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<h1>
FreeType 2.0 Tutorial</h1></center>

<center>
<h3>
&copy; 2000 David Turner (<a href="mailto:david@freetype.org">david@freetype.org</a>)<br>
&copy; 2000 The FreeType Development Team
(<a href="http://www.freetype.org">www.freetype.org</a>)
</h3></center>

<center>
<table width=650><tr><td>

<p><br>
<hr WIDTH="100%">
<br>&nbsp;
<h2>Introduction:</h2>
<ul>
    This simple tutorial will teach you how to use the FreeType 2 library
    in your own applications.
</ul>

<p><hr><p>

<h3>1. Header files :</h3>
<ul>
  To include the main FreeType header file, simply use:<p>
  <ul><font color="blue"><tt>
      #include &lt;freetype/freetype.h&gt;<p>
  </tt></font></ul>
  in your application code. Note that other files are available in the
  FreeType include directory, most of them being included by
  <tt>"freetype.h"</tt>. They will be described later in this tutorial.
</ul>

<p><hr><p>

<h3>2. Initialise the library:</h3>
<ul>
  Simply create a variable of type <tt>FT_Library</tt> named, for example,
  <tt>library</tt>, and call the function <tt>FT_Init_FreeType</tt> as in:

  <font color="blue"><pre>
       #include &lt;freetype/freetype.h&gt;

       FT_Library  library;

       ....

       {
         ..
         error = FT_Init_FreeType( &library );
         if (error) { .. an error occured during library initialisation .. }
       }
  </pre></font>
  <p>
  This function is in charge of the following:<p>
  <ul>
      <li>Creating a new instance of the FreeType 2 library, and set
          the handle <tt>library</tt> to it.
          <p>

      <li>Load each font driver that FreeType knows about in the library.
          This means that by default, your new <tt>library</tt> object is
          able to handle TrueType and Type 1 fonts gracefully.
          <p>
  </ul>
  <p>
  As you can see, the function returns an error code, like most others in the
  FreeType API. An error code of 0 <em>always</em> means that the operation
  was succesful; otherwise, the value describes the error, and <tt>library</tt>
  is set to NULL.
</ul>

<p><hr><p>

<h3>3. Load a font face:</h3>
<ul>
  <h4>a. From a font file:</h4>
  <ul>
    Create a new <em>face</em> object by calling <tt>FT_New_Face</tt>. A
    <em>face</em> describes a given typeface and style. For example,
    "Times New Roman Regular" and "Times New Roman Italic" correspond to
    two different faces.
    <p>
    <font color="blue"><pre>

      FT_Library   library;   /* handle to library     */
      FT_Face      face;      /* handle to face object */

      error = FT_Init_FreeType( &library );
      if (error) { ..... }

      error = FT_New_Face( library,
                           "/usr/share/fonts/truetype/arial.ttf",
                           0,
                           &face );
      if (error == FT_Err_Unknown_File_Format)
      {
         .... the font file could be opened and read, but it appears
         .... that its font format is unsupported
      }
      else if (error)
      {
         .... another error code means that the font file could not
         .... be opened, read or simply that it is broken..
      }
    </pre></font>
    <p>
    As you certainly imagine, <tt>FT_New_Face</tt> opens a font file then
    tries to extract one face from it. Its parameters are :<p>
    <ul>
    <table cellpadding=5>
    <tr valign="top"><td><tt><b>library</b></tt>
        <td>handle to the FreeType library instance where the face object is
            created

    <tr valign="top"><td><tt><b>filepathname</b></tt>
        <td>the font file pathname (standard C string).

    <tr valign="top"><td><tt><b>face_index</b></tt>
        <td>Certain font formats allow several font faces to be embedded in
            a single file.<br>
            This index tells which face you want to load. An
            error will be returned if its value is too large.<br>
            Index 0 always work though.

