From ad8aab2a14a7b4dc01e33312d151b6f535f3c41e Mon Sep 17 00:00:00 2001 From: Lode Date: Sun, 24 Aug 2014 20:09:39 +0200 Subject: add example and dev files to LodePNG repository --- lodepng_util.cpp | 653 +++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 653 insertions(+) create mode 100644 lodepng_util.cpp (limited to 'lodepng_util.cpp') diff --git a/lodepng_util.cpp b/lodepng_util.cpp new file mode 100644 index 0000000..3784b6e --- /dev/null +++ b/lodepng_util.cpp @@ -0,0 +1,653 @@ +/* +LodePNG Utils + +Copyright (c) 2005-2014 Lode Vandevenne + +This software is provided 'as-is', without any express or implied +warranty. In no event will the authors be held liable for any damages +arising from the use of this software. + +Permission is granted to anyone to use this software for any purpose, +including commercial applications, and to alter it and redistribute it +freely, subject to the following restrictions: + + 1. The origin of this software must not be misrepresented; you must not + claim that you wrote the original software. If you use this software + in a product, an acknowledgment in the product documentation would be + appreciated but is not required. + + 2. Altered source versions must be plainly marked as such, and must not be + misrepresented as being the original software. + + 3. This notice may not be removed or altered from any source + distribution. +*/ + +#include "lodepng_util.h" +#include + +namespace lodepng +{ + +LodePNGInfo getPNGHeaderInfo(const std::vector& png) +{ + unsigned w, h; + lodepng::State state; + lodepng_inspect(&w, &h, &state, &png[0], png.size()); + return state.info_png; +} + +unsigned getChunkInfo(std::vector& names, std::vector& sizes, + const std::vector& png) +{ + // Listing chunks is based on the original file, not the decoded png info. + const unsigned char *chunk, *begin, *end; + end = &png.back() + 1; + begin = chunk = &png.front() + 8; + + while(chunk + 8 < end && chunk >= begin) + { + char type[5]; + lodepng_chunk_type(type, chunk); + if(std::string(type).size() != 4) return 1; + + names.push_back(type); + sizes.push_back(lodepng_chunk_length(chunk)); + + chunk = lodepng_chunk_next_const(chunk); + } + return 0; +} + +unsigned getChunks(std::vector names[3], + std::vector > chunks[3], + const std::vector& png) +{ + const unsigned char *chunk, *next, *begin, *end; + end = &png.back() + 1; + begin = chunk = &png.front() + 8; + + int location = 0; + + while(chunk + 8 < end && chunk >= begin) + { + char type[5]; + lodepng_chunk_type(type, chunk); + std::string name(type); + if(name.size() != 4) return 1; + + next = lodepng_chunk_next_const(chunk); + + if(name == "IHDR") + { + location = 0; + } + else if(name == "PLTE") + { + location = 1; + } + else if(name == "IDAT") + { + location = 2; + } + else if(name != "IEND") + { + names[location].push_back(name); + chunks[location].push_back(std::vector(chunk, next)); + } + + chunk = next; + } + return 0; +} + + +unsigned insertChunks(std::vector& png, + const std::vector > chunks[3]) +{ + const unsigned char *chunk, *next, *begin, *end; + end = &png.back() + 1; + begin = chunk = &png.front() + 8; + + long l0 = 0; //location 0: IHDR-l0-PLTE (or IHDR-l0-l1-IDAT) + long l1 = 0; //location 1: PLTE-l1-IDAT (or IHDR-l0-l1-IDAT) + long l2 = 0; //location 2: IDAT-l2-IEND + + while(chunk + 8 < end && chunk >= begin) + { + char type[5]; + lodepng_chunk_type(type, chunk); + std::string name(type); + if(name.size() != 