rotate-me-fast/rotation.cpp

#include <string>
#include <fstream>
#include <iostream>
#include <sstream>
#include <cmath>
#include <cassert>
#include <cstring>

using namespace std;


template <typename T>
struct TPoint {
  T x;
  T y;

  TPoint(T a, T b)
  : x(a)
  , y(b)
  {}
};
typedef TPoint<unsigned int> Point;
typedef TPoint<int> APoint; // absolute point, can be negative
typedef TPoint<double> DPoint; // absolute point, can be negative
template<typename Elem, typename Traits, typename T>
std::basic_ostream<Elem, Traits>& operator << (std::basic_ostream<Elem, Traits>& o, TPoint<T> const& p)
{
  o << "(" << p.x << ", " << p.y << ")";
  return o;
}

struct Image {
  unsigned int width;
  unsigned int height;
  uint8_t* r_chan;
  uint8_t* g_chan;
  uint8_t* b_chan;

  Image()
  : width(0)
  , height(0)
  , r_chan(NULL)
  , g_chan(NULL)
  , b_chan(NULL)
  {}

  Image(unsigned int w, unsigned int h)
  {
    this->width = w;
    this->height = h;
    r_chan = new uint8_t[width * height];
    memset(r_chan, 0, width * height * sizeof (uint8_t));
    g_chan = new uint8_t[width * height];
    memset(g_chan, 0, width * height * sizeof (uint8_t));
    b_chan = new uint8_t[width * height];
    memset(b_chan, 0, width * height * sizeof (uint8_t));
  }

  Image(string const& path)
  : Image()
  {
    ifstream is(path);
    if (!is.is_open())
    {
      cerr << "Cannot open file '" << path << "'" << endl;
      abort();
    }

    if (!this->read_header(is))
    {
      cerr << "Invalid header." << endl;
      abort();
    }

    if (!this->read_body(is))
    {
      delete r_chan;
      r_chan = nullptr;
      delete g_chan;
      r_chan = nullptr;
      delete b_chan;
      r_chan = nullptr;

      cerr << "Invalid header." << endl;
      abort();
    }
  }

  bool save(string const& path)
  {
    ofstream os(path);
    if (!os.is_open())
    {
      cerr << "Cannot open file '" << path << "'" << endl;
      return false;
    }
    this->write_header(os);
    this->write_body(os);
    return true;
  }

  void set_pixel(unsigned int x, unsigned int y, uint8_t r, uint8_t g, uint8_t b)
  {
    if (x >= width || y >= height)
    {
        cerr << "Point (" << x << ", " << y << ") out of bounds" << endl;
        cerr << " Image dimensions: " << width << " x " << height << endl;
        assert(false);
    }
    int const index = y * width + x;
    r_chan[index] = r;
    g_chan[index] = g;
    b_chan[index] = b;
  }

  private:
    bool read_header(std::ifstream& istr)
    {
      // check magic
      if (istr.get() != 'P' )
      {
        return false;
      }

      char type = static_cast<char>(istr.get());
      if (type != '6')
      {
        return false;
      }

      if (istr.get() != '\n')
      {
        return false;
      }

      // skip comments
      while (istr.peek() == '#')
      {
        std::string line;
        std::getline(istr, line);
      }

      // get size
      istr >> width >> height;
      if (width == 0 || height == 0)
      {
        return false;
      }

      // get maxvalue
      if (istr.get() != '\n')
      {
        return false;
      }

      int max_value = -1;
      istr >> max_value;
      if (max_value > 255)
      {
        return false;
      }

      if (istr.get() != '\n')
      {
        return false;
      }

      cout << "width: " << width << endl;
      cout << "height: " << height << endl;

      return true;
    }

    bool write_header(std::ofstream& ostr)
    {
      ostr << "P6" << endl;
      ostr << width << " " << height << endl;
      ostr << "255" << endl;
      return true;
    }

    bool read_body(std::ifstream& istr)
    {
      r_chan = new uint8_t[width * height];
      g_chan = new uint8_t[width * height];
      b_chan = new uint8_t[width * height];

      for (unsigned int row = 0; row < height; ++row)
      {
        for (unsigned int col = 0; col < width; ++col)
        {
          int index = row * width + col;
          r_chan[index] = istr.get();
          g_chan[index] = istr.get();
          b_chan[index] = istr.get();
        }
      }

      return true;
    }

    bool write_body(std::ofstream& ostr)
    {
      for (unsigned int row = 0; row < height; ++row)
      {
        for (unsigned int col = 0; col < width; ++col)
        {
          int index = row * width + col;
          ostr << (char) r_chan[index];
          ostr << (char) g_chan[index];
          ostr << (char) b_chan[index];
        }
      }
      return true;
    }
};



//
//
// Trigonometry
//

DPoint convert_grid_coord(Image const& img, Point const& p)
{
  return DPoint(p.x - img.width / 2.0f + 0.5, p.y - img.height / 2.0f + 0.5);
}

double convert_radian(Image const& img, Point const& p, double const ratio)
{
  DPoint centered = convert_grid_coord(img, p);
  double const cos_value = centered.x * ratio;
  double const sin_value = - (centered.y * ratio);
  double angle = acos(cos_value);
  if (sin_value < 0)
    angle = 2 * M_PI - angle;

  return angle;
}

DPoint convert_abs_coord(double const angle, double const ratio)
{
  return DPoint(cos(angle) / ratio, - (sin(angle) / ratio));
}