    <tr><td><tt><b>face</b></tt>
        <td>A <em>pointer</em> to the handle that will be set to
            describe the new face object.<br>
            It is set to NULL in case of error.
    </table>
    </ul>
    <p>
    To known how many faces a given font file contains, simply load its
    first face (use <tt>face_index</tt>=0), then see the value of
    <tt>face->num_faces</tt> which indicates how many faces are embedded in
    the font file.
  </ul>
  <p>

  <h4>b. From memory:</h4>
  <ul>
    In the case where you have already loaded the font file in memory, you
    can similarly create a new face object for it by calling
    <tt>FT_New_Memory_Face</tt> as in:
    <p>
    <font color="blue"><pre>

      FT_Library   library;   /* handle to library     */
      FT_Face      face;      /* handle to face object */

      error = FT_Init_FreeType( &library );
      if (error) { ..... }

      error = FT_New_Memory_Face( library,
                                  buffer,    /* first byte in memory */
                                  size,      /* size in bytes        */
                                  0,         /* face_index           */
                                  &face );
      if (error) { ... }
    </pre></font>
    <p>
    As you can see, <tt>FT_New_Memory_Face</tt> simply takes a pointer to
    the font file buffer and its size in bytes instead of a file pathname.
    Other than that, it has exactly the same semantics than
    <tt>FT_New_Face</tt>.
  </ul>
  <p>

  <h4>c. From other sources: (compressed files, network, etc..)</h4>
  <ul>
    There are cases where using a filepathname or preloading the file in
    memory is simply not enough. With FreeType 2, it is possible to provide
    your own implementation of i/o routines.
    <p>
    This is done through the <tt>FT_Open_Face</tt> function, which can be
    used to open a new font face with a custom input stream, select a specific
    driver for opening, or even pass extra parameters to the font driver
    when creating the object. We advise you to refer to the FreeType 2
    Reference in order to learn how to use it.
    <p>
  </ul>
  <p>
</ul>

<p><hr><p>

<h3>4. Accessing face content:</h3>
<ul>
  A <em>face object</em> models all information that globally describes
  the face. Usually, this data can be accessed directly by dereferencing
  a handle, like :
  <p>
  <table cellpadding=5>
  <tr valign="top">
     <td><tt><b>face&minus;>num_glyphs</b></tt>
     <td>gives the number of <em>glyphs</em> available in the font face. A glyph
         is simply a character image. It doesn't necessarily correspond to
         a <em>character code</em> though.

  <tr valign="top">
     <td><tt><b>face&minus;>flags</b></tt>
     <td>a 32-bit integer containing bit flags used to describe some face
         properties. For example, the flag <tt>FT_FACE_FLAG_SCALABLE</tt> is
         used to indicate that the face's font format is scalable and that
         glyph images can be rendered for all character pixel sizes. For more
         information on face flags, please read the <a href="#">FreeType API
         Reference</a>

  <tr valign="top">
     <td><tt><b>face&minus;>units_per_EM</b></tt>
     <td>This field is only valid for scalable formats (it is set to 0
         otherwise). It indicates the number of font units covered by the
         EM.

  <tr valign="top">
     <td><tt><b>face&minus;>num_fixed_sizes</b></tt>
     <td>this field gives the number of embedded bitmap <em>strikes</em> in
         the current face. A <em>strike</em> is simply a series of glyph
         images for a given character pixel size. For example, a font face
         could include strikes for pixel sizes 10, 12 and 14. Note that even
         scalable font formats can embedded bitmap strikes !

  <tr valign="top">
     <td><tt><b>face&minus;>fixed_sizes</b></tt>
     <td>this is a pointer to an array of <tt>FT_Bitmap_Size</tt> element.
         each <tt>FT_Bitmap_Size</tt> indicates the horizontal and vertical
         <em>pixel sizes</em> for each of the strikes that are present in the face.

