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first updates to the tutorial. This is step 1 (fairly basic stuff)

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<!doctype html public "-//w3c//dtd html 4.0 transitional//en">
<html>
<head>
<meta http-equiv="Content-Type"
content="text/html; charset=iso-8859-1">
<meta name="Author"
content="David Turner">
<title>FreeType 2 Tutorial</title>
</head>
<body text="#000000"
bgcolor="#FFFFFF"
link="#0000EF"
vlink="#51188E"
alink="#FF0000">
<h1 align=center>
FreeType 2.0 Tutorial<br>
Step 1 - simple glyph loading
</h1>
<h3 align=center>
&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>
<table width="70%">
<tr><td>
<hr>
<h2>
Introduction
</h2>
<p>This is the first section of the FreeType 2 tutorial. It will teach
you to do the following:</p>
<ul>
<li>initialise the library</li>
<li>open a font file by creating a new face object</li>
<li>select a character size in points or in pixels</li>
<li>load a single glyph image and convert it to a bitmap</li>
<li>render a very simple string of text</li>
<li>render a rotated string of text easily</li>
</ul>
<hr>
<h3>
1. Header files
</h3>
<p>To include the main FreeType header file, simply say</p>
<font color="blue">
<pre>
#include &lt;freetype/freetype.h&gt;</pre>
</font>
<p>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.</p>
<hr>
<h3>
2. Initialize the library
</h3>
<p>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</p>
<font color="blue">
<pre>
#include &lt;freetype/freetype.h&gt;
FT_Library library;
...
{
...
error = FT_Init_FreeType( &library );
if ( error )
{
... an error occurred during library initialization ...
}
}</pre>
</font>
<p>This function is in charge of the following:</p>
<ul>
<li>
<p>Creating a new instance of the FreeType&nbsp;2 library, and set
the handle <tt>library</tt> to it.</p>
</li>
<li>
<p>Load each modules that FreeType knows about in the library.
This means that by default, your new <tt>library</tt> object is able
to handle TrueType, Type&nbsp;1, CID-keyed & OpenType/CFF fonts
gracefully.</p>
</li>
</ul>
<p>As you can see, the function returns an error code, like most others
in the FreeType API. An error code of&nbsp;0 <em>always</em> means that
the operation was successful; otherwise, the value describes the error,
and <tt>library</tt> is set to NULL.</p>
<hr>
<h3>
3. Load a font face
</h3>
<h4>
a. From a font file
</h4>
<p>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 or read, or simply that it is broken...
}</pre>
</font>
<p>As you can certainly imagine, <tt>FT_New_Face</tt> opens a font
file, then tries to extract one face from it. Its parameters are</p>
<table cellpadding=5>
<tr valign="top">
<td>
<tt><b>library</b></tt>
</td>
<td>
<p>handle to the FreeType library instance where the face object
is created</p>
</td>
</tr>
<tr valign="top">
<td>
<tt><b>filepathname</b></tt>
</td>
<td>
<p>the font file pathname (standard C string).</p>
</td>
</tr>
<tr valign="top">
<td>
<tt><b>face_index</b></tt>
</td>
<td>
<p>Certain font formats allow several font faces to be embedded
in a single file.</p>
<p>This index tells which face you want to load. An error will
be returned if its value is too large.</p>
<p>Index 0 always work though.</p>
</td>
</tr>
<tr valign="top">
<td>
<tt><b>face</b></tt>
</td>
<td>
<p>A <em>pointer</em> to the handle that will be set to describe
the new face object.</p>
<p>It is set to NULL in case of error.</p>
</td>
</tr>
</table>
<p>To know 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.</p>
<h4>
b. From memory
</h4>
<p>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 as
<tt>FT_New_Face()</tt>.</p>
<h4>
c. From other sources (compressed files, network, etc.)
