction, including without limitation the rights to
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* use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
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* the Software, and to permit persons to whom the Software is furnished to do so,
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* subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in all
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* 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, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
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* FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
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* COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
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* IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
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* CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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*/
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#define LZWDEBUG 0
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#include "GifDecoder.h"
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template <int maxGifWidth, int maxGifHeight, int lzwMaxBits>
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void GifDecoder<maxGifWidth, maxGifHeight, lzwMaxBits>::lzw_setTempBuffer(uint8_t * tempBuffer) {
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temp_buffer = tempBuffer;
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}
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// Initialize LZW decoder
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// csize initial code size in bits
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// buf input data
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template <int maxGifWidth, int maxGifHeight, int lzwMaxBits>
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void GifDecoder<maxGifWidth, maxGifHeight, lzwMaxBits>::lzw_decode_init (int csize) {
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// Initialize read buffer variables
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bbuf = 0;
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bbits = 0;
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bs = 0;
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bcnt = 0;
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// Initialize decoder variables
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codesize = csize;
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cursize = codesize + 1;
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curmask = mask[cursize];
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top_slot = 1 << cursize;
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clear_code = 1 << codesize;
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end_code = clear_code + 1;
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slot = newcodes = clear_code + 2;
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oc = fc = -1;
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sp = stack;
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}
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// Get one code of given number of bits from stream
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template <int maxGifWidth, int maxGifHeight, int lzwMaxBits>
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int GifDecoder<maxGifWidth, maxGifHeight, lzwMaxBits>::lzw_get_code() {
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while (bbits < cursize) {
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if (bcnt == bs) {
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// get number of bytes in next block
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readIntoBuffer(temp_buffer, 1);
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bs = temp_buffer[0];
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readIntoBuffer(temp_buffer, bs);
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bcnt = 0;
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}
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bbuf |= temp_buffer[bcnt] << bbits;
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bbits += 8;
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bcnt++;
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}
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int c = bbuf;
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bbuf >>= cursize;
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bbits -= cursize;
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return c & curmask;
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}
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// Decode given number of bytes
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// buf 8 bit output buffer
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// len number of pixels to decode
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// returns the number of bytes decoded
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template <int maxGifWidth, int maxGifHeight, int lzwMaxBits>
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int GifDecoder<maxGifWidth, maxGifHeight, lzwMaxBits>::lzw_decode(uint8_t *buf, int len, uint8_t *bufend) {
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int l, c, code;
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#if LZWDEBUG == 1
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unsigned char debugMessagePrinted = 0;
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#endif
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if (end_code < 0) {
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return 0;
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}
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l = len;
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for (;;) {
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while (sp > stack) {
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// load buf with data if we're still within bounds
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if(buf < bufend) {
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*buf++ = *(--sp);
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} else {
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// out of bounds, keep incrementing the pointers, but don't use the data
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#if LZWDEBUG == 1
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// only print this message once per call to lzw_decode
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if(buf == bufend)
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Serial.println("****** LZW imageData buffer overrun *******");
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#endif
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}
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if ((--l) == 0) {
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return len;
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}
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}
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c = lzw_get_code();
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if (c == end_code) {
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break;
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}
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else if (c == clear_code) {
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cursize = codesize + 1;
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curmask = mask[cursize];
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slot = newcodes;
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top_slot = 1 << cursize;
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fc= oc= -1;
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}
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else {
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code = c;
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if ((code == slot) && (fc >= 0)) {
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*sp++ = fc;
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code = oc;
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}
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else if (code >= slot) {
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break;
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}
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while (code >= newcodes) {
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*sp++ = suffix[code];
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code = prefix[code];
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}
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*sp++ = code;
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if ((slot < top_slot) && (oc >= 0)) {
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suffix[slot] = code;
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prefix[slot++] = oc;
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}
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fc = code;
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oc = c;
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if (slot >= top_slot) {
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if (cursize < lzwMaxBits) {
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top_slot <<= 1;
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curmask = mask[++cursize];
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} else {
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#if LZWDEBUG == 1
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if(!debugMessagePrinted) {
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debugMessagePrinted = 1;
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Serial.println("****** cursize >= lzwMaxBits *******");
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}
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#endif
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}
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}
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}
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}
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end_code = -1;
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return len - l;
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}
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