  </table>
  <p>
  For a complete listing of all face properties and fields, please read
  the <a href="#">FreeType 2 API Reference</a>.
  <p>
</ul>

<p><hr><p>
<h3>5. Setting the current pixel size:</h3>
<ul>
  A face object also holds a handle to a <em>size object</em> in its
  <tt>face->size</tt> field. The <em>size</em> object is used to model
  all information for the face that is relative to a given character
  size.
  <p>
  When a new face object is created, its size object defaults to the
  character size of 10 pixels (both horizontall and vertically) for
  scalable formats. For fixed-sizes formats, the size is more or less
  undefined, which is why you must set it before trying to load a
  glyph.
  <p>
  To do that, simply call <tt>FT_Set_Char_Size</tt>. Here's an example
  where the character size is set to 16 pts for a 300x300 dpi device:
  <p>
  <font color="blue"><pre>
        error = FT_Set_Char_Size( face,    /* handle to face object           */
                                  0,       /* char_width in 1/64th of points  */
                                  16*64,   /* char_height in 1/64th of points */
                                  300,     /* horizontal device resolution    */
                                  300 );   /* vertical device resolution      */
  </pre></font>
  <p>
  You'll notice that:<p>
  <ul>
     <li>The character width and heights are specified in 1/64th of points.<p>

     <li>The horizontal and vertical device resolutions are expressed in
         <em>dots-per-inch</em>, or <em>dpi</em>. You can use 72 or 96 dpi
         for display devices like the screen.<p>

     <li>A value of 0 for the character width means "<em>same as character
         height</em>", a value of 0 for the character height means
         "<em>same as character width</em>". Otherwise, it is possible to
         specify different char width and height.<p>

     <li>Using a value of 0 for the horizontal or vertical resolution means
         72 dpi, which is the default.
	 <p>
  </ul>
  <p>
  This function computes the character pixel size that corresponds to the
  character width and height and device resolutions. However, if you want
  to specify the pixel sizes yourself, you can simply call
  <tt>FT_Set_Pixel_Sizes</tt>, as in:
  <p>
  <font color="blue"><pre>
     error = FT_Set_Pixel_Sizes( face,   /* handle to face object            */
                                 0,      /* pixel_width                      */
                                 16 );   /* pixel_height                     */
  </pre></font>
  <p>
  This example will set the character pixel sizes to 16x16 pixels. As
  previously, a value of 0 for one of the dimensions means "<em>same as
  the other</em>".
  <p>
  Note that both functions return an error code. Usually, an error occurs
  with a fixed-size font format (like FNT or PCF) when trying to set the
  pixel size to a value that is not listed in the
  <tt><b>face->fixed_sizes</b></tt> array.
</ul>

<p><hr><p>

<h3>6. Loading a glyph image:</h3>
<ul>
  <h4>a. Converting a character code into a glyph index:</h4>
  <ul>
     Usually, an application wants to load a glyph image based on its
     <em>character code</em>, which is a unique value that defines the
     character for a given <em>encoding</em>. For example, the character
     code 65 represents the 'A' in the ASCII encoding.
     <p>
     A face object contains one or more tables, called <em>charmaps</em>,
     that are used to convert character codes to glyph indices. For example,
     most TrueType fonts contain two charmaps. One is used to convert Unicode
     character codes to glyph indices, the other is used to convert
     Apple Roman encoding into glyph indices. Such fonts can then be used
     either on Windows (which uses Unicode) and Macintosh (which uses
     Apple Roman, bwerk..). Note also that a given charmap might not map to all
     the glyphs present in the font.
     <p>
     By default, when a new face object is created, it lists all the charmaps
     contained in the font face and selects the one that supports Unicode
     character codes if it finds one. Otherwise, it tries to find support for
     Latin-1, then ASCII.
     <p>
     We'll describe later how to look for specific charmaps in a face. For
     now, we'll assume that the face contains at least a Unicode charmap that
     was selected during <tt>FT_New_Face</tt>. To convert a Unicode character
     code to a font glyph index, we use <tt>FT_Get_Char_Index</tt> as in:
     <p>
     <font color="blue"><pre>
         glyph_index = FT_Get_Char_Index( face, charcode );
     </pre></font>
     <p>
     This will look the glyph index corresponding to the given <tt>charcode</tt>
     in the charmap that is currently selected for the face. If charmap is
     selected, the function simply returns the charcode.
     <p>
     Note that this is one of the rare FreeType functions that do not return
     an error code. However, when a given character code has no glyph image in
     the face, the value 0 is returned. By convention, it always correspond to
     a special glyph image called the <b>missing glyph</b>, which usually is
     represented as a box or a space.
     <p>
  </ul>
  <p>