</h4>
<p>There are cases where using a file pathname or preloading the file
in memory is simply not enough. With FreeType&nbsp;2, it is possible
to provide your own implementation of i/o routines.</p>
<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&nbsp;2 reference manual in order to learn how to use it.</p>
<p>Note that providing a custom stream might also be used to access a
TrueType font embedded in a Postscript Type&nbsp;42 wrapper.</p>
<hr>
<h3>
4. Accessing face content
</h3>
<p>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->num_glyphs</b></tt>
</td>
<td>
<p>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.</p>
</td>
</tr>
<tr valign="top">
<td>
<tt><b>face->flags</b></tt>
</td>
<td>
<p>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&nbsp;2 API Reference</a>.</p>
</td>
</tr>
<tr valign="top">
<td>
<tt><b>face->units_per_EM</b></tt>
</td>
<td>
<p>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.</p>
</td>
</tr>
<tr valign="top">
<td>
<tt><b>face->num_fixed_sizes</b></tt>
</td>
<td>
<p>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&nbsp;14. Note that even scalable font formats can have
embedded bitmap strikes!</p>
</td>
</tr>
<tr valign="top">
<td>
<tt><b>face->fixed_sizes</b></tt>
</td>
<td>
<p>this is a pointer to an array of <tt>FT_Bitmap_Size</tt>
elements. 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.</p>
</td>
</tr>
</table>
<p>For a complete listing of all face properties and fields, please read
the <a href="#">FreeType&nbsp;2 API Reference</a>.<p>
<hr>
<h3>
5. Setting the current pixel size
</h3>
<p>FreeType 2 uses "<em>size objects</em>" to model all
information related to a given character size for a given face.
For example, a size object will hold the value of certain metrics
like the ascender or text height, expressed in 1/64th of a pixel,
for a character size of 12 points.</p>
<p>When the <tt>FT_New_Face</tt> function is called (or one of its
cousins), it <b>automatically</b> creates a new size object for
the returned face. This size object is directly accessible as
<b><tt>face->size</tt></b>.</p>
<p><em>NOTA BENE: a single face object can deal with one or more size
objects at a time, however, this is something that few programmers
really need to do. We have thus have decided to simplify the API for
the most common use (i.e. one size per face), while keeping this
feature available through additional fuctions.</em></p>
<p>When a new face object is created, its size object defaults to the
character size of 10&nbsp;pixels (both horizontally 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>
<p>To do that, simply call <tt>FT_Set_Char_Size()</tt>. Here is an
example where the character size is set to 16pt for a 300x300&nbsp;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 will notice that:</p>
<ul>
<li>
<p>The character width and heights are specified in 1/64th of
points. A point is a <em>physical</em> distance, equaling 1/72th
of an inch, it's not a pixel..<p>
</li>
<li>
<p>The horizontal and vertical device resolutions are expressed in
<em>dots-per-inch</em>, or <em>dpi</em>. You can use 72 or
96&nbsp;dpi for display devices like the screen. The resolution
is used to compute the character pixel size from the character
point size.</p>
</li>
<li>
<p>A value of&nbsp;0 for the character width means "<em>same as
character height</em>", a value of&nbsp;0 for the character height
means "<em>same as character width</em>". Otherwise, it is possible
to specify different char widths and heights.</p>
</li>
<li>
<p>Using a value of 0 for the horizontal or vertical resolution means
72&nbsp;dpi, which is the default.</p>
</li>
<li>
<p>The first argument is a handle to a face object, not a size
object. That's normal, and must be seen as a convenience.</p>
</li>
</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&nbsp;pixels.
As previously, a value of&nbsp;0 for one of the dimensions means
"<em>same as the other</em>".</p>
<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.</p>
<hr>
<h3>
6. Loading a glyph image
</h3>
<h4>
a. Converting a character code into a glyph index
</h4>
<p>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&nbsp;65 represents the `A' in ASCII encoding.</p>
<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>
<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>
<p>We will describe later how to look for specific charmaps in a face.
For now, we will 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>
<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&nbsp;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>
<h4>
b. Loading a glyph from the face
</h4>
<p>Once you have a glyph index, you can load the corresponding glyph
image. The latter can be stored in various formats within the font file.
For fixed-size formats like FNT or PCF, each image is a bitmap. Scalable
formats like TrueType or Type 1 use vectorial shapes, named "outlines"
to describe each glyph. Some formats may have even more exotic ways
of representing glyph (e.g. MetaFont). Fortunately, FreeType 2 is
flexible enough to support any kind of glyph format through
a simple API.</p>
<p>The glyph image is always stored in a special object called a
<em>glyph slot</em>. As its name 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->glyph</tt></b>.</p>
<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&nbsp;0.</p>
<p>This function will try to load the corresponding glyph image
from the face. Basically, this means that:</p>
<ul>
<li>
<p>If a bitmap is found for the corresponding glyph and pixel
size, it will be loaded into the slot (embedded bitmaps are always
favored over native image formats, because we assume that
they are higher-quality versions of the same glyph. This
can be ignored by using the FT_LOAD_NO_BITMAP flag)</p>
</li>
<li>
<p>Otherwise, a native image for the glyph will be loaded.