Point convert_img_coord(Image const& img, DPoint const& p)
{
  int x = round(p.x + (img.width / 2.0f) - 0.5);
  int y = round(p.y + (img.height / 2.0f) - 0.5);
  Point p_mapped(x, y);
//  if (p_mapped.x >= img.width || p_mapped.y >= img.height)
//  {
//    cerr << "Point coord mapping" << endl;
//    cerr << " Input point:" << p << endl;
//    cerr << " Point " << p_mapped << " out of bounds" << endl;
//    cerr << " Image dimensions: " << img.width << " x " << img.height << endl;
//    assert(false);
//  }

  return p_mapped;
}

double compute_ratio(Image const& img)
{
  unsigned int const nb_points = img.width * img.height;
  double const square_side = sqrt(nb_points) - 1;
  double const half_side = square_side / 2;
  double const trigo_length = ceil(half_side * sqrt(2));
  return 1.0f / trigo_length;
}

inline
bool fequal(float a, float b, float sigma)
{
  return abs(a - b) < sigma;
}

void compute_output_size(Image const& src, double const rotation, unsigned int& width, unsigned int& height)
{
  double const ratio = compute_ratio(src);
  double min_w = 0;
  double max_w = 0;
  double min_h = 0;
  double max_h = 0;

  //cout << "Image dimensions: " << src.width << " x " << src.height << endl;
  Point p(0, 0);
  double angle = convert_radian(src, p, ratio);
  DPoint tl = convert_abs_coord(angle + rotation, ratio);
  min_w = min(min_w, tl.x);
  max_w = max(max_w, tl.x);
  min_h = min(min_h, tl.y);
  max_h = max(max_h, tl.y);
  //cout << "Rotated " << p << " (" << angle << ") = " << tl << "(" << angle + rotation << ")" << endl << endl;

  p = Point(src.width - 1, 0);
  angle = convert_radian(src, p, ratio);
  DPoint tr = convert_abs_coord(angle + rotation, ratio);
  min_w = min(min_w, tr.x);
  max_w = max(max_w, tr.x);
  min_h = min(min_h, tr.y);
  max_h = max(max_h, tr.y);
  //cout << "Rotated " << p << " (" << angle << ") = " << tr << "(" << angle + rotation << ")" << endl << endl;

  p = Point(0, src.height - 1);
  angle = convert_radian(src, p, ratio);
  DPoint bl = convert_abs_coord(angle + rotation, ratio);
  min_w = min(min_w, bl.x);
  max_w = max(max_w, bl.x);
  min_h = min(min_h, bl.y);
  max_h = max(max_h, bl.y);
  //cout << "Rotated " << p << " (" << angle << ") = " << bl << "(" << angle + rotation << ")" << endl << endl;

  p = Point(src.width - 1, src.height - 1);
  angle = convert_radian(src, p, ratio);
  DPoint br = convert_abs_coord(angle + rotation, ratio);
  min_w = min(min_w, br.x);
  max_w = max(max_w, br.x);
  min_h = min(min_h, br.y);
  max_h = max(max_h, br.y);
  //cout << "Rotated " << p << " (" << angle << ") = " << br << "(" << angle + rotation << ")" << endl << endl;

  width = (int) (max_w - min_w) + 1;
  height = (int) (max_h - min_h) + 1;
}


//
//
// Rotation
//

Point rotate(Image const& src, Point const& p, double const ratio, double const rotation, Image const& rotated)
{
  double angle = convert_radian(src, p, ratio);
  DPoint a_point = convert_abs_coord(angle + rotation, ratio);
  return convert_img_coord(rotated, a_point);
}

Image rotate(Image const& src, double angle)
{
  // FIXME
  Image rot(0, 0);
  cout << angle << src.width << endl; // to remove warnings
  return rot;
}



//
//
// Drawing
//

void draw_line(Image& img, unsigned int x1, unsigned int y1, unsigned int x2, unsigned int y2)
{
  if (x1 > x2)
  {
    swap(x1, x2);
    swap(y1, y2);
  }
  unsigned int const y_min = min(y1, y2);
  unsigned int const y_max = max(y1, y2);
  double const slope = ((double) y2 - y1) / ((double) x2 - x1);
  int y_inc = slope > 0 ? 1 : -1;

  unsigned int previous_y = y1;
  for (unsigned int i = x1; i <= x2; ++i)
  {
    unsigned int y = slope * (i - x1) + y1;
    y = min(y, y_max);
    y = max(y, y_min);
    for (unsigned int runner = previous_y; runner != y; runner+= y_inc)
      img.set_pixel(i, runner, 255, 0, 0); // set line to red
    previous_y = y;
  }
}

void draw_line(Image& img, Point const& p1, Point const& p2)
{
  draw_line(img, p1.x, p1.y, p2.x, p2.y);
}

