path: root/example_png_info.cpp

/*
LodePNG Examples

Copyright (c) 2005-2012 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.
*/

//g++ lodepng.cpp example_png_info.cpp -ansi -pedantic -Wall -Wextra -lSDL -O3

/*
This sample shows a lot of information in the console about a PNG file,
including color type, text chunks, the names of all chunks in the image,
etc...
*/


#include "lodepng.h"
#include <iostream>

/*
Display general info about the PNG.
*/
void displayPNGInfo(const LodePNGInfo& info)
{
  const LodePNGColorMode& color = info.color;

  std::cout << "Compression method: " << info.compression_method << std::endl;
  std::cout << "Filter method: " << info.filter_method << std::endl;
  std::cout << "Interlace method: " << info.interlace_method << std::endl;
  std::cout << "Color type: " << color.colortype << std::endl;
  std::cout << "Bit depth: " << color.bitdepth << std::endl;
  std::cout << "Bits per pixel: " << lodepng_get_bpp(&color) << std::endl;
  std::cout << "Channels per pixel: " << lodepng_get_channels(&color) << std::endl;
  std::cout << "Is greyscale type: " << lodepng_is_greyscale_type(&color) << std::endl;
  std::cout << "Can have alpha: " << lodepng_can_have_alpha(&color) << std::endl;
  std::cout << "Palette size: " << color.palettesize << std::endl;
  std::cout << "Has color key: " << color.key_defined << std::endl;
  if(color.key_defined)
  {
    std::cout << "Color key r: " << color.key_r << std::endl;
    std::cout << "Color key g: " << color.key_g << std::endl;
    std::cout << "Color key b: " << color.key_b << std::endl;
  }
  std::cout << "Texts: " << info.text_num << std::endl;
  for(size_t i = 0; i < info.text_num; i++)
  {
    std::cout << "Text: " << info.text_keys[i] << ": " << info.text_strings[i] << std::endl << std::endl;
  }
  std::cout << "International texts: " << info.itext_num << std::endl;
  for(size_t i = 0; i < info.itext_num; i++)
  {
    std::cout << "Text: "
              << info.itext_keys[i] << ", "
              << info.itext_langtags[i] << ", "
              << info.itext_transkeys[i] << ": "
              << info.itext_strings[i] << std::endl << std::endl;
  }
  std::cout << "Time defined: " << info.time_defined << std::endl;
  if(info.time_defined)
  {
    const LodePNGTime& time = info.time;
    std::cout << "year: " << time.year << std::endl;
    std::cout << "month: " << time.month << std::endl;
    std::cout << "day: " << time.day << std::endl;
    std::cout << "hour: " << time.hour << std::endl;
    std::cout << "minute: " << time.minute << std::endl;
    std::cout << "second: " << time.second << std::endl;
  }
  std::cout << "Physics defined: " << info.phys_defined << std::endl;
  if(info.phys_defined)
  {
    std::cout << "physics X: " << info.phys_x << std::endl;
    std::cout << "physics Y: " << info.phys_y << std::endl;
    std::cout << "physics unit: " << info.phys_unit << std::endl;
  }
}


/*
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;
}


/*
Show ASCII art preview of the image
*/
void displayAsciiArt(const std::vector<unsigned char>& image, unsigned w, unsigned h)
{
  if(w > 0 && h > 0)
  {
    std::cout << std::endl << "ASCII Art Preview: " << std::endl;
    unsigned w2 = 48;
    if(w < w2) w2 = w;
    unsigned h2 = h * w2 / w;
    h2 = (h2 * 2) / 3; //compensate for non-square characters in terminal
    if(h2 > (w2 * 2)) h2 = w2 * 2; //avoid too large output

    std::cout << '+';
    for(unsigned x = 0; x < w2; x++) std::cout << '-';
    std::cout << '+' << std::endl;
    for(unsigned y = 0; y < h2; y++)
    {
      std::cout << "|";
      for(unsigned x = 0; x < w2; x++)
      {
        unsigned x2 = x * w / w2;
        unsigned y2 = y * h / h2;
        int r = image[y2 * w * 4 + x2 * 4 + 0];
        int g = image[y2 * w * 4 + x2 * 4 + 1];
        int b = image[y2 * w * 4 + x2 * 4 + 2];
        int a = image[y2 * w * 4 + x2 * 4 + 3];
        int lightness = ((r + g + b) / 3) * a / 255;
        int min = (r < g && r < b) ? r : (g < b ? g : b);
        int max = (r > g && r > b) ? r : (g > b ? g : b);
        int saturation = max - min;
        int letter = 'i'; //i for grey, or r,y,g,c,b,m for colors
        if(saturation > 32)
        {
          int h = lightness >= (min + max) / 2;
          if(h) letter = (min == r ? 'c' : (min == g ? 'm' : 'y'));
          else letter = (max == r ? 'r' : (max == g ? 'g' : 'b'));
        }
        int symbol = ' ';
        if(lightness > 224) symbol = '@';
        else if(lightness > 128) symbol = letter - 32;
        else if(lightness > 32) symbol = letter;
        else if(lightness > 16) symbol = '.';
        std::cout << (char)symbol;
      }
      std::cout << "|";
      std::cout << std::endl;
    }
    std::cout << '+';
    for(unsigned x = 0; x < w2; x++) std::cout << '-';
    std::cout << '+' << std::endl;
  }
}


/*
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;

}


/*
Main
*/
int main(int argc, char *argv[]) /*list the chunks*/
{
  bool ignore_checksums = false;
  std::string filename = "";
  for (int i = 1; i < argc; i++)
  {
    if(std::string(argv[i]) == "--ignore_checksums") ignore_checksums = true;
    else filename = argv[i];
  }
  if(filename == "")
  {
    std::cout << "Please provide a filename to preview" << std::endl;
    return 0;
  }

  std::vector<unsigned char> buffer;
  std::vector<unsigned char> image;
  unsigned w, h;

  lodepng::load_file(buffer, filename); //load the image file with given filename

  lodepng::State state;
  if(ignore_checksums)
  {
    state.decoder.ignore_crc = 1;
    state.decoder.zlibsettings.ignore_adler32 = 1;
  }

  unsigned error = lodepng::decode(image, w, h, state, buffer);

  if(error)
  {
    std::cout << "decoder error " << error << ": " << lodepng_error_text(error) << std::endl;
    return 0;
  }

  std::cout << "Filesize: " << buffer.size() << " (" << buffer.size() / 1024 << "K)" << std::endl;
  std::cout << "Width: " << w << std::endl;
  std::cout << "Height: " << h << std::endl;
  std::cout << "Num pixels: " << w * h << std::endl;

  if(w > 0 && h > 0)
  {
    std::cout << "Top left pixel color:"
              << " r: " << (int)image[0]
              << " g: " << (int)image[1]
              << " b: " << (int)image[2]
              << " a: " << (int)image[3]
              << std::endl;
  }


  displayPNGInfo(state.info_png);
  std::cout << std::endl;
  displayChunkNames(buffer);
  std::cout << std::endl;
  displayFilterTypes(buffer, ignore_checksums);
  std::cout << std::endl;
  displayAsciiArt(image, w, h);
}