ale-sys 0.1.2

/* *****************************************************************************
 * A.L.E (Arcade Learning Environment)
 * Copyright (c) 2009-2013 by Yavar Naddaf, Joel Veness, Marc G. Bellemare and
 *   the Reinforcement Learning and Artificial Intelligence Laboratory
 * Released under the GNU General Public License; see License.txt for details.
 *
 * Based on: Stella  --  "An Atari 2600 VCS Emulator"
 * Copyright (c) 1995-2007 by Bradford W. Mott and the Stella team
 *
 * *****************************************************************************
 *  ScreenExporter.hpp
 *
 *  A class for exporting Atari 2600 frames as PNGs.
 *
 **************************************************************************** */

#include "ScreenExporter.hpp"

#include <zlib.h>
#include <sstream>
#include <fstream>

#include "Log.hpp"

namespace ale {

// MGB: These methods originally belonged to ExportScreen. Possibly these should be returned to
// their own class, rather than be static methods. They are here to avoid exposing the gritty
// details of PNG generation.
static void writePNGChunk(std::ofstream& out, const char* type, uInt8* data,
                          int size) {
  // Stuff the length/type into the buffer
  uInt8 temp[8];
  temp[0] = size >> 24;
  temp[1] = size >> 16;
  temp[2] = size >> 8;
  temp[3] = size;
  temp[4] = type[0];
  temp[5] = type[1];
  temp[6] = type[2];
  temp[7] = type[3];

  // Write the header
  out.write((const char*)temp, 8);

  // Append the actual data
  uInt32 crc = crc32(0, temp + 4, 4);
  if (size > 0) {
    out.write((const char*)data, size);
    crc = crc32(crc, data, size);
  }

  // Write the CRC
  temp[0] = crc >> 24;
  temp[1] = crc >> 16;
  temp[2] = crc >> 8;
  temp[3] = crc;
  out.write((const char*)temp, 4);
}

static void writePNGHeader(std::ofstream& out, const ALEScreen& screen,
                           bool doubleWidth = true) {
  int width = doubleWidth ? screen.width() * 2 : screen.width();
  int height = screen.height();
  // PNG file header
  uInt8 header[8] = {137, 80, 78, 71, 13, 10, 26, 10};
  out.write((const char*)header, sizeof(header));

  // PNG IHDR
  uInt8 ihdr[13];
  ihdr[0] = (width >> 24) & 0xFF; // width
  ihdr[1] = (width >> 16) & 0xFF;
  ihdr[2] = (width >> 8) & 0xFF;
  ihdr[3] = (width >> 0) & 0xFF;
  ihdr[4] = (height >> 24) & 0xFF; // height
  ihdr[5] = (height >> 16) & 0xFF;
  ihdr[6] = (height >> 8) & 0xFF;
  ihdr[7] = (height >> 0) & 0xFF;
  ihdr[8] = 8;  // 8 bits per sample (24 bits per pixel)
  ihdr[9] = 2;  // PNG_COLOR_TYPE_RGB
  ihdr[10] = 0; // PNG_COMPRESSION_TYPE_DEFAULT
  ihdr[11] = 0; // PNG_FILTER_TYPE_DEFAULT
  ihdr[12] = 0; // PNG_INTERLACE_NONE
  writePNGChunk(out, "IHDR", ihdr, sizeof(ihdr));
}

static void writePNGData(std::ofstream& out, const ALEScreen& screen,
                         const ColourPalette& palette,
                         bool doubleWidth = true) {
  int dataWidth = screen.width();
  int width = doubleWidth ? dataWidth * 2 : dataWidth;
  int height = screen.height();

  // If so desired, double the width

  // Fill the buffer with scanline data
  int rowbytes = width * 3;

  std::vector<uInt8> buffer((rowbytes + 1) * height, 0);
  uInt8* buf_ptr = &buffer[0];

  for (int i = 0; i < height; i++) {
    *buf_ptr++ = 0; // first byte of row is filter type
    for (int j = 0; j < dataWidth; j++) {
      int r, g, b;

      palette.getRGB(screen.getArray()[i * dataWidth + j], r, g, b);
      // Double the pixel width, if so desired
      int jj = doubleWidth ? 2 * j : j;

      buf_ptr[jj * 3 + 0] = r;
      buf_ptr[jj * 3 + 1] = g;
      buf_ptr[jj * 3 + 2] = b;

      if (doubleWidth) {
        jj = jj + 1;

        buf_ptr[jj * 3 + 0] = r;
        buf_ptr[jj * 3 + 1] = g;
        buf_ptr[jj * 3 + 2] = b;
      }
    }
    buf_ptr += rowbytes; // add pitch
  }

  // Compress the data with zlib
  uLongf compmemsize = (uLongf)((height * (width + 1) * 3 + 1) + 12);
  std::vector<uInt8> compmem(compmemsize, 0);

  if ((compress(&compmem[0], &compmemsize, &buffer[0],
                height * (width * 3 + 1)) != Z_OK)) {
    // @todo -- throw a proper exception
    ale::Logger::Error << "Error: Couldn't compress PNG" << std::endl;
    return;
  }

  // Write the compressed framebuffer data
  writePNGChunk(out, "IDAT", &compmem[0], compmemsize);
}

static void writePNGEnd(std::ofstream& out) {
  // Finish up
  writePNGChunk(out, "IEND", 0, 0);
}

ScreenExporter::ScreenExporter(ColourPalette& palette)
    : m_palette(palette), m_frame_number(0), m_frame_field_width(6) {}

ScreenExporter::ScreenExporter(ColourPalette& palette, const std::string& path)
    : m_palette(palette), m_frame_number(0), m_frame_field_width(6),
      m_path(path) {}

void ScreenExporter::save(const ALEScreen& screen,
                          const std::string& filename) const {
  // Open file for writing
  std::ofstream out(filename.c_str(), std::ios_base::binary);
  if (!out.good()) {
    // @todo exception
    ale::Logger::Error << "Could not open " << filename << " for writing"
                       << std::endl;
    return;
  }

  // Now write the PNG proper
  writePNGHeader(out, screen, true);
  writePNGData(out, screen, m_palette, true);
  writePNGEnd(out);

  out.close();
}

void ScreenExporter::saveNext(const ALEScreen& screen) {
  // Must have specified a directory.
  assert(m_path.size() > 0);

  // MGB: It would be nice here to automagically create paths, but the only way I know of
  // doing this cleanly is via boost, which we don't include.

  // Construct the filename from basepath & current frame number
  std::ostringstream oss;
  oss << m_path << "/" << std::setw(m_frame_field_width) << std::setfill('0')
      << m_frame_number << ".png";

  // Save the png
  save(screen, oss.str());

  m_frame_number++;
}

}  // namespace ale