ref: afc01e884546a954e1276677950a8ad900fb135c
parent: eddd9909e275b997629996d85ccf6abd10fbb493
author: Werner Lemberg <[email protected]>
date: Thu Oct 12 12:09:49 EDT 2000
Completely revised.
--- a/docs/tutorial/step1.html
+++ b/docs/tutorial/step1.html
@@ -1,4 +1,5 @@
-<!doctype html public "-//w3c//dtd html 4.0 transitional//en">
+<!doctype html public "-//w3c//dtd html 4.0 transitional//en"
+ "http://www.w3.org/TR/REC-html40/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type"
@@ -15,19 +16,19 @@
alink="#FF0000">
<h1 align=center>
- FreeType 2.0 Tutorial<br>
- Step 1 - simple glyph loading
+ FreeType 2.0 Tutorial<br>
+ Step 1 -- simple glyph loading
</h1>
<h3 align=center>
- © 2000 David Turner
+ © 2000 David Turner
(<a href="mailto:[email protected]">[email protected]</a>)<br>
- © 2000 The FreeType Development Team
+ © 2000 The FreeType Development Team
(<a href="http://www.freetype.org">www.freetype.org</a>)
</h3>
<center>
-<table width="70%">
+<table width="75%">
<tr><td>
<hr>
@@ -36,11 +37,11 @@
Introduction
</h2>
- <p>This is the first section of the FreeType 2 tutorial. It will teach
- you to do the following:</p>
+ <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>initialize 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>
@@ -63,8 +64,7 @@
<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>
+ <tt>freetype.h</tt>. They will be described later in this tutorial.</p>
<hr>
@@ -86,7 +86,7 @@
{...
- error = FT_Init_FreeType( &library );
+ error = FT_Init_FreeType( &library );
if ( error )
{... an error occurred during library initialization ...
@@ -98,14 +98,14 @@
<ul>
<li>
- <p>Creating a new instance of the FreeType 2 library, and set
- the handle <tt>library</tt> to it.</p>
+ Creating a new instance of the FreeType 2 library, and set the
+ handle <tt>library</tt> to it.
</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 1, CID-keyed & OpenType/CFF fonts
- gracefully.</p>
+ Load each module that FreeType knows about in the library. This
+ means that by default, your new <tt>library</tt> object is able to
+ handle TrueType, Type 1, CID-keyed & OpenType/CFF fonts
+ gracefully.
</li>
</ul>
@@ -124,23 +124,24 @@
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>
+ <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 */
+ FT_Library library; /* handle to library */
+ FT_Face face; /* handle to face object */
- error = FT_Init_FreeType( &library );
+
+ error = FT_Init_FreeType( &library );
if ( error ) { ... }error = FT_New_Face( library,
"/usr/share/fonts/truetype/arial.ttf",
0,
- &face );
+ &face );
if ( error == FT_Err_Unknown_File_Format )
{... the font file could be opened and read, but it appears
@@ -149,11 +150,11 @@
else if ( error )
{... another error code means that the font file could not
- ... be opened or read, or simply that it is broken...
