add example and dev files to LodePNG repository

1 files changed, 151 insertions, 0 deletions

diff --git a/lodepng_util.h b/lodepng_util.h
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+/*
+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.
+*/
+
+/*
+Extra C++ utilities for LodePNG, for convenience.
+*/
+
+#include <string>
+#include <vector>
+#include "lodepng.h"
+
+#pragma once
+
+namespace lodepng
+{
+
+/*
+Returns info from the header of the PNG by value, purely for convenience.
+Does NOT check for errors. Returns bogus info if the PNG has an error.
+Does not require cleanup of allocated memory because no palette or text chunk
+info is in the LodePNGInfo object after checking only the header of the PNG.
+*/
+LodePNGInfo getPNGHeaderInfo(const std::vector<unsigned char>& png);
+
+/*
+Get the names and sizes of all chunks in the PNG file.
+Returns 0 if ok, non-0 if error happened.
+*/
+unsigned getChunkInfo(std::vector<std::string>& names, std::vector<size_t>& sizes,
+                      const std::vector<unsigned char>& png);
+
+/*
+Returns the names and full chunks (including the name and everything else that
+makes up the chunk) for all chunks except IHDR, PLTE, IDAT and IEND.
+It separates the chunks into 3 separate lists, representing the chunks between
+certain critical chunks: 0: IHDR-PLTE, 1: PLTE-IDAT, 2: IDAT-IEND
+Returns 0 if ok, non-0 if error happened.
+*/
+unsigned getChunks(std::vector<std::string> names[3],
+                   std::vector<std::vector<unsigned char> > chunks[3],
+                   const std::vector<unsigned char>& png);
+
+/*
+Inserts chunks into the given png file. The chunks must be fully encoded,
+including length, type, content and CRC.
+The array index determines where it goes:
+0: between IHDR and PLTE, 1: between PLTE and IDAT, 2: between IDAT and IEND.
+They're appended at the end of those locations within the PNG.
+Returns 0 if ok, non-0 if error happened.
+*/
+unsigned insertChunks(std::vector<unsigned char>& png,
+                      const std::vector<std::vector<unsigned char> > chunks[3]);
+
+/*
+Get the filtertypes of each scanline in this PNG file.
+Returns 0 if ok, 1 if PNG decoding error happened.
+
+For a non-interlaced PNG, it returns one filtertype per scanline, in order.
+
+For interlaced PNGs, it returns a result as if it's not interlaced. It returns
+one filtertype per scanline, in order. The values match pass 6 and 7 of the
+Adam7 interlacing, alternating between the two, so that the values correspond
+the most to their scanlines.
+*/
+unsigned getFilterTypes(std::vector<unsigned char>& filterTypes, const std::vector<unsigned char>& png);
+
+/*
+Get the filtertypes of each scanline in every interlace pass this PNG file.
+Returns 0 if ok, 1 if PNG decoding error happened.
+
+For a non-interlaced PNG, it returns one filtertype per scanline, in order, in
+a single std::vector in filterTypes.
+
+For an interlaced PNG, it returns 7 std::vectors in filterTypes, one for each
+Adam7 pass. The amount of values per pass can be calculated as follows, where
+w and h are the size of the image and all divisions are integer divisions:
+pass 1: (h + 7) / 8
+pass 2: w <= 4 ? 0 : (h + 7) / 8
+pass 3: h <= 4 ? 0 : (h + 7) / 8
+pass 4: w <= 2 ? 0 : (h + 3) / 4
+pass 5: h <= 2 ? 0 : (h + 3) / 4
+pass 6: w <= 1 ? 0 : (h + 1) / 2
+pass 7: h <= 1 ? 0 : (h + 1) / 2
+*/
+unsigned getFilterTypesInterlaced(std::vector<std::vector<unsigned char> >& filterTypes,
+                                  const std::vector<unsigned char>& png);
+
+/*
+Returns the value of the i-th pixel in an image with 1, 2, 4 or 8-bit color.
+E.g. if bits is 4 and i is 5, it returns the 5th nibble (4-bit group), which
+is the second half of the 3th byte, in big endian (PNG's endian order).
+*/
+int getPaletteValue(const unsigned char* data, size_t i, int bits);
+
+/*
+The information for extractZlibInfo.
+*/
+struct ZlibBlockInfo
+{
+  int btype; //block type (0-2)
+  size_t compressedbits; //size of compressed block in bits
+  size_t uncompressedbytes; //size of uncompressed block in bytes
+
+  // only filled in for block type 2
+  size_t treebits; //encoded tree size in bits
+  int hlit; //the HLIT value that was filled in for this tree
+  int hdist; //the HDIST value that was filled in for this tree
+  int hclen; //the HCLEN value that was filled in for this tree
+  std::vector<int> clcl; //19 code length code lengths (compressed tree's tree)
+  std::vector<int> treecodes; //N tree codes, with values 0-18. Values 17 or 18 are followed by the repetition value.
+  std::vector<int> litlenlengths; //288 code lengths for lit/len symbols
+  std::vector<int> distlengths; //32 code lengths for dist symbols
+
+  // only filled in for block types 1 or 2
+  std::vector<int> lz77_lcode; //LZ77 codes. 0-255: literals. 256: end symbol. 257-285: length code of length/dist pairs
+  // the next vectors have the same size as lz77_lcode, but an element only has meaningful value if lz77_lcode contains a length code.
+  std::vector<int> lz77_dcode;
+  std::vector<int> lz77_lbits;
+  std::vector<int> lz77_dbits;
+  std::vector<int> lz77_lvalue;
+  std::vector<int> lz77_dvalue;
+  size_t numlit; //number of lit codes in this block
+  size_t numlen; //number of len codes in this block
+};
+
+//Extracts all info needed from a PNG file to reconstruct the zlib compression exactly.
+void extractZlibInfo(std::vector<ZlibBlockInfo>& zlibinfo, const std::vector<unsigned char>& in);
+
+} // namespace lodepng