void draw_outline(Image const& input, unsigned int degrees, string const& name)
{
  double const rotation = (degrees / 180.0f) * M_PI;
  unsigned int w = 0;
  unsigned int h = 0;
  compute_output_size(input, rotation, w, h);
  cout << "rotation(" << degrees << ") -> " << w << " x " << h << endl;
  Image rotated(w, h);

  double const ratio = compute_ratio(input);
  Point tl = rotate(input, Point(0, 0), ratio, rotation, rotated);
  Point tr = rotate(input, Point(input.width - 1, 0), ratio, rotation, rotated);
  Point bl = rotate(input, Point(0, input.height - 1), ratio, rotation, rotated);
  Point br = rotate(input, Point(input.width - 1, input.height - 1), ratio, rotation, rotated);
  cout << tl << " " << tr << " " << bl << " " << br << endl;

  draw_line(rotated, tl, tr);
  draw_line(rotated, tr, br);
  draw_line(rotated, br, bl);
  draw_line(rotated, bl, tl);

  stringstream ss;
  ss << "check_lines_" << name << "_" << degrees << ".ppm";
  rotated.save(ss.str());
}


//
//
// Check
//

bool check_points()
{
  Image five(5, 5);
  Point origin(0, 0);
  DPoint d1 = convert_grid_coord(five, origin);
  assert(d1.x == -2);
  assert(d1.y == -2);

  return true;
}

bool check_trigo()
{
  Image square(500, 500);
  double const ratio = compute_ratio(square);
  cout << "ratio: " << ratio << endl;

  // Check that the origin of a square image is at sqrt(2) / 2
  double const angle = convert_radian(square, Point(0, 0), ratio);

  double const sigma = 1.0e-2;
  if (!fequal(angle, 3 * M_PI / 4, sigma))
  {
    cout << __LINE__ << " | Invalid angle value: " << angle << " != " << 3 * M_PI / 4 << endl;
    return false;
  }

  // Check that we can reverse the origin point.
  DPoint const abs_reverse_point = convert_abs_coord(angle, ratio);
  cout << "reversed abs origin: " << abs_reverse_point << endl;
  Point const reverse_point = convert_img_coord(square, abs_reverse_point);
  cout << "reversed origin in square: " << reverse_point << endl;
  if (abs(0.0 - reverse_point.x) > sigma)
  {
    cerr << "Reverse origin:" << endl;
    cout << "Invalid x value: " << reverse_point.x << " != " << 0 << endl;
    return false;
  }
  if (abs(0.0 - reverse_point.y) > sigma)
  {
    cerr << "Reverse origin:" << endl;
    cout << "Invalid y value: " << reverse_point.y << " != " << 0 << endl;
    return false;
  }

  // Check that when rotating the origin by 45 degrees
  double const rotation = M_PI / 4; // 45 degrees
  unsigned int w = 0;
  unsigned int h = 0;
  compute_output_size(square, rotation, w, h);

  // failed check: is precision an issue?
  if (true)
  {
    if (!fequal(w, square.width * sqrt(2), sigma * square.width)
        || !fequal(h, square.height * sqrt(2), sigma * square.height))
    {
      cerr << "Invalid rotated image dimensions " << w << " x " << h << endl;
      cerr << " expected " << (int) ceil(square.width * sqrt(2)) << " x " << (int) ceil(square.height * sqrt(2)) << endl;
      return false;
    }


    Image rotated(w, h);

    DPoint const a_p45 = convert_abs_coord(angle + rotation, ratio);
    Point const p45 = convert_img_coord(rotated, a_p45);
    if (!fequal(0, p45.x, sigma))
    {
      cerr << __LINE__ << " > Rotation origin by 45 degrees:" << endl;
      cerr << " invalid x value: " << p45.x << " != " << 0 << endl;
      cerr << " absolute point: " << a_p45 << endl;
      cerr << " relative point: " << p45 << endl;
      return false;
    }
    if (!fequal(p45.y, h / 2.0f - 1, sigma))
    {
      cerr << __LINE__ << " > Rotation origin by 45 degrees:" << endl;
      cerr << "Invalid y value: " << p45.y << " != " << h / 2.0f - 1 << endl;
      cerr << " absolute point: " << a_p45 << endl;
      cerr << " relative point: " << p45 << endl;
      return false;
    }
  }

  return true;
}

void check_lines()
{
  Image const square(500, 500);
  draw_outline(square, 22, "square");
  draw_outline(square, 33, "square");
  draw_outline(square, 45, "square");
  draw_outline(square, 90, "square");

  Image const rect1(640, 480);
  draw_outline(rect1, 22, "rect1");
  draw_outline(rect1, 33, "rect1");
  draw_outline(rect1, 45, "rect1");
  draw_outline(rect1, 90, "rect1");
}



//
//
// Main
//

int main()
{
  check_points();

  if (!check_trigo())
    return 1;

  check_lines();

  return 0;

  Image img("img/luigi.ppm");

  Image rotated = rotate(img, 30);
  rotated.save("rotated.ppm");

  return 0;
}