Initial commit

master
Fabien Freling 2014-06-18 08:47:10 +02:00
commit 4bf69e8204
5 changed files with 500 additions and 0 deletions

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.gitignore vendored Normal file
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.DS_Store
*.dSYM
*.swp
*.ppm

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Makefile Normal file
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CXX = clang++
CXXFLAGS = -std=c++11 -W -Wall -Werror -O3
BUILD_DIR=/tmp
all: rotation.cpp
$(CXX) $(CXXFLAGS) $< -o $(BUILD_DIR)/rotation
clean:
@rm -f *~ *.o .*.swp

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TODO.md Normal file
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img/luigi.jpg Normal file

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rotation.cpp Normal file
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#include <string>
#include <fstream>
#include <iostream>
#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)
{
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;
}
};
//
//
// Drawing
//
void draw_line(Image& img, unsigned int x1, unsigned int y1, unsigned int x2, unsigned int y2)
{
assert(x1 < x2);
double const slope = (double) (y2 - y1) / (double) (x2 - x1);
for (unsigned int i = x1; i <= x2; ++i)
{
unsigned int y = slope * (i - x1) + y1;
img.set_pixel(i, y, 255, 0, 0); // set line to red
}
}
void draw_line(Image& img, Point const& p1, Point const& p2)
{
draw_line(img, p1.x, p1.y, p2.x, p2.y);
}
Point rotate(Image const& img, Point const& src, double radian, double const ratio)
{
cout << "rotate (" << src.x << ", " << src.y << ") x " << radian << endl;
double x = src.x - (img.width / 2.0f);
x *= ratio;
// double y = - src.y + (src.height / 2.0f);
// y *= ratio;
double const angle_value = acos(x) + radian;
double const cos_x = cos(angle_value);
double const sin_x = sin(angle_value);
unsigned int const new_x = ceil(cos_x / ratio);
unsigned int const new_y = ceil(sin_x / ratio);
cout << " = (" << new_x << ", " << new_y << ")" << endl;
return Point(new_x, new_y);
}
//
//
// Trigonometry
//
double convert_radian(Image const& img, Point const& p, double const ratio)
{
cout << "X: " << p.x << " - " << img.width / 2.0f << endl;
cout << "Y: " << - (int) p.y << " + " << img.height / 2.0f << endl;
double const centered_x = p.x - (img.width / 2.0f);
double const centered_y = (- (int) p.y) + (img.height / 2.0f);
cout << "centered point (" << centered_x << ", " << centered_y << ")" << endl;
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;
}
APoint convert_abs_coord(double const angle, double const ratio)
{
cout << "Angle: " << angle << endl;
cout << "cos: " << cos(angle) << endl;
cout << "sin: " << sin(angle) << endl;
APoint tmp((int) ceil(cos(angle) / ratio), (int) ceil(sin(angle) / ratio));
cout << "point: " << tmp << endl;
return APoint((int) ceil(cos(angle) / ratio), (int) ceil(sin(angle) / ratio));
}
Point convert_img_coord(Image const& img, APoint const& p)
{
cout << "image: " << img.width << " x " << img.height << endl;
cout << "p: " << p << endl;
cout << "h / 2: " << img.height / 2.0f << endl;
return Point(p.x + img.width / 2.0f, - p.y + img.height / 2.0f);
}
double compute_ratio(Image const& img)
{
cout << "Compute ratio" << endl;
unsigned int const nb_points = img.width * img.height;
cout << " " << nb_points << " points" << endl;
double const square_side = sqrt(nb_points) - 1;
cout << " square side: " << square_side << endl;
double const half_side = square_side / 2;
cout << " half side: " << half_side << endl;
unsigned int const trigo_length = (unsigned int) ceil(half_side * sqrt(2));
cout << " trigo length: " << trigo_length << endl;
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);
int min_w = 0;
int max_w = 0;
int min_h = 0;
int max_h = 0;
cout << "Image dimensions: " << src.width << " x " << src.height << endl;
Point p(0, 0);
double angle = convert_radian(src, p, ratio);
APoint 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);
APoint 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);
APoint 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);
APoint 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 = max_w - min_w + 1;
height = max_h - min_h + 1;
}
bool check_trigo()
{
Image square(500, 500);
double const ratio = compute_ratio(square);
// 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 (abs(angle - (3 * M_PI / 4)) > sigma)
{
cout << "Invalid angle value: " << angle << " != " << 3 * M_PI / 4 << endl;
return false;
}
// Check that we can reverse the origin point.
APoint 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 (!fequal(w, square.width * sqrt(2), sigma)
// || !fequal(h, square.height * sqrt(2), sigma))
// {
// 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);
APoint const a_p45 = convert_abs_coord(angle + rotation, ratio);
Point const p45 = convert_img_coord(rotated, a_p45);
if (abs((float) (-1) - p45.x) > sigma)
{
cerr << "Rotation origin by 45 degrees:" << endl;
cerr << "Invalid x value: " << p45.x << " != " << -1 << endl;
cerr << "Absolute point: (" << a_p45.x << ", " << a_p45.y << ")" << endl;
return false;
}
if (abs(0.0 - p45.y) > sigma)
{
cerr << "Rotation origin by 45 degrees:" << endl;
cerr << "Invalid y value: " << p45.y << " != " << 0 << endl;
return false;
}
return true;
}
//
//
// Rotation
//
Image rotate(Image const& src, double angle)
{
unsigned int const nb_points = src.width * src.height;
double const square_side = sqrt(nb_points);
double const half_side = square_side / 2;
unsigned int const trigo_length = (unsigned int) ceil(half_side * sqrt(2));
double const ratio = 1.0f / trigo_length;
// top left
double const cos_value = - (src.width / 2.0f) * ratio;
// double const sin_value = (src.height / 2.0f) * ratio;
double const angle_value = acos(cos_value);
cout << "top left angle: " << angle_value << endl;
double const radian = (angle / 360.0f) * (2 * M_PI);
// FIXME
Image rot(trigo_length, trigo_length);
Point tl = rotate(src, Point(0, 0), radian, ratio);
Point tr = rotate(src, Point(src.width - 1, 0), radian, ratio);
draw_line(rot, tl, tr);
// draw_line(rot, 0, 0, rot.width - 1, 0);
// draw_line(rot, 0, rot.height - 1, rot.width - 1, rot.height - 1);
// draw_line(rot, 0, 0, rot.width - 1, rot.height - 1);
// rot.set_pixel(rot.width - 1, rot.height - 1, 0, 255, 0);
// draw_line(rot, 0, 0, 0, rot.height - 1);
// draw_line(rot, rot.width - 1, 0, rot.width - 1, rot.height - 1);
return rot;
}
//
//
// Main
//
int main()
{
if (!check_trigo())
return 1;
return 0;
Image img("img/luigi.ppm");
Image rotated = rotate(img, 30);
rotated.save("rotated.ppm");
return 0;
}