+ ... 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
+ <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>
@@ -162,8 +163,8 @@
<tt><b>library</b></tt>
</td>
<td>
- <p>handle to the FreeType library instance where the face object
- is created</p>
+ <p>a handle to the FreeType library instance where the face
+ object is created</p>
</td>
</tr>
<tr valign="top">
@@ -201,8 +202,8 @@
</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
+ <p>To know how many faces a given font file contains, load its first
+ face (use <tt>face_index</tt>=0), then check the value of
<tt>face->num_faces</tt> which indicates how many faces are embedded
in the font file.</p>
@@ -212,14 +213,15 @@
<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>
+ <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 */
+ FT_Library library; /* handle to library */
+ FT_Face face; /* handle to face object */
- error = FT_Init_FreeType( &library );
+
+ error = FT_Init_FreeType( &library );
if ( error ) { ... }error = FT_New_Memory_Face( library,
@@ -226,7 +228,7 @@
buffer, /* first byte in memory */
size, /* size in bytes */
0, /* face_index */
- &face );
+ &face );
if ( error ) { ... }</pre></font>
@@ -241,7 +243,7 @@
<p>There are cases where using a file pathname 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>
+ 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
@@ -255,7 +257,7 @@
<hr>
<h3>
- 4. Accessing face content
+ 4. Accessing face contents
</h3>
<p>A <em>face object</em> models all information that globally describes
@@ -291,9 +293,9 @@
<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>
+ <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">
@@ -302,11 +304,11 @@
</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 14. Note that even scalable font formats can have
- embedded bitmap strikes!</p>
+ in the current face. A <em>strike</em> is 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 have embedded bitmap
+ strikes!</p>
</td>
</tr>
<tr valign="top">
@@ -314,7 +316,7 @@
<tt><b>face->fixed_sizes</b></tt>
</td>
<td>
- <p>this is a pointer to an array of <tt>FT_Bitmap_Size</tt>
+ <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>
@@ -331,32 +333,32 @@
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>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>When the <tt>FT_New_Face()</tt> function is called (or one of its
+ cousins), it <em>automatically</em> creates a new size object for the
+ returned face. This size object is directly accessible as
+ <tt>face->size</tt>.</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><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 functions.</em></p>
<p>When a new face object is created, its size object defaults to the
- character size of 10 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>
+ character size of 10 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 dpi
- device:</p>
+ example where the character size is set to 16pt for a 300x300 dpi
+ device:</p>
<font color="blue">
<pre>
@@ -363,39 +365,39 @@
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 */
+ 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>
+ <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>
+ 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.
</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 dpi for display devices like the screen. The resolution
- is used to compute the character pixel size from the character
- point size.</p>
+ 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. The resolution is
+ used to compute the character pixel size from the character point
+ size.
</li>
<li>
- <p>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 widths and heights.</p>
+ 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 widths and heights.
</li>
<li>
- <p>Using a value of 0 for the horizontal or vertical resolution means
- 72 dpi, which is the default.</p>
+ Using a value of 0 for the horizontal or vertical resolution
+ means 72 dpi, which is the default.
</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>
+ The first argument is a handle to a face object, not a size object.
+ That's normal, and must be seen as a convenience.
</li>
</ul>
@@ -414,12 +416,12 @@
<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>
+ <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>
+ <tt>face->fixed_sizes></tt> array.</p>
<hr>
@@ -442,7 +444,7 @@
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
+ Macintosh (which uses Apple Roman usually). 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
@@ -461,15 +463,14 @@
glyph_index = FT_Get_Char_Index( face, charcode );</pre>
</font>
- <p>This will look the glyph index corresponding to the given
+ <p>This will look up 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>
+ face.
<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
+ it always corresponds to a special glyph image called the <b>missing
glyph</b>, which usually is represented as a box or a space.</p>
<h4>
@@ -477,20 +478,19 @@
</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>
+ 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 <em>outlines</em> 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
+ <em>glyph slot</em>. As its name suggests, a glyph slot is 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>
+ glyph slot object that can be accessed as <tt>face->glyph</tt>.</p>
<p>Loading a glyph image into the slot is performed by calling
<tt>FT_Load_Glyph()</tt> as in</p>
@@ -507,61 +507,56 @@
indicate some special operations. The default value
<tt>FT_LOAD_DEFAULT</tt> is 0.</p>
- <p>This function will try to load the corresponding glyph image
- from the face. Basically, this means that:</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>
+ <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 changed by
+ using the <tt>FT_LOAD_NO_BITMAP</tt> 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 Type 1.</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>
+ <p>The field <tt>glyph->format</tt> describes the format used to store
+ the glyph image in the slot. If it is not
+ <tt>ft_glyph_format_bitmap</tt>, it is possible to immedialy 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>
+ 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, or the
- equivalent <tt>ft_render_mode_normal</tt> to render a high-quality
- anti-aliased (256 gray levels) bitmap, as this is the default.