  <h4>b. Loading a glyph from the face:</h4>
  <ul>
     Once you have a glyph index, you can load the corresponding glyph image.
     Note that the glyph image can be in several formats. For example, it will
     be a bitmap for fixed-size formats like FNT, FON or PCF. It will also
     be a scalable vector outline for formats like TrueType or Type 1. The
     glyph image can also be stored in an alternate way that is not known
     at the time of writing this documentation.
     <p>
     The glyph image is always stored in a special object called a
     <em>glyph slot</em>. As it names suggests, a glyph slot is simply a
     container that is able to hold one glyph image at a time, be it a bitmap,
     an outline, or something else. Each face object has a single glyph slot
     object that can be accessed as <b><tt>face&minus;&gt;glyph</tt></b>.
     <p>
     Loading a glyph image into the slot is performed by calling
     <tt>FT_Load_Glyph</tt> as in:
     <p>
     <font color="blue"><pre>
        error = FT_Load_Glyph( face,          /* handle to face object */
                               glyph_index,   /* glyph index           */
                               load_flags );  /* load flags, see below */
     </pre></font>
     <p>
     The <tt>load_flags</tt> value is a set of bit flags used to indicate
     some special operations. The default value <tt>FT_LOAD_DEFAULT</tt> is
     0. The function performs the following :<p>
     <ul>
         <li>if there is a bitmap for the corresponding glyph and size, load
             it in the glyph slot, unless the <tt>FT_LOAD_NO_BITMAP</tt> flag
             is set. This is even <em>true</em> for scalable formats (embedded
             bitmaps are favored over outlines as they usually correspond to
             higher-quality images of the same glyph).
             <p>

         <li>if there is an outline for the corresponding glyph, load it
             unless <tt>FT_LOAD_NO_OUTLINE</tt> is set. Otherwise, scale it
             to the current size, unless the <tt>FT_LOAD_NO_SCALE</tt> flag
             is set.
             <p>

         <li>if the outline was loaded and scaled, try to grid-fit it (which
             dramatically improves its quality) unless the flag
             <tt>FT_LOAD_NO_HINTING</tt> is set.
     </ul>
     <p>
     There are a few others <tt>FT_LOAD_xxx</tt> flags defined. For more
     details see the <a href="#">FreeType 2 API Reference</a>.
  </ul>
  <p>

  <h4>c. Using other charmaps:</h4>
  <ul>
    As said before, when a new face object is created, it will look for
    a Unicode, Latin-1 or ASCII charmap and select it. The currently
    selected charmap is accessed via <b><tt>face&minus;&gt;charmap</tt></b>. This
    field is NULL when no charmap is selected, which typically happen when you
    create a new <tt>FT_Face</tt> object from a font file that doesn't contain
    an ASCII, Latin-1 or Unicode charmap (rare stuff).
    <p>
    The fields <b><tt>face&minus;&gt;num_charmaps</tt></b> and
    <b><tt>face&minus;&gt;charmaps</tt></b> (notice the 's') can be used by
    client applications to look at what charmaps are available in a given
    face.
    <p>
    <b><tt>face&minus;&gt;charmaps</tt></b> is an array of <em>pointers</em>
    to the <tt><b>face&minus;&gt;num_charmaps</b></tt> charmaps contained in the
    font face.
    <p>
    Each charmap has a few visible fields used to describe it in more details.
    For example, <tt><b>charmap->encoding</b></tt> is an enumeration type
    that describes the charmap with FreeType codes. One can also look at
    <tt><b>charmap->platform_id</b></tt> and
    <tt><b>charmap->encoding_id</b></tt> for more exotic needs.
    <p>
    Here's an example code that looks for a chinese Big5 charmap then
    selects it via <tt>FT_Set_CharMap</tt>:
    <p>
    <font color="blue"><pre>
        FT_CharMap  found = 0;
        FT_CharMap  charmap;
        int         n;