It will also be scaled to the current pixel size, as
well as hinted for certain formats like TrueType and
Type1.</p>
</li>
</ul>
<p>The field <tt><b>glyph->format</b></tt> describe the format
used to store the glyph image in the slot. If it is not
<tt>ft_glyph_format_bitmap</tt>, one can immediately
convert it to a bitmap through <tt>FT_Render_Glyph</tt>,
as in:</p>
<font color="blue">
<pre>
error = FT_Render_Glyph(
face->glyph, /* glyph slot */
render_mode ); /* render mode */
</pre>
</font>
<p>The parameter <tt>render_mode</tt> is a set of bit flags used
to specify how to render the glyph image. Set it to 0 to render
a monochrome bitmap, or to <tt>ft_render_mode_antialias</tt> to
generate a high-quality (256 gray levels) anti-aliased bitmap
from the glyph image.</p>
<p>Once you have a bitmapped glyph image, you can access it directly
through <tt><b>glyph->bitmap</b></tt> (a simple bitmap descriptor),
and position it through <tt><b>glyph->bitmap_left</b></tt> and
<tt><b>glyph->bitmap_top</b></tt>.</p>
<p>Note that <tt>bitmap_left</tt> is the horizontal distance from the
current pen position to the left-most border of the glyph bitmap,
while <tt>bitmap_top</tt> is the vertical distance from the
pen position (on the baseline) to the top-most border of the
glyph bitmap. <em>It is positive to indicate an upwards
distance</em>.</p>
<p>The next section will detail the content of a glyph slot and
how to access specific glyph information (including metrics).</p>
<h4>
c. Using other charmaps
</h4>
<p>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->charmap</tt></b>. This
field is NULL when no charmap is selected, which typically happens
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>
<p>There are two ways to select a different charmap with FreeType 2.
The easiest is when the encoding you need already has a corresponding
enumeration defined in <tt>&lt;freetype/freetype.h&gt;</tt>, as
<tt>ft_encoding_big5</tt>. In this case, you can simply call
<tt>FT_Select_CharMap</tt> as in:</p>
<font color="blue"><pre>
error = FT_Select_CharMap(
face, /* target face object */
ft_encoding_big5 ); /* encoding.. */
</pre></font>
<p>Another way is to manually parse the list of charmaps for the
face, this is accessible through the fields
<tt><b>num_charmaps</b></tt> and <tt><b>charmaps</b></tt>
(notice the 's') of the face object. As you could expect,
the first is the number of charmaps in the face, while the
second is <em>a table of pointers to the charmaps</em>
embedded in the face.</p>
<p>Each charmap has a few visible fields used to describe it more
precisely. Mainly, one will look at
<tt><b>charmap->platform_id</b></tt> and
<tt><b>charmap->encoding_id</b></tt> that define a pair of
values that can be used to describe the charmap in a rather
generic way.</p>
<p>Each value pair corresponds to a given encoding. For example,
the pair (3,1) corresponds to Unicode. Their list is
defined in the TrueType specification but you can also use the
file <tt>&lt;freetype/ftnameid.h&gt;</tt> which defines several
helpful constants to deal with them..</p>
<p>To look for a specific encoding, you need to find a corresponding
value pair in the specification, then look for it in the charmaps
list. Don't forget that some encoding correspond to several
values pair (yes it's a real mess, but blame Apple and Microsoft
on such stupidity..). Here's some code to do it:</p>
<font color="blue">
<pre>
FT_CharMap found = 0;
FT_CharMap charmap;
int n;
for ( n = 0; n &lt; face->num_charmaps; n++ )
{
charmap = face->charmaps[n];
if ( charmap->platform_id == my_platform_id &&
charmap->encoding_id == my_encoding_id )
{
found = charmap;
break;
}
}
if ( !found ) { ... }
/* now, select the charmap for the face object */
error = FT_Set_CharMap( face, found );
if ( error ) { ... }</pre>
</font>
<p>Once a charmap has been selected, either through
<tt>FT_Select_CharMap</tt> or <tt>FT_Set_CharMap</tt>,
it is used by all subsequent calls to
<tt>FT_Get_Char_Index()</tt>.</p>
<h4>
d. Glyph Transforms:
</h4>
<p>It is possible to specify an affine transformation to be applied
to glyph images when they're loaded. Of course, this will only
work for scalable (vectorial) font formats.</p>
<p>To do that, simply call <tt>FT_Set_Transform</tt>, as in:</p>
<font color="blue"><pre>
error = FT_Set_Transform(
face, /* target face object */
&amp;matrix, /* pointer to 2x2 matrix */
&amp;delta ); /* pointer to 2d vector */
</pre></font>
<p>This function will set the current transform for a given face
object. Its second parameter is a pointer to a simple
<tt>FT_Matrix</tt> structure that describes a 2x2 affine matrix.