4) return 1; + + next = lodepng_chunk_next_const(chunk); + + if(name == "PLTE") + { + if(l0 == 0) l0 = chunk - begin + 8; + } + else if(name == "IDAT") + { + if(l0 == 0) l0 = chunk - begin + 8; + if(l1 == 0) l1 = chunk - begin + 8; + } + else if(name == "IEND") + { + if(l2 == 0) l2 = chunk - begin + 8; + } + + chunk = next; + } + + std::vector result; + result.insert(result.end(), png.begin(), png.begin() + l0); + for(size_t i = 0; i < chunks[0].size(); i++) result.insert(result.end(), chunks[0][i].begin(), chunks[0][i].end()); + result.insert(result.end(), png.begin() + l0, png.begin() + l1); + for(size_t i = 0; i < chunks[1].size(); i++) result.insert(result.end(), chunks[1][i].begin(), chunks[1][i].end()); + result.insert(result.end(), png.begin() + l1, png.begin() + l2); + for(size_t i = 0; i < chunks[2].size(); i++) result.insert(result.end(), chunks[2][i].begin(), chunks[2][i].end()); + result.insert(result.end(), png.begin() + l2, png.end()); + + png = result; + return 0; +} + +unsigned getFilterTypesInterlaced(std::vector >& filterTypes, + const std::vector& png) +{ + //Get color type and interlace type + lodepng::State state; + unsigned w, h; + unsigned error; + error = lodepng_inspect(&w, &h, &state, &png[0], png.size()); + + if(error) return 1; + + //Read literal data from all IDAT chunks + const unsigned char *chunk, *begin, *end; + end = &png.back() + 1; + begin = chunk = &png.front() + 8; + + std::vector zdata; + + while(chunk + 8 < end && chunk >= begin) + { + char type[5]; + lodepng_chunk_type(type, chunk); + if(std::string(type).size() != 4) return 1; //Probably not a PNG file + + if(std::string(type) == "IDAT") + { + const unsigned char* cdata = lodepng_chunk_data_const(chunk); + unsigned clength = lodepng_chunk_length(chunk); + + for(unsigned i = 0; i < clength; i++) + { + zdata.push_back(cdata[i]); + } + } + + chunk = lodepng_chunk_next_const(chunk); + } + + //Decompress all IDAT data + std::vector data; + error = lodepng::decompress(data, &zdata[0], zdata.size()); + + if(error) return 1; + + if(state.info_png.interlace_method == 0) + { + filterTypes.resize(1); + + //A line is 1 filter byte + all pixels + size_t linebytes = 1 + lodepng_get_raw_size(w, 1, &state.info_png.color); + + for(size_t i = 0; i < data.size(); i += linebytes) + { + filterTypes[0].push_back(data[i]); + } + } + else + { + //Interlaced + filterTypes.resize(7); + static const unsigned ADAM7_IX[7] = { 0, 4, 0, 2, 0, 1, 0 }; /*x start values*/ + static const unsigned ADAM7_IY[7] = { 0, 0, 4, 0, 2, 0, 1 }; /*y start values*/ + static const unsigned ADAM7_DX[7] = { 8, 8, 4, 4, 2, 2, 1 }; /*x delta values*/ + static const unsigned ADAM7_DY[7] = { 8, 8, 8, 4, 4, 2, 2 }; /*y delta values*/ + size_t pos = 0; + for(size_t j = 0; j < 7; j++) + { + unsigned w2 = (w - ADAM7_IX[j] + ADAM7_DX[j] - 1) / ADAM7_DX[j]; + unsigned h2 = (h - ADAM7_IY[j] + ADAM7_DY[j] - 1) / ADAM7_DY[j]; + if(ADAM7_IX[j] >= w || ADAM7_IY[j] >= h) w2 = h2 = 0; + size_t linebytes = 1 + lodepng_get_raw_size(w2, 1, &state.info_png.color); + for(size_t i = 0; i < h2; i++) + { + filterTypes[j].push_back(data[pos]); + pos += linebytes; + } + } + } + return 0; /* OK */ +} + + +unsigned getFilterTypes(std::vector& filterTypes, const std::vector& png) +{ + std::vector > passes; + unsigned error = getFilterTypesInterlaced(passes, png); + if(error) return error; + + if(passes.size() == 1) + { + filterTypes.swap(passes[0]); + } + else + { + lodepng::State