        for ( n = 0; n &lt; face-&gt;num_charmaps; n++ )
        {
          charmap = face&gt;charmaps[n];
          if (charmap->encoding == ft_encoding_big5)
          {
            found = charmap;
            break;
          }
        }

        if (!found) { ... }

        /* now, select the charmap for the face object */
        error = FT_Set_CharMap( face, found );
        if (error) { .... }
    </pre></font>
    <p>
    One might now call <tt>FT_Get_Char_Index</tt> with Big5 character codes
    to retrieve glyph indices.
    <p>
  </ul>
  <p>
</ul>

<p><hr><p>

<h3>7. Accessing glyph image data:</h3>
<ul>
  Glyph image data is accessible through <tt><b>face&minus;&gt;glyph</b></tt>.
  See the definition of the <tt>FT_GlyphSlot</tt> type for more details. As
  stated previously, each face has a single glyph slot, where <em>one</em> glyph
  image <em>at a time</em> can be loaded. Each time you call
  <tt>FT_Load_Glyph</tt>, you erase the content of the glyph slot with a new
  glyph image.
  <p>
  Note however that the glyph slot object itself doesn't change, only its
  content, which means that you can perfectly create a "shortcut" to access
  it as in:
  <p>
  <font color="blue"><pre>
     {
       FT_GlyphSlot  glyph = face->glyph;  /* shortcut to glyph slot */

       for ( n = 0; n &lt; face->num_glyphs; n++ )
       {
         .... load glyph n...
         .... access glyph data as glyph-&gt;xxxx
       }
     }
  </pre></font>
  <p>
  The <tt>glyph</tt> variable will be valid until its parent <tt>face</tt>
  is destroyed. Here are a few important fields of the glyph slot:
  <p>
  <table cellpadding=10>
    <tr valign="top">
       <td><tt><b>glyph&minus;&gt;format</b></tt>
       <td>Indicates the type of the loaded glyph image. Can be either
           <tt>ft_glyph_format_bitmap</tt>, <tt>ft_glyph_format_outline</tt>
           or other values.

    <tr valign="top">
       <td><tt><b>glyph&minus;&gt;metrics</b></tt>
       <td>A simple structure used to hold the glyph image's metrics. Note
           that <em>most distances are expressed in 1/64th of pixels !</em>
           See the API reference or User Guide for a description of the
           <tt>FT_Glyph_Metrics</tt> structure.

    <tr valign="top">
       <td><tt><b>glyph&minus;&gt;bitmap</b></tt>
       <td>When the glyph slot contains a bitmap, a simple <tt>FT_Bitmap</tt>
           that describes it. See the API reference or user guide for a
           description of the <tt>FT_Bitmap</tt> structure.

    <tr valign="top">
       <td><tt><b>glyph&minus;&gt;outline</b></tt>
       <td>When the glyph slot contains a scalable outline, this structure
           describes it. See the definition of the <tt>FT_Outline</tt>
           structure.
  </table>
  <p>
</ul>

<h3>8. Rendering glyph outlines into bitmaps:</h3>
<ul>
  You can easily test the format of the glyph image by inspecting the
  <tt>face->glyph->format</tt> variable. If its value is
  <tt>ft_glyph_format_bitmap</tt>, the glyph image that was loaded is
  a bitmap that can be directly blit to your own surfaces through your
  favorite graphics library (FreeType 2 doesn't provide bitmap blitting
  routines, as you may imagine :-)
  <p>
  On the other hand, when the format if <tt>ft_glyph_format_outline</tt>
  or something else, the library provides a means to convert such glyph
  images to bitmaps through what are called <b>rasters</b>.
  <p>


