/*
Display the names and sizes of all chunks in the PNG file.
*/
void displayChunkNames(const std::vector<unsigned char>& buffer)
{
// Listing chunks is based on the original file, not the decoded png info.
const unsigned char *chunk, *begin, *end, *next;
end = &buffer.back() + 1;
begin = chunk = &buffer.front() + 8;
std::cout << std::endl << "Chunks:" << std::endl;
std::cout << " type: length(s)";
std::string last_type;
while(chunk + 8 < end && chunk >= begin)
{
char type[5];
lodepng_chunk_type(type, chunk);
if(std::string(type).size() != 4)
{
std::cout << "this is probably not a PNG" << std::endl;
return;
}
if(last_type != type)
{
std::cout << std::endl;
std::cout << " " << type << ": ";
}
last_type = type;
std::cout << lodepng_chunk_length(chunk) << ", ";
next = lodepng_chunk_next_const(chunk);
if (next <= chunk) break; // integer overflow
chunk = next;
}
std::cout << std::endl;
}
unsigned getChunkInfo(std::vector<std::string>& names, std::vector<size_t>& sizes,
const std::vector<unsigned char>& png)
{
// Listing chunks is based on the original file, not the decoded png info.
const unsigned char *chunk, *begin, *end, *next;
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;
unsigned length = lodepng_chunk_length(chunk);
if(chunk + length + 12 > end) return 1;
names.push_back(type);
sizes.push_back(length);
next = lodepng_chunk_next_const(chunk);
if (next <= chunk) return 1; // integer overflow
chunk = next;
}
return 0;
}
unsigned getChunks(std::vector<std::string> names[3],
std::vector<std::vector<unsigned char> > chunks[3],
const std::vector<unsigned char>& 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<unsigned char>(chunk, next));
}
chunk = next;
}
return 0;
}
unsigned insertChunks(std::vector<unsigned char>& png,
const std::vector<std::vector<unsigned char> > chunks[3])
{
const unsigned char *chunk, *next, *begin, *end;
end = &png.back() + 1;
begin = chunk = &png.front() + 8;
ptrdiff_t l0 = 0; //location 0: IHDR-l0-PLTE (or IHDR-l0-l1-IDAT)
ptrdiff_t l1 = 0; //location 1: PLTE-l1-IDAT (or IHDR-l0-l1-IDAT)
ptrdiff_t 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 (next <= chunk) return 1; // integer overflow
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<unsigned char> 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;
}
/*
Show the filtertypes of each scanline in this PNG image.
*/
void displayFilterTypes(const std::vector<unsigned char>& buffer, bool ignore_checksums)
{
//Get color type and interlace type
lodepng::State state;
if(ignore_checksums)
{
state.decoder.ignore_crc = 1;
state.decoder.zlibsettings.ignore_adler32 = 1;
}
unsigned w, h;
unsigned error;
error = lodepng_inspect(&w, &h, &state, &buffer[0], buffer.size());
if(error)
{
std::cout << "inspect error " << error << ": " << lodepng_error_text(error) << std::endl;
return;
}
if(state.info_png.interlace_method == 1)
{
std::cout << "showing filtertypes for interlaced PNG not supported by this example" << std::endl;
return;
}
//Read literal data from all IDAT chunks
const unsigned char *chunk, *begin, *end, *next;
end = &buffer.back() + 1;
begin = chunk = &buffer.front() + 8;
std::vector<unsigned char> zdata;
while(chunk + 8 < end && chunk >= begin)
{
char type[5];
lodepng_chunk_type(type, chunk);
if(std::string(type).size() != 4)
{
std::cout << "this is probably not a PNG" << std::endl;
return;
}
if(std::string(type) == "IDAT")
{
const unsigned char* cdata = lodepng_chunk_data_const(chunk);
unsigned clength = lodepng_chunk_length(chunk);
if(chunk + clength + 12 > end || clength > buffer.size() || chunk + clength + 12 < begin) {
std::cout << "invalid chunk length" << std::endl;
return;
}
for(unsigned i = 0; i < clength; i++)
{
zdata.push_back(cdata[i]);
}
}
next = lodepng_chunk_next_const(chunk);
if (next <= chunk) break; // integer overflow
chunk = next;
}
//Decompress all IDAT data
std::vector<unsigned char> data;
error = lodepng::decompress(data, &zdata[0], zdata.size());
if(error)
{
std::cout << "decompress error " << error << ": " << lodepng_error_text(error) << std::endl;
return;
}
//A line is 1 filter byte + all pixels
size_t linebytes = 1 + lodepng_get_raw_size(w, 1, &state.info_png.color);
if(linebytes == 0)
{
std::cout << "error: linebytes is 0" << std::endl;
return;
}
std::cout << "Filter types: ";
for(size_t i = 0; i < data.size(); i += linebytes)
{
std::cout << (int)(data[i]) << " ";
}
std::cout << std::endl;
}
unsigned getFilterTypesInterlaced(std::vector<std::vector<unsigned char> >& filterTypes,
const std::vector<unsigned char>& 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, *next;
end = &png.back() + 1;
begin = chunk = &png.front() + 8;
std::vector<unsigned char> 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);
if(chunk + clength + 12 > end || clength > png.size() || chunk + clength + 12 < begin) {
// corrupt chunk length
return 1;
}
for(unsigned i = 0; i < clength; i++)
{
zdata.push_back(cdata[i]);
}
}
next = lodepng_chunk_next_const(chunk);
if (next <= chunk) return 1; // integer overflow
chunk = next;
}
//Decompress all IDAT data
std::vector<unsigned char> 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 */
}