state; + unsigned w, h; + lodepng_inspect(&w, &h, &state, &png[0], png.size()); + /* + Interlaced. Simplify it: put pass 6 and 7 alternating in the one vector so + that one filter per scanline of the uninterlaced image is given, with that + filter corresponding the closest to what it would be for non-interlaced + image. + */ + for(size_t i = 0; i < h; i++) + { + filterTypes.push_back(i % 2 == 0 ? passes[5][i / 2] : passes[6][i / 2]); + } + } + return 0; /* OK */ +} + +int getPaletteValue(const unsigned char* data, size_t i, int bits) +{ + if(bits == 8) return data[i]; + else if(bits == 4) return (data[i / 2] >> ((i % 2) * 4)) & 15; + else if(bits == 2) return (data[i / 4] >> ((i % 4) * 2)) & 3; + else if(bits == 1) return (data[i / 8] >> (i % 8)) & 1; + else return 0; +} + +//This uses a stripped down version of picoPNG to extract detailed zlib information while decompressing. +static const unsigned long LENBASE[29] = + {3,4,5,6,7,8,9,10,11,13,15,17,19,23,27,31,35,43,51,59,67,83,99,115,131,163,195,227,258}; +static const unsigned long LENEXTRA[29] = + {0,0,0,0,0,0,0, 0, 1, 1, 1, 1, 2, 2, 2, 2, 3, 3, 3, 3, 4, 4, 4, 4, 5, 5, 5, 5, 0}; +static const unsigned long DISTBASE[30] = + {1,2,3,4,5,7,9,13,17,25,33,49,65,97,129,193,257,385,513,769,1025,1537,2049,3073,4097,6145,8193,12289,16385,24577}; +static const unsigned long DISTEXTRA[30] = + {0,0,0,0,1,1,2, 2, 3, 3, 4, 4, 5, 5, 6, 6, 7, 7, 8, 8, 9, 9, 10, 10, 11, 11, 12, 12, 13, 13}; +static const unsigned long CLCL[19] = + {16, 17, 18, 0, 8, 7, 9, 6, 10, 5, 11, 4, 12, 3, 13, 2, 14, 1, 15}; //code length code lengths + +struct ExtractZlib // Zlib decompression and information extraction +{ + std::vector* zlibinfo; + ExtractZlib(std::vector* info) : zlibinfo(info) {}; + int error; + + unsigned long readBitFromStream(size_t& bitp, const unsigned char* bits) + { + unsigned long result = (bits[bitp >> 3] >> (bitp & 0x7)) & 1; + bitp++; + return result; + } + + unsigned long readBitsFromStream(size_t& bitp, const unsigned char* bits, size_t nbits) + { + unsigned long result = 0; + for(size_t i = 0; i < nbits; i++) result += (readBitFromStream(bitp, bits)) << i; + return result; + } + + struct HuffmanTree + { + int makeFromLengths(const std::vector& bitlen, unsigned long maxbitlen) + { //make tree given the lengths + unsigned long numcodes = (unsigned long)(bitlen.size()), treepos = 0, nodefilled = 0; + std::vector tree1d(numcodes), blcount(maxbitlen + 1, 0), nextcode(maxbitlen + 1, 0); + //count number of instances of each code length + for(unsigned long bits = 0; bits < numcodes; bits++) blcount[bitlen[bits]]++; + for(unsigned long bits = 1; bits <= maxbitlen; bits++) + { + nextcode[bits] = (nextcode[bits - 1] + blcount[bits - 1]) << 1; + } + //generate all the codes + for(unsigned long n = 0; n < numcodes; n++) if(bitlen[n] != 0) tree1d[n] = nextcode[bitlen[n]]++; + tree2d.clear(); tree2d.resize(numcodes * 2, 32767); //32767 here means the tree2d isn't filled there yet + for(unsigned long n = 0; n < numcodes; n++) //the codes + for(unsigned long i = 0; i < bitlen[n]; i++) //the bits for this code + { + unsigned long bit = (tree1d[n] >> (bitlen[n] - i - 1)) & 1; + if(treepos > numcodes - 2) return 55; + if(tree2d[2 * treepos + bit] == 32767) //not yet filled in + { + if(i + 1 == bitlen[n]) + { + //last bit + tree2d[2 * treepos + bit] = n; + treepos = 0; + } + else + { + //addresses are encoded as values > numcodes + tree2d[2 * treepos + bit] = ++nodefilled + numcodes; + treepos = nodefilled; + } + } + else treepos = tree2d[2 * treepos + bit] - numcodes; //subtract numcodes from address to get address value + } + return 0; + } + int decode(bool& decoded, unsigned long& result, size_t& treepos, unsigned long bit) const + { //Decodes a symbol from the tree + unsigned long numcodes = (unsigned long)tree2d.size() / 2; + if(treepos >= numcodes) return 11; //error: you appeared outside the codetree + result = tree2d[2 * treepos + bit]; + decoded = (result < numcodes); + treepos = decoded ? 0 : result - numcodes; + return 0; + } + //2D representation of a huffman tree: one dimension is "0" or "1", the other contains all nodes and leaves. + std::vector tree2d; + }; + + void inflate(std::vector& out, const std::vector& in, size_t inpos = 0) + { + size_t bp = 0, pos = 0; //bit pointer and byte pointer + error = 0; + unsigned long BFINAL = 0; + while(!BFINAL && !error) + { + size_t uncomprblockstart = pos; + size_t bpstart = bp; + if(bp >> 3 >= in.size()) { error = 52; return; } //error, bit pointer will jump past memory + BFINAL = readBitFromStream(bp, &in[inpos]); + unsigned long BTYPE = readBitFromStream(bp, &in[inpos]); BTYPE += 2 * readBitFromStream(bp, &in[inpos]); + zlibinfo->resize(zlibinfo->size() + 1); + zlibinfo->back().btype = BTYPE; + if(BTYPE == 3) { error = 20; return; } //error: invalid BTYPE + else if(BTYPE == 0) inflateNoCompression(out, &in[inpos], bp, pos, in.size()); + else inflateHuffmanBlock(out, &in[inpos], bp, pos, in.size(), BTYPE); + size_t uncomprblocksize = pos - uncomprblockstart; + zlibinfo->back().compressedbits = bp - bpstart; + zlibinfo->back().uncompressedbytes = uncomprblocksize; + } + } + + void generateFixedTrees(HuffmanTree& tree, HuffmanTree& treeD) //get the tree of a deflated block with fixed tree + { + std::vector bitlen(288, 8), bitlenD(32, 5);; + for(size_t i = 144; i <= 255; i++) bitlen[i] = 9; + for(size_t i = 256; i <= 279; i++) bitlen[i] = 7; + tree.makeFromLengths(bitlen, 15); + treeD.makeFromLengths(bitlenD, 15); + } + + //the code tree for Huffman codes, dist codes, and code length codes + HuffmanTree codetree, codetreeD, codelengthcodetree; + unsigned long huffmanDecodeSymbol(const unsigned char* in, size_t& bp, const HuffmanTree& tree, size_t inlength) + { + //decode a single symbol from given list of bits with given code tree. return value is the symbol + bool decoded; unsigned long ct; + for(size_t treepos = 0;;) + { + if((bp & 0x07) == 0 && (bp >> 3) > inlength) { error = 10; return 0; } //error: end reached without endcode + error = tree.decode(decoded, ct, treepos, readBitFromStream(bp, in)); + if(error) return 0; //stop, an error happened + if(decoded) return ct; + } + } + + void getTreeInflateDynamic(HuffmanTree& tree, HuffmanTree& treeD, + const unsigned char* in, size_t& bp, size_t inlength) + { + size_t bpstart = bp; + //get the tree of a deflated block with dynamic tree, the tree itself is also Huffman compressed with a known tree + std::vector bitlen(288, 0), bitlenD(32, 0); + if(bp >> 3 >= inlength - 2) { error = 49; return; } //the bit pointer is or will go past the memory + size_t HLIT = readBitsFromStream(bp, in, 5) + 257; //number of literal/length codes + 257 + size_t HDIST = readBitsFromStream(bp, in, 5) + 1; //number of dist codes + 1 + size_t HCLEN = readBitsFromStream(bp, in, 4) + 4; //number of code length codes + 4 + zlibinfo->back().hlit = HLIT - 257; + zlibinfo->back().hdist = HDIST - 1; + zlibinfo->back().hclen = HCLEN - 4; + std::vector codelengthcode(19); //lengths of tree to decode the lengths of the dynamic tree + for(size_t i = 0; i < 19; i++) codelengthcode[CLCL[i]] = (i < HCLEN) ? readBitsFromStream(bp, in, 3) : 0; + //code length code lengths + for(size_t i = 0; i < codelengthcode.size(); i++) zlibinfo->back().clcl.push_back(codelengthcode[i]); + error = codelengthcodetree.makeFromLengths(codelengthcode, 7); if(error) return; + size_t i = 0, replength; + while(i < HLIT + HDIST) + { + unsigned long code = huffmanDecodeSymbol(in, bp, codelengthcodetree, inlength); if(error) return; + zlibinfo->back().treecodes.push_back(code); //tree symbol code + if(code <= 15) { if(i < HLIT) bitlen[i++] = code; else bitlenD[i++ - HLIT] = code; } //a length code + else if(code == 16) //repeat previous + { + if(bp >> 3 >= inlength) { error = 50; return; } //error, bit pointer jumps past memory + replength = 3 + readBitsFromStream(bp, in, 2); + unsigned long value; //set value to the previous code + if((i - 1) < HLIT) value = bitlen[i - 1]; + else value = bitlenD[i - HLIT - 1]; + for(size_t n = 0; n < replength; n++) //repeat this value in the next lengths + { + if(i >= HLIT + HDIST) { error = 13; return; } //error: i is larger than the amount of codes + if(i < HLIT) bitlen[i++] = value; else bitlenD[i++ - HLIT] = value; + } + } + else if(code == 17) //repeat "0" 3-10 times + { + if(bp >> 3 >= inlength) { error = 50; return; } //error, bit pointer jumps past memory + replength = 3 + readBitsFromStream(bp, in, 3); + zlibinfo->back().treecodes.push_back(replength); //tree symbol code repetitions + for(size_t n = 0; n < replength; n++) //repeat this value in the next lengths + { + if(i >= HLIT + HDIST) { error = 14; return; } //error: i is larger than the amount of codes + if(i < HLIT) bitlen[i++] = 0; else bitlenD[i++ - HLIT] = 0; + } + } + else if(code == 18) //repeat "0" 11-138 times + { + if(bp >> 3 >= inlength) { error = 50; return; } //error, bit pointer jumps past memory + replength = 11 + readBitsFromStream(bp, in, 7); + zlibinfo->back().treecodes.push_back(replength); //tree symbol code repetitions + for(size_t n = 0; n < replength; n++) //repeat this value in the next lengths + { + if(i >= HLIT + HDIST) { error = 15; return; } //error: i is larger than the amount of codes + if(i < HLIT) bitlen[i++] = 0; else bitlenD[i++ - HLIT] = 0; + } + } + else { error = 16; return; } //error: somehow an unexisting code appeared. This can never happen. + } + if(bitlen[256] == 0) { error = 64; return; } //the length of the end code 256 must be larger than 0 + error = tree.makeFromLengths(bitlen, 15); + if(error) return; //now we've finally got HLIT and HDIST, so generate the code trees, and the function is done + error = treeD.makeFromLengths(bitlenD, 15); + if(error) return; + zlibinfo->back().treebits = bp - bpstart; + //lit/len/end symbol lengths + for(size_t j = 0; j < bitlen.size(); j++) zlibinfo->back().litlenlengths.push_back(bitlen[j]); + //dist lengths + for(size_t j = 0; j < bitlenD.size(); j++) zlibinfo->back().distlengths.push_back(bitlenD[j]); + } + + void inflateHuffmanBlock(std::vector& out, + const unsigned char* in, size_t& bp, size_t& pos, size_t inlength, unsigned long btype) + { + size_t numcodes = 0, numlit = 0, numlen = 0; //for logging + if(btype == 1) { generateFixedTrees(codetree, codetreeD); } + else if(btype == 