  On the other hand, when the image is a scalable outline, or something else,
  FreeType provides a function to convert the glyph image into a
  pre-existing bitmap that you'll handle to it, named
  <tt>FT_Get_Glyph_Bitmap</tt>. Here's a <em>simple</em> example code
  that renders an outline into a <b>monochrome</b> bitmap :
  <p>
  <font color="blue"><pre>
     {
       FT_GlyphSlot  glyph;

       .... load glyph ...

       glyph = face-&gt;glyph;   /* shortcut to glyph data */
       if (glyph->format == ft_glyph_format_outline )
       {
         FT_Bitmap  bit;

         /* set-up a bitmap descriptor for our target bitmap */
         bit.rows       = bitmap_height;
         bit.width      = bitmap_width;
         bit.pitch      = bitmap_row_bytes;
         bit.pixel_mode = ft_pixel_mode_mono;  /* render into a mono bitmap */
         bit.buffer     = bitmap_buffer;

         /* render the outline directly into the bitmap */
         error = FT_Get_Glyph_Bitmap( face, &bit );
         if (error) { ... }
       }
     }
  </pre></font>
  <p>
  You should note that <b><em><tt>FT_Get_Glyph_Bitmap</tt> doesn't create the
  bitmap.</em></b> It only needs a descriptor, of type <tt>FT_Bitmap</tt>,
  and writes directly into it.
  <p>
  Note that the FreeType scan-converter for outlines can also generate
  anti-aliased glyph bitmaps with 128 level of grays. For now, it is
  restricted to rendering to 8-bit gray-level bitmaps, though this may
  change in the future. Here's some code to do just that:
  <p>
  <font color="blue"><pre>
     {
       FT_GlyphSlot  glyph;

       .... load glyph ...

       glyph = face-&gt;glyph;   /* shortcut to glyph data */
       if (glyph->format == ft_glyph_format_outline )
       {
         FT_Bitmap  bit;

         /* set-up a bitmap descriptor for our target bitmap */
         bit.rows       = bitmap_height;
         bit.width      = bitmap_width;
         bit.pitch      = bitmap_row_bytes;
         bit.pixel_mode = ft_pixel_mode_gray;  /* 8-bit gray-level bitmap */
         bit.grays      = 128;                 /* MUST be 128 for now     */
         bit.buffer     = bitmap_buffer;

         /* clean the bitmap - IMPORTANT */
         memset( bit.buffer, 0, bit.rows*bit.pitch );

         /* render the outline directly into the bitmap */
         error = FT_Get_Glyph_Bitmap( face, &bit );
         if (error) { ... }
       }
     }
  </pre></font>
  <p>
  You'll notice that :<p>
  <ul>
     <li>As previously, <tt>FT_Get_Glyph_Bitmap</tt> doesn't generate the
         bitmap, it simply renders to it.<p>

     <li>The target bitmap must be cleaned before calling the function. This
         is a limitation of our current anti-aliasing algorithm and is
         EXTREMELY important.<p>

     <li>The anti-aliaser uses 128 levels of grays exclusively for now (this
         will probably change in a near future). This means that you <b>must</b>
         set <tt>bit.grays</tt> to 128. The generated image uses values from
         0 (back color) to 127 (foreground color).
         <p>

     <li>It is <b>not</b> possible to render directly an anti-aliased outline into
         a pre-existing gray-level bitmap, or even any colored-format one
         (like RGB16 or paletted 8-bits). We will not discuss this issue in
         great details here, but the reason is that we do not want to deal
         with graphics composition (or alpha-blending) within FreeType.
  </ul>
  <p>
  </ul>
</ul>

</td></tr></table>
</center>
<p><hr>