- You can alternatively use <tt>ft_render_mode_mono</tt> if you
- want to generate a 1-bit monochrome bitmap.</p>
+ <p>The parameter <tt>render_mode</tt> specifies how to render the
+ glyph image. Set it <tt>ft_render_mode_normal</tt> to render a
+ high-quality anti-aliased (256 gray levels) bitmap. You can
+ alternatively use <tt>ft_render_mode_mono</tt> if you want to generate
+ a 1-bit monochrome bitmap.</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>
+ through <tt>glyph->bitmap</tt> (a simple bitmap descriptor), and
+ position it with <tt>glyph->bitmap_left</tt> and
+ <tt>glyph->bitmap_top</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>
+ 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>
+ <p>The second part of the tutorial will describe the contents of a
+ glyph slot and how to access specific glyph information (including
+ metrics).</p>
<h4>
c. Using other charmaps
@@ -569,50 +564,47 @@
<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>
+ selected charmap is accessed via <tt>face->charmap</tt>. This field
+ is NULL if 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><freetype/freetype.h></tt>, as
- <tt>ft_encoding_big5</tt>. In this case, you can simply call
- <tt>FT_Select_CharMap</tt> as in:</p>
+ <p>There are two ways to select a different charmap with
+ FreeType 2. The easiest is if the encoding you need already has
+ a corresponding enumeration defined in
+ <tt><freetype/freetype.h></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>
+ 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>Another way is to manually parse the list of charmaps for the face,
+ this is accessible through the fields <tt>num_charmaps</tt> and
+ <tt>charmaps</tt> (notice the final '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>
+ precisely. Mainly, one will look at <tt>charmap->platform_id</tt> and
+ <tt>charmap->encoding_id</tt> which 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><freetype/ftnameid.h></tt> which defines several
- helpful constants to deal with them..</p>
+ <p>Each value pair corresponds to a given encoding. For example, the
+ pair (3,1) corresponds to Unicode. A list of such pairs is defined in
+ the TrueType specification, but you can also use the file
+ <tt><freetype/ftnameid.h></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>
+ <p>To look up a specific encoding you need to find a corresponding
+ value pair in the specification, then look for it in the charmaps
+ list. Bear in mind that some encodings correspond to several values
+ pairs (yes, it's a real mess, but blame Apple and Microsoft on such
+ stupidity). Here some code to do it:</p>
<font color="blue">
<pre>
@@ -620,6 +612,7 @@
FT_CharMap charmap;
int n;
+
for ( n = 0; n < face->num_charmaps; n++ )
{charmap = face->charmaps[n];
@@ -638,315 +631,317 @@
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>
+ <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:
+ d. Glyph transformations
</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>It is possible to specify an affine transformation to be applied to
+ glyph images when they are 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>
+ <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 */
- &matrix, /* pointer to 2x2 matrix */
- &delta ); /* pointer to 2d vector */
- </pre></font>
+ <font color="blue">
+ <pre>
+ error = FT_Set_Transform(
+ face, /* target face object */
+ &matrix, /* pointer to 2x2 matrix */
+ &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>This function will set the current transformation for a given face
+ object. Its second parameter is a pointer to a <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 describes a simple 2d
+ vector that is used to translate the glyph image <em>after</em> the
+ 2x2 transformation.</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>Note that the matrix pointer can be set to NULL, in which case the
+ identity transformation 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>The vector pointer can also be set to NULL in which case a delta
+ vector 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>
- <font color="red">
- <p>NOTA BENE: The transform is applied to every glyph that is loaded
- through <tt>FT_Load_Glyph</tt> and is <b>completely independent
- of any hinting process.</b> This means that you won't get the same
- results if you load a glyph at the size of 24 pixels, or a glyph at
- the size at 12 pixels scaled by 2 through a transform, because the
- hints will have been computed differently (unless, of course you
- disabled hints).</em></p></font>
+ <p><em>The transformation is applied to every glyph that is loaded
+ through <tt>FT_Load_Glyph()</tt> and is <b>completely independent of
+ any hinting process.</b> This means that you won't get the same
+ results if you load a glyph at the size of 24 pixels, or a glyph
+ at the size at 12 pixels scaled by 2 through a
+ transformation, because the hints will have been computed differently
+ (unless hints have been disabled, of course).</em></p>
- <p>If you ever need to use a non-orthogonal transform with optimal
- hints, you first need to decompose your transform into a scaling part
- and a rotation/shearing part. Use the scaling part to compute a new
- character pixel size, then the other one to call FT_Set_Transform.