2) { getTreeInflateDynamic(codetree, codetreeD, in, bp, inlength); if(error) return; } + for(;;) + { + unsigned long code = huffmanDecodeSymbol(in, bp, codetree, inlength); if(error) return; + numcodes++; + zlibinfo->back().lz77_lcode.push_back(code); //output code + zlibinfo->back().lz77_dcode.push_back(0); + zlibinfo->back().lz77_lbits.push_back(0); + zlibinfo->back().lz77_dbits.push_back(0); + zlibinfo->back().lz77_lvalue.push_back(0); + zlibinfo->back().lz77_dvalue.push_back(0); + + if(code == 256) break; //end code + else if(code <= 255) //literal symbol + { + out.push_back((unsigned char)(code)); + pos++; + numlit++; + } + else if(code >= 257 && code <= 285) //length code + { + size_t length = LENBASE[code - 257], numextrabits = LENEXTRA[code - 257]; + if((bp >> 3) >= inlength) { error = 51; return; } //error, bit pointer will jump past memory + length += readBitsFromStream(bp, in, numextrabits); + unsigned long codeD = huffmanDecodeSymbol(in, bp, codetreeD, inlength); if(error) return; + if(codeD > 29) { error = 18; return; } //error: invalid dist code (30-31 are never used) + unsigned long dist = DISTBASE[codeD], numextrabitsD = DISTEXTRA[codeD]; + if((bp >> 3) >= inlength) { error = 51; return; } //error, bit pointer will jump past memory + dist += readBitsFromStream(bp, in, numextrabitsD); + size_t start = pos, back = start - dist; //backwards + for(size_t i = 0; i < length; i++) + { + out.push_back(out[back++]); + pos++; + if(back >= start) back = start - dist; + } + numlen++; + zlibinfo->back().lz77_dcode.back() = codeD; //output distance code + zlibinfo->back().lz77_lbits.back() = numextrabits; //output length extra bits + zlibinfo->back().lz77_dbits.back() = numextrabitsD; //output dist extra bits + zlibinfo->back().lz77_lvalue.back() = length; //output length + zlibinfo->back().lz77_dvalue.back() = dist; //output dist + } + } + zlibinfo->back().numlit = numlit; //output number of literal symbols + zlibinfo->back().numlen = numlen; //output number of length symbols + } + + void inflateNoCompression(std::vector& out, + const unsigned char* in, size_t& bp, size_t& pos, size_t inlength) + { + while((bp & 0x7) != 0) bp++; //go to first boundary of byte + size_t p = bp / 8; + if(p >= inlength - 4) { error = 52; return; } //error, bit pointer will jump past memory + unsigned long LEN = in[p] + 256u * in[p + 1], NLEN = in[p + 2] + 256u * in[p + 3]; p += 4; + if(LEN + NLEN != 65535) { error = 21; return; } //error: NLEN is not one's complement of LEN + if(p + LEN > inlength) { error = 23; return; } //error: reading outside of in buffer + for(unsigned long n = 0; n < LEN; n++) + { + out.push_back(in[p++]); //read LEN bytes of literal data + pos++; + } + bp = p * 8; + } + + int decompress(std::vector& out, const std::vector& in) //returns error value + { + if(in.size() < 2) { return 53; } //error, size of zlib data too small + //error: 256 * in[0] + in[1] must be a multiple of 31, the FCHECK value is supposed to be made that way + if((in[0] * 256 + in[1]) % 31 != 0) { return 24; } + unsigned long CM = in[0] & 15, CINFO = (in[0] >> 4) & 15, FDICT = (in[1] >> 5) & 1; + //error: only compression method 8: inflate with sliding window of 32k is supported by the PNG spec + if(CM != 8 || CINFO > 7) { return 25; } + //error: the PNG spec says about the zlib stream: "The additional flags shall not specify a preset dictionary." + if(FDICT != 0) { return 26; } + inflate(out, in, 2); + return error; //note: adler32 checksum was