The third parameter is a pointer to a <tt>FT_Vector</tt> structure
that describe a simple 2d vector that is used to translate the
glyph image <em>after</em> the 2x2 transform.</p>
<p>Note that the matrix pointer can be set to NULL, (in which case
the identity transform will be used). Coefficients of the matrix
are otherwise in 16.16 fixed float units.</p>
<p>The vector pointer can also be set to NULL (in which case a delta
of (0,0) will be used). The vector coordinates are expressed in
1/64th of a pixel (also known as 26.6 fixed floats).</p>
<p><em>NOTA BENE: The transform is applied every glyph that is loaded
through <tt>FT_Load_Glyph</tt>. Note that loading a glyph bitmap
with a non-trivial transform will produce an error..</em></p>
<hr>
<h3>
7. Simple Text Rendering:
</h3>
<p>We will now present you with a very simple example used to render
a string of 8-bit Latin-1 text, assuming a face that contains a
Unicode charmap</p>
<p>The idea is to create a loop that will, on each iteration, load one
glyph image, convert it to an anti-aliased bitmap, draw it on the
target surface, then increment the current pen position</p>
<h4>a. basic code :</h4>
<p>The following code performs our simple text rendering with the
functions previously described.</p>
<font color="blue"><pre>
FT_GlyphSlot slot = face->glyph; // a small shortcut
int pen_x, pen_y, n;
.. initialise library ..
.. create face object ..
.. set character size ..
pen_x = 300;
pen_y = 200;
for ( n = 0; n &lt; num_chars; n++ )
{
FT_UInt glyph_index;
// retrieve glyph index from character code
glyph_index = FT_Get_Char_Index( face, text[n] );
// load glyph image into the slot (erase previous one)
error = FT_Load_Glyph( face, glyph_index, FT_LOAD_DEFAULT );
if (error) continue; // ignore errors
// convert to an anti-aliased bitmap
error = FT_Render_Glyph( face->glyph, ft_render_mode_antialias );
if (error) continue;
// now, draw to our target surface
my_draw_bitmap( &slot->bitmap,
pen_x + slot->bitmap_left,
pen_y - slot->bitmap_top );
// increment pen position
pen_x += slot->advance.x >> 6;
pen_y += slot->advance.y >> 6; // unuseful for now..
}
</pre></font>
<p>This code needs a few explanations:</p>
<ul>
<li><p>
we define a handle named <tt>slot</tt> that points to the
face object's glyph slot. (the type <tt>FT_GlyphSlot</tt> is
a pointer). That's a convenience to avoid using
<tt>face->glyph->XXX</tt> every time.
</p></li>
<li><p>
we increment the pen position with the vector <tt>slot->advance</tt>,
which correspond to the glyph's <em>advance width</em> (also known
as its <em>escapement</em>). The advance vector is expressed in
64/th of pixels, and is truncated to integer pixels on each
iteration.</p>
</p></li>
<li><p>
The function <tt>my_draw_bitmap</tt> is not part of FreeType, but
must be provided by the application to draw the bitmap to the target
surface. In this example, it takes a pointer to a FT_Bitmap descriptor
and the position of its top-left corner as arguments.
</p></li>
<li><p>
The value of <tt>slot->bitmap_top</tt> is positive for an
<em>upwards</em> vertical distance. Assuming that the coordinates
taken by <tt>my_draw_bitmap</tt> use the opposite convention
(increasing Y corresponds to downwards scanlines), we substract
it to <tt>pen_y</tt>, instead of adding it..
</p></li>
</ul>
<h4>b. refined code:</h4>
<p>The following code is a refined version of the example above. It
uses features and functions of FreeType 2 that have not yet been
introduced, and they'll be explained below:</p>
<font color="blue"><pre>
FT_GlyphSlot slot = face->glyph; // a small shortcut
FT_UInt glyph_index;
int pen_x, pen_y, n;
.. initialise library ..
.. create face object ..
