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File Content: `example5.cpp`

// example5.cpp

// This program is a simple example that prints a character's outline in the
// SVG format to stdout, demonstrating the usage of FT_Outline_Decompose().
//
// Developed by Static Jobs LLC and contributed to the FreeType project.
//
// Copyright (c) 2016-2018 Static Jobs LLC
//   IT and software engineering jobs in the US, Canada and the UK
//   https://www.staticjobs.com
//
// License: MIT (see below)
//
// The source code was reformatted by Werner Lemberg, also including a few
// minor code changes and comments for didactic purposes.
//
// On a Unix box like GNU/Linux or OS X, compile with
//
//    g++ -o example5 example5.cpp `pkg-config freetype2 --cflags --libs`
//
// or
//
//    g++ -o example5 example5.cpp `freetype-config --cflags --libs`
//
// on the command line.
//
// On other platforms that don't have the `freetype-config' shell script or
// the `pkg-config' tool, you have to pass the necessary compiler flags
// manually.


// Permission is hereby granted, free of charge, to any person obtaining a
// copy of this software and associated documentation files (the
// "Software"), to deal in the Software without restriction, including
// without limitation the rights to use, copy, modify, merge, publish,
// distribute, sublicense, and/or sell copies of the Software, and to permit
// persons to whom the Software is furnished to do so, subject to the
// following conditions:
//
// The above copyright notice and this permission notice shall be included
// in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
// IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
// CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT
// OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR
// THE USE OR OTHER DEALINGS IN THE SOFTWARE.


#include <iostream>
#include <sstream>
#include <stdexcept>
#include <cstring>
#include <cctype>

#include <ft2build.h>
#include FT_FREETYPE_H
#include FT_OUTLINE_H
#include FT_BBOX_H


using namespace std;


// A minimal wrapper for RAII (`resource acquisition is initialization').
class FreeTypeLibrary
{
public:
  FreeTypeLibrary();
  ~FreeTypeLibrary();

  operator FT_Library() const;

private:
  FreeTypeLibrary(const FreeTypeLibrary &);
  FreeTypeLibrary &operator =(const FreeTypeLibrary &);

private:
  FT_Library m_ftLibrary;
};


inline
FreeTypeLibrary::FreeTypeLibrary()
{
  FT_Error error = FT_Init_FreeType(&m_ftLibrary);

  if (error)
    throw runtime_error("Couldn't initialize the library:"
                        " FT_Init_FreeType() failed");
}


inline
FreeTypeLibrary::~FreeTypeLibrary()
{
  FT_Done_FreeType(m_ftLibrary);
}


inline
FreeTypeLibrary::operator FT_Library() const
{
  return m_ftLibrary;
}


// Another minimal wrapper for RAII.
class FreeTypeFace
{
public:
  FreeTypeFace(const FreeTypeLibrary &library,
               const char *filename);
  ~FreeTypeFace();

  operator FT_Face() const;

private:
  FreeTypeFace(const FreeTypeFace &);
  FreeTypeFace &operator =(const FreeTypeFace &);

private:
  FT_Face m_ftFace;
};


inline
FreeTypeFace::FreeTypeFace(const FreeTypeLibrary &library,
                           const char *filename)
{
  // For simplicity, always use the first face index.
  FT_Error error = FT_New_Face(library, filename, 0, &m_ftFace);

  if (error)
    throw runtime_error("Couldn't load the font file:"
                        " FT_New_Face() failed");
}


inline
FreeTypeFace::~FreeTypeFace()
{
  FT_Done_Face(m_ftFace);
}


inline
FreeTypeFace::operator FT_Face() const
{
  return m_ftFace;
}


class OutlinePrinter
{
public:
  OutlinePrinter(const char *filename);
  int Run(const char *symbol);

private:
  OutlinePrinter(const OutlinePrinter &);
  OutlinePrinter &operator =(const OutlinePrinter &);

private:
  void LoadGlyph(const char *symbol) const;
  bool OutlineExists() const;
  void FlipOutline() const;
  void ExtractOutline();
  void ComputeViewBox();
  void PrintSVG() const;

  static int MoveToFunction(const FT_Vector *to,
                            void *user);
  static int LineToFunction(const FT_Vector *to,
                            void *user);
  static int ConicToFunction(const FT_Vector *control,
                             const FT_Vector *to,
                             void *user);
  static int CubicToFunction(const FT_Vector *controlOne,
                             const FT_Vector *controlTwo,
                             const FT_Vector *to,
                             void *user);

private:
  // These two lines initialize the library and the face;
  // the order is important!
  FreeTypeLibrary m_library;
  FreeTypeFace m_face;

  ostringstream m_path;

