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1 /*
2 LodePNG Utils
3 
4 Copyright (c) 2005-2012 Lode Vandevenne
5 
6 This software is provided 'as-is', without any express or implied
7 warranty. In no event will the authors be held liable for any damages
8 arising from the use of this software.
9 
10 Permission is granted to anyone to use this software for any purpose,
11 including commercial applications, and to alter it and redistribute it
12 freely, subject to the following restrictions:
13 
14     1. The origin of this software must not be misrepresented; you must not
15     claim that you wrote the original software. If you use this software
16     in a product, an acknowledgment in the product documentation would be
17     appreciated but is not required.
18 
19     2. Altered source versions must be plainly marked as such, and must not be
20     misrepresented as being the original software.
21 
22     3. This notice may not be removed or altered from any source
23     distribution.
24 */
25 
26 /*
27 Extra C++ utilities for LodePNG, for convenience.
28 */
29 
30 #include <string>
31 #include <vector>
32 #include "lodepng.h"
33 
34 #pragma once
35 
36 namespace lodepng
37 {
38 
39 /*
40 Returns info from the header of the PNG by value, purely for convenience.
41 Does NOT check for errors. Returns bogus info if the PNG has an error.
42 Does not require cleanup of allocated memory because no palette or text chunk
43 info is in the LodePNGInfo object after checking only the header of the PNG.
44 */
45 LodePNGInfo getPNGHeaderInfo(const std::vector<unsigned char>& png);
46 
47 /*
48 Get the names and sizes of all chunks in the PNG file.
49 Returns 0 if ok, non-0 if error happened.
50 */
51 unsigned getChunkInfo(std::vector<std::string>& names, std::vector<size_t>& sizes,
52                       const std::vector<unsigned char>& png);
53 
54 /*
55 Returns the names and full chunks (including the name and everything else that
56 makes up the chunk) for all chunks except IHDR, PLTE, IDAT and IEND.
57 It separates the chunks into 3 separate lists, representing the chunks between
58 certain critical chunks: 0: IHDR-PLTE, 1: PLTE-IDAT, 2: IDAT-IEND
59 Returns 0 if ok, non-0 if error happened.
60 */
61 unsigned getChunks(std::vector<std::string> names[3],
62                    std::vector<std::vector<unsigned char> > chunks[3],
63                    const std::vector<unsigned char>& png);
64 
65 /*
66 Inserts chunks into the given png file. The chunks must be fully encoded,
67 including length, type, content and CRC.
68 The array index determines where it goes:
69 0: between IHDR and PLTE, 1: between PLTE and IDAT, 2: between IDAT and IEND.
70 They're appended at the end of those locations within the PNG.
71 Returns 0 if ok, non-0 if error happened.
72 */
73 unsigned insertChunks(std::vector<unsigned char>& png,
74                       const std::vector<std::vector<unsigned char> > chunks[3]);
75 
76 /*
77 Get the filtertypes of each scanline in this PNG file.
78 Returns 0 if ok, 1 if PNG decoding error happened.
79 
80 For a non-interlaced PNG, it returns one filtertype per scanline, in order.
81 
82 For interlaced PNGs, it returns a result as if it's not interlaced. It returns
83 one filtertype per scanline, in order. The values match pass 6 and 7 of the
84 Adam7 interlacing, alternating between the two, so that the values correspond
85 the most to their scanlines.
86 */
87 unsigned getFilterTypes(std::vector<unsigned char>& filterTypes, const std::vector<unsigned char>& png);
88 
89 /*
90 Get the filtertypes of each scanline in every interlace pass this PNG file.
91 Returns 0 if ok, 1 if PNG decoding error happened.
92 
93 For a non-interlaced PNG, it returns one filtertype per scanline, in order, in
94 a single std::vector in filterTypes.
95 
96 For an interlaced PNG, it returns 7 std::vectors in filterTypes, one for each
97 Adam7 pass. The amount of values per pass can be calculated as follows, where
98 w and h are the size of the image and all divisions are integer divisions:
99 pass 1: (h + 7) / 8
100 pass 2: w <= 4 ? 0 : (h + 7) / 8
101 pass 3: h <= 4 ? 0 : (h + 7) / 8
102 pass 4: w <= 2 ? 0 : (h + 3) / 4
103 pass 5: h <= 2 ? 0 : (h + 3) / 4
104 pass 6: w <= 1 ? 0 : (h + 1) / 2
105 pass 7: h <= 1 ? 0 : (h + 1) / 2
106 */
107 unsigned getFilterTypesInterlaced(std::vector<std::vector<unsigned char> >& filterTypes,
108                                   const std::vector<unsigned char>& png);
109 
110 /*
111 Returns the value of the i-th pixel in an image with 1, 2, 4 or 8-bit color.
112 E.g. if bits is 4 and i is 5, it returns the 5th nibble (4-bit group), which
113 is the second half of the 3th byte, in big endian (PNG's endian order).
114 */
115 int getPaletteValue(const unsigned char* data, size_t i, int bits);
116 
117 /*
118 The information for extractZlibInfo.
119 */
120 struct ZlibBlockInfo
121 {
122   int btype; //block type (0-2)
123   size_t compressedbits; //size of compressed block in bits
124   size_t uncompressedbytes; //size of uncompressed block in bytes
125 
126   // only filled in for block type 2
127   size_t treebits; //encoded tree size in bits
128   int hlit; //the HLIT value that was filled in for this tree
129   int hdist; //the HDIST value that was filled in for this tree
130   int hclen; //the HCLEN value that was filled in for this tree
131   std::vector<int> clcl; //19 code length code lengths (compressed tree's tree)
132   std::vector<int> treecodes; //N tree codes, with values 0-18. Values 17 or 18 are followed by the repetition value.
133   std::vector<int> litlenlengths; //288 code lengths for lit/len symbols
134   std::vector<int> distlengths; //32 code lengths for dist symbols
135 
136   // only filled in for block types 1 or 2
137   std::vector<int> lz77_lcode; //LZ77 codes. 0-255: literals. 256: end symbol. 257-285: length code of length/dist pairs
138   // the next vectors have the same size as lz77_lcode, but an element only has meaningful value if lz77_lcode contains a length code.
139   std::vector<int> lz77_dcode;
140   std::vector<int> lz77_lbits;
141   std::vector<int> lz77_dbits;
142   std::vector<int> lz77_lvalue;
143   std::vector<int> lz77_dvalue;
144   size_t numlit; //number of lit codes in this block
145   size_t numlen; //number of len codes in this block
146 };
147 
148 //Extracts all info needed from a PNG file to reconstruct the zlib compression exactly.
149 void extractZlibInfo(std::vector<ZlibBlockInfo>& zlibinfo, const std::vector<unsigned char>& in);
150 
151 } // namespace lodepng
152