skipped and ignored + } +}; + +struct ExtractPNG //PNG decoding and information extraction +{ + std::vector* zlibinfo; + ExtractPNG(std::vector* info) : zlibinfo(info) {}; + int error; + void decode(const unsigned char* in, size_t size) + { + error = 0; + if(size == 0 || in == 0) { error = 48; return; } //the given data is empty + readPngHeader(&in[0], size); if(error) return; + size_t pos = 33; //first byte of the first chunk after the header + std::vector idat; //the data from idat chunks + bool IEND = false; + //loop through the chunks, ignoring unknown chunks and stopping at IEND chunk. + //IDAT data is put at the start of the in buffer + while(!IEND) + { + //error: size of the in buffer too small to contain next chunk + if(pos + 8 >= size) { error = 30; return; } + size_t chunkLength = read32bitInt(&in[pos]); pos += 4; + if(chunkLength > 2147483647) { error = 63; return; } + //error: size of the in buffer too small to contain next chunk + if(pos + chunkLength >= size) { error = 35; return; } + //IDAT chunk, containing compressed image data + if(in[pos + 0] == 'I' && in[pos + 1] == 'D' && in[pos + 2] == 'A' && in[pos + 3] == 'T') + { + idat.insert(idat.end(), &in[pos + 4], &in[pos + 4 + chunkLength]); + pos += (4 + chunkLength); + } + else if(in[pos + 0] == 'I' && in[pos + 1] == 'E' && in[pos + 2] == 'N' && in[pos + 3] == 'D') + { + pos += 4; + IEND = true; + } + else //it's not an implemented chunk type, so ignore it: skip over the data + { + pos += (chunkLength + 4); //skip 4 letters and uninterpreted data of unimplemented chunk + } + pos += 4; //step over CRC (which is ignored) + } + std::vector out; //now the out buffer will be filled + ExtractZlib zlib(zlibinfo); //decompress with the Zlib decompressor + error = zlib.decompress(out, idat); + if(error) return; //stop if the zlib decompressor returned an error + } + + //read the information from the header and store it in the Info + void readPngHeader(const unsigned char* in, size_t inlength) + { + if(inlength < 29) { error = 27; return; } //error: the data length is smaller than the length of the header + if(in[0] != 137 || in[1] != 80 || in[2] != 78 || in[3] != 71 + || in[4] != 13 || in[5] != 10 || in[6] != 26 || in[7] != 10) { error = 28; return; } //no PNG signature + //error: it doesn't start with a IHDR chunk! + if(in[12] != 'I' || in[13] != 'H' || in[14] != 'D' || in[15] != 'R') { error = 29; return; } + } + + unsigned long readBitFromReversedStream(size_t& bitp, const unsigned char* bits) + { + unsigned long result = (bits[bitp >> 3] >> (7 - (bitp & 0x7))) & 1; + bitp++; + return result; + } + + unsigned long readBitsFromReversedStream(size_t& bitp, const unsigned char* bits, unsigned long nbits) + { + unsigned long result = 0; + for(size_t i = nbits - 1; i < nbits; i--) result += ((readBitFromReversedStream(bitp, bits)) << i); + return result; + } + + void setBitOfReversedStream(size_t& bitp, unsigned char* bits, unsigned long bit) + { + bits[bitp >> 3] |= (bit << (7 - (bitp & 0x7))); bitp++; + } + + unsigned long read32bitInt(const unsigned char* buffer) + { + return (unsigned int)((buffer[0] << 24u) | (buffer[1] << 16u) | (buffer[2] << 8u) | buffer[3]); + } +}; + +void extractZlibInfo(std::vector& zlibinfo, const std::vector& in) +{ + ExtractPNG decoder(&zlibinfo); + decoder.decode(&in[0], in.size()); + + if(decoder.error) std::cout << "extract error: " << decoder.error << std::endl; +} + +} // namespace lodepng -- cgit v1.2.3