rgb

#include <fstream>
// using std::ofstream, std::ifstream, std::streampos

void write(const char* fname, const SomeType& processedImage)
{
  std::ofstream file(fname);
  file.exceptions(std::ofstream::badbit);

  const unsigned short cols = image.columns(), rows = image.rows();
  file.write(reinterpret_cast<const char*>(&cols), sizeof(cols));

  for(int col = 0; col != cols; ++col) {
    for(int row = 0; row != rows; ++row) {
      const Magick::ColorRGB rgb = processedImage.pixelColor(col, row);
      const unsigned char bytes[] = {
    rgb.red() * 255, rgb.green() * 255, rgb.blue() * 255
      };
      file.write(reinterpret_cast<const char*>(bytes), sizeof(bytes));
    }
  }
}

void read(const char* fname, SomeType& imageOutput)
{
  std::ifstream file(fname);
  file.exceptions(std::ifstream::badbit | std::ifstream::failbit);

  unsigned short cols;
  file.read(reinterpret_cast<char*>(&cols), sizeof(cols));
  const std::streampos pos = file.tellg();
  file.seekg(0, std::ifstream::end);
  const std::streampos end = file.tellg();
  const unsigned short rows = (end - pos) / (cols * 3);
  file.seekg(pos, std::ifstream::beg);

  imageOutput.setCols(cols);
  imageOutput.setRows(rows);

  for(int col = 0; col != cols; ++col) {
    for(int row = 0; row != rows; ++row) {
      unsigned char bytes[3];
      file.read(reinterpret_cast<char*>(&bytes), sizeof(bytes));
      const Magick::ColorRGB rgb(bytes[0] / 255., bytes[1] / 255., bytes[2] / 255.);
      imageOutput.setPixelColor(col, row, rgb);
    }
  }
}