.. set character size ..
pen_x = 300;
pen_y = 200;
for ( n = 0; n &lt; num_chars; n++ )
{
// load glyph image into the slot (erase previous one)
error = FT_Load_Char( face, text[n], FT_LOAD_RENDER | FT_LOAD_ANTI_ALIAS );
if (error) continue; // ignore errors
// now, draw to our target surface
my_draw_bitmap( &slot->bitmap,
pen_x + slot->bitmap_left,
pen_y - slot->bitmap_top );
// increment pen position
pen_x += slot->advance.x >> 6;
}
</pre></font>
<p>We've reduced the size of our code, but it does exactly the same thing,
as:</p>
<ul>
<li><p>
We use the function <tt><b>FT_Load_Char</b></tt> instead of
<tt>FT_Load_Glyph</tt>. As you probably imagine, it's equivalent
to calling <tt>FT_Get_Char_Index</tt> then <tt>FT_Get_Load_Glyph</tt>.
</p></li>
<li><p>
We do not use <tt>FT_LOAD_DEFAULT</tt> for the loading mode, but
the two bit flags <tt><b>FT_LOAD_RENDER</b></tt> and
<tt><b>FT_LOAD_ANTI_ALIAS</b></tt>. The first flag indicates that
the glyph image must be immediately converted to a bitmap, and
the second that it should be renderer anti-aliased. Of course, this
is also a shortcut that avoids calling <tt>FT_Render_Glyph</tt>
explicitely but is strictly equivalent..
</p></li>
</ul>
<h4>c. more advanced rendering:</h4>
<p>Let's try to render transformed text now (for example through a
rotation). We can do this using <tt>FT_Set_Transform</tt>. Here's
how to do it:</p>
<font color="blue"><pre>
FT_GlyphSlot slot = face->glyph; // a small shortcut
FT_Matrix matrix; // transformation matrix
FT_UInt glyph_index;
FT_Vector pen; // untransformed origin
int pen_x, pen_y, n;
.. initialise library ..
.. create face object ..
.. set character size ..
// set up matrix
matrix.xx = (FT_Fixed)( cos(angle)*0x10000);
matrix.xy = (FT_Fixed)(-sin(angle)*0x10000);
matrix.yx = (FT_Fixed)( sin(angle)*0x10000);
matrix.yy = (FT_Fixed)( cos(angle)*0x10000);
// the pen position in 26.6 cartesian space coordinates
pen.x = 300 * 64;
pen.y = ( my_target_height - 200 ) * 64;
for ( n = 0; n &lt; num_chars; n++ )
{
// set transform
FT_Set_Transform( face, &matrix, &pen );
// load glyph image into the slot (erase previous one)
error = FT_Load_Char( face, text[n], FT_LOAD_RENDER | FT_LOAD_ANTI_ALIAS );
if (error) continue; // ignore errors
// now, draw to our target surface (convert position)
my_draw_bitmap( &slot->bitmap,
slot->bitmap_left,
my_target_height - slot->bitmap_top );
// increment pen position
pen.x += slot->advance.x;
pen.y += slot->advance.y;
}
</pre></font>
<p>You'll notice that:</p>
<ul>
<li><p>
we now use a vector, of type <tt>FT_Vector</tt> to store the pen
position, with coordinates expressed as 1/64th of pixels, hence
a multiplication. The position is expressed in cartesian space.
</p></li>
<li><p>
glyph images are always loaded, transformed and described in the
cartesian coordinate system in FreeType (which means that
increasing Y corresponds to upper scanlines), unlike the system
typically used for bitmaps (where the top-most scanline has
coordinate 0). We must thus convert between the two systems
when we define the pen position, and when we compute the top-left
position of the bitmap.
</p></li>
<li><p>
we set the transform on each glyph, to indicate the rotation
matrix, as well as a delta that will move the transformed image
to the current pen position (in cartesian space, not bitmap space).
</p></li>
<li><p>
the advance is always returned transformed, which is why it can
be directly added to the current pen position. Note that it is
<b>not</b> rounded this time.
</p></li>
</ul>
<p>It is important to note that, while this example is a bit more
complex than the previous one, it is strictly equivalent
for the case where the transform is the identity.. Hence it can
be used as a replacement (but a more powerful one).</p>
<hr>
<h3>
Conclusion
</h3>
<p>In this first section, you have learned the basics of FreeType 2,
as well as sufficient knowledge to know how to render rotated text.
Woww ! Congratulations..</p>
<p>The next section will dive into more details of the API in order
to let you access glyph metrics and images directly, as well as
how to deal with scaling, hinting, kerning, etc..</p>
<p>The third section will discuss issues like modules, caching and a
few other advanced topics like how to use multiple size objects
with a single face.
</p>
</td></tr>
</table>
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