  // These four variables are for the `viewBox' attribute.
  FT_Pos m_xMin;
  FT_Pos m_yMin;
  FT_Pos m_width;
  FT_Pos m_height;
};


inline
OutlinePrinter::OutlinePrinter(const char *filename)
: m_face(m_library, filename),
  m_xMin(0),
  m_yMin(0),
  m_width(0),
  m_height(0)
{
  // Empty body.
}


int
OutlinePrinter::Run(const char *symbol)
{
  LoadGlyph(symbol);

  // Check whether outline exists.
  bool outlineExists = OutlineExists();

  if (!outlineExists) // Outline doesn't exist.
    throw runtime_error("Outline check failed.\n"
                        "Please, inspect your font file or try another one,"
                        " for example LiberationSerif-Bold.ttf");

  FlipOutline();

  ExtractOutline();

  ComputeViewBox();

  PrintSVG();

  return 0;
}


void
OutlinePrinter::LoadGlyph(const char *symbol) const
{
  FT_ULong code = symbol[0];

  // For simplicity, use the charmap FreeType provides by default;
  // in most cases this means Unicode.
  FT_UInt index = FT_Get_Char_Index(m_face, code);

  FT_Error error = FT_Load_Glyph(m_face,
                                 index,
                                 FT_LOAD_NO_SCALE | FT_LOAD_NO_BITMAP);

  if (error)
    throw runtime_error("Couldn't load the glyph: FT_Load_Glyph() failed");
}


// While working on this example, we found fonts with no outlines for
// printable characters such as `A', i.e., `outline.n_contours' and
// `outline.n_points' were zero.  FT_Outline_Check() returned `true'.
// FT_Outline_Decompose() also returned `true' without walking the outline.
// That is, we had no way of knowing whether the outline existed and could
// be (or was) decomposed.  Therefore, we implemented this workaround to
// check whether the outline does exist and can be decomposed.
bool
OutlinePrinter::OutlineExists() const
{
  FT_Face face = m_face;
  FT_GlyphSlot slot = face->glyph;
  FT_Outline &outline = slot->outline;

  if (slot->format != FT_GLYPH_FORMAT_OUTLINE)
    return false; // Should never happen.  Just an extra check.

  if (outline.n_contours <= 0 || outline.n_points <= 0)
    return false; // Can happen for some font files.

  FT_Error error = FT_Outline_Check(&outline);

  return error == 0;
}


// This function flips outline around x-axis. We need it because
// FreeType and SVG use opposite vertical directions.
void
OutlinePrinter::FlipOutline() const
{
  const FT_Fixed multiplier = 65536L;

  FT_Matrix matrix;

  matrix.xx = 1L * multiplier;
  matrix.xy = 0L * multiplier;
  matrix.yx = 0L * multiplier;
  matrix.yy = -1L * multiplier;

  FT_Face face = m_face;
  FT_GlyphSlot slot = face->glyph;
  FT_Outline &outline = slot->outline;

  FT_Outline_Transform(&outline, &matrix);
}


void
OutlinePrinter::ExtractOutline()
{
  m_path << "  <path d='\n";

  FT_Outline_Funcs callbacks;

  callbacks.move_to = MoveToFunction;
  callbacks.line_to = LineToFunction;
  callbacks.conic_to = ConicToFunction;
  callbacks.cubic_to = CubicToFunction;

  callbacks.shift = 0;
  callbacks.delta = 0;

  FT_Face face = m_face;
  FT_GlyphSlot slot = face->glyph;
  FT_Outline &outline = slot->outline;

  FT_Error error = FT_Outline_Decompose(&outline, &callbacks, this);

  if (error)
    throw runtime_error("Couldn't extract the outline:"
                        " FT_Outline_Decompose() failed");

  m_path << "          '\n"
            "        fill='red'/>\n";
}


void
OutlinePrinter::ComputeViewBox()
{
  FT_Face face = m_face;
  FT_GlyphSlot slot = face->glyph;
  FT_Outline &outline = slot->outline;

  FT_BBox boundingBox;

  FT_Outline_Get_BBox(&outline, &boundingBox);

  FT_Pos xMin = boundingBox.xMin;
  FT_Pos yMin = boundingBox.yMin;
  FT_Pos xMax = boundingBox.xMax;
  FT_Pos yMax = boundingBox.yMax;

  m_xMin = xMin;
  m_yMin = yMin;
  m_width = xMax - xMin;
  m_height = yMax - yMin;
}


void
OutlinePrinter::PrintSVG() const
{
  cout << "<svg xmlns='http://www.w3.org/2000/svg'\n"
          "     xmlns:xlink='http://www.w3.org/1999/xlink'\n"
          "     viewBox='"
       << m_xMin << ' ' << m_yMin << ' ' << m_width << ' ' << m_height
       << "'>\n"
       << m_path.str()
       << "</svg>"
       << endl;
}


int
OutlinePrinter::MoveToFunction(const FT_Vector *to,
                               void *user)
{
  OutlinePrinter *self = static_cast<OutlinePrinter *>(user);

  FT_Pos x = to->x;
  FT_Pos y = to->y;

  self->m_path << "           "
                  "M " << x << ' ' << y << '\n';

  return 0;
}


int
OutlinePrinter::LineToFunction(const FT_Vector *to,
                               void *user)
{
  OutlinePrinter *self = static_cast<OutlinePrinter *>(user);

  FT_Pos x = to->x;
  FT_Pos y = to->y;

  self->m_path << "           "
                  "L " << x << ' ' << y << '\n';

  return 0;
}


int
OutlinePrinter::ConicToFunction(const FT_Vector *control,
                                const FT_Vector *to,
                                void *user)
{
  OutlinePrinter *self = static_cast<OutlinePrinter *>(user);

  FT_Pos controlX = control->x;
  FT_Pos controlY = control->y;

  FT_Pos x = to->x;
  FT_Pos y = to->y;

  self->m_path << "           "
                  "Q " << controlX << ' ' << controlY << ", "
                       << x << ' ' << y << '\n';

  return 0;
}


int
OutlinePrinter::CubicToFunction(const FT_Vector *controlOne,
                                const FT_Vector *controlTwo,
                                const FT_Vector *to,
                                void *user)
{
  OutlinePrinter *self = static_cast<OutlinePrinter *>(user);

  FT_Pos controlOneX = controlOne->x;
  FT_Pos controlOneY = controlOne->y;

  FT_Pos controlTwoX = controlTwo->x;
  FT_Pos controlTwoY = controlTwo->y;

  FT_Pos x = to->x;
  FT_Pos y = to->y;

  self->m_path << "           "
                  "C " << controlOneX << ' ' << controlOneY << ", "
                       << controlTwoX << ' ' << controlTwoY << ", "
                       << x << ' ' << y << '\n';

  return 0;
}


int
main(int argc,
     char **argv)
{
  if (argc != 3)
  {
    const char *program = argv[0];

    cerr << "This program prints a single character's outline"
            " in the SVG format to stdout.\n"
            "Usage: " << program << " font symbol\n"
            "Example: " << program << " LiberationSerif-Bold.ttf A" << endl;

    return 1;
  }

  const char *symbol = argv[2];

  // For simplicity, only accept single-byte characters like `A'.
  if (strlen(symbol) != 1 || isspace(*symbol))
  {
    cerr << "Error: '" << symbol
         << "' is not a single printable character" << endl;

    return 2;
  }

  int status;

  try
  {
    const char *filename = argv[1];

    OutlinePrinter printer(filename);

    status = printer.Run(symbol);
  }
  catch (const exception &e)
  {
    cerr << "Error: " << e.what() << endl;

    status = 3;
  }

  return status;
}

// EOF
Name	Size	Permission
example1.c	3934 bytes	0644
example2.cpp	10960 bytes	0644
example3.cpp	3754 bytes	0644
example4.cpp	6021 bytes	0644
example4.pro	249 bytes	0644
example5.cpp	11755 bytes	0644
example5.svg	1845 bytes	0644
index.html	5918 bytes	0644
metrics.png	2216 bytes	0644
metrics2.png	1853 bytes	0644
step1.html	45419 bytes	0644
step2.html	64321 bytes	0644
step3.html	5534 bytes	0644
File Content: example5.cpp

File Content: `example5.cpp`