- This is explained in details in a later section of this tutorial.</p>
+ <p>If you ever need to use a non-orthogonal transformation with
+ optimal hints, you first need to decompose your transformation into a
+ scaling part and a rotation/shearing part. Use the scaling part to
+ compute a new character pixel size, then the other one to call
+ <tt>FT_Set_Transform()</tt>. This is explained in details in a later
+ section of this tutorial.</p>
- <p>Note also that loading a glyph bitmap with a non-identity transform
- will produce an error..</p>
- <hr>
+ <p>Note also that loading a glyph bitmap with a non-identity
+ transformation will produce an error.</p>
+ <hr>
+
<h3>
- 7. Simple Text Rendering:
+ 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>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>
+ 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>
+ <h4>
+ a. basic code
+ </h4>
- <p>The following code performs our simple text rendering with the
- functions previously described.</p>
+ <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;
+ <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 ..
+
+ .. initialize library ..
+ .. create face object ..
+ .. set character size ..
- pen_x = 300;
- pen_y = 200;
+ pen_x = 300;
+ pen_y = 200;
- for ( n = 0; n < num_chars; n++ )
- {- FT_UInt glyph_index;
+ for ( n = 0; n < num_chars; n++ )
+ {+ FT_UInt glyph_index;
- // retrieve glyph index from character code
- glyph_index = FT_Get_Char_Index( face, text[n] );
+
+ /* 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
+ /* 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_normal );
- if (error) continue;
+ /* convert to an anti-aliased bitmap */
+ error = FT_Render_Glyph( face->glyph, ft_render_mode_normal );
+ if ( error ) continue;
- // now, draw to our target surface
- my_draw_bitmap( &slot->bitmap,
- pen_x + slot->bitmap_left,
- pen_y - slot->bitmap_top );
+ /* 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>
+ /* increment pen position */
+ pen_x += slot->advance.x >> 6;
+ pen_y += slot->advance.y >> 6; /* not useful 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>
+ <p>This code needs a few explanations:</p>
+
+ <ul>
+ <li>
+ 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.) This is a convenience to avoid using
+ <tt>face->glyph->XXX</tt> every time.
+ </li>
+ <li>
+ We increment the pen position with the vector
+ <tt>slot->advance</tt>, which corresponds to the glyph's
+ <em>advance width</em> (also known as its <em>escapement</em>).
+ The advance vector is expressed in 1/64th of pixels, and is
+ truncated to integer pixels on each iteration.
+ </li>
+ <li>
+ 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
+ <tt>FT_Bitmap</tt> descriptor and the position of its top-left
+ corner as arguments.
+ </li>
+ <li>
+ 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.
+ </li>
+ </ul>
- <h4>b. refined code:</h4>
+ <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>
+ <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 which will 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;
+ <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 ..
+
+ .. initialize library ..
+ .. create face object ..
+ .. set character size ..
- pen_x = 300;
- pen_y = 200;
+ pen_x = 300;
+ pen_y = 200;
- for ( n = 0; n < num_chars; n++ )
- {- // load glyph image into the slot (erase previous one)
- error = FT_Load_Char( face, text[n], FT_LOAD_RENDER );
- if (error) continue; // ignore errors
+ for ( n = 0; n < num_chars; n++ )
+ {+ /* load glyph image into the slot (erase previous one) */
+ error = FT_Load_Char( face, text[n], FT_LOAD_RENDER );
+ 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 );
+ /* 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>
+ /* 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>
+ <p>We have reduced the size of our code, but it does exactly the same
+ thing.</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 bit flag <tt><b>FT_LOAD_RENDER</b></tt>. It indicates that
- the glyph image must be immediately converted to an anti-aliased
- bitmap. This is of course a shortcut that avoids calling
- <tt>FT_Render_Glyph</tt> explicitely but is strictly equivalent.</p>
+ <ul>
+ <li>
+ <p>We use the function <tt>FT_Load_Char()</tt> instead of
+ <tt>FT_Load_Glyph()</tt>. As you probably imagine, it is
+ equivalent to calling <tt>FT_Get_Char_Index()</tt> followed by
+ <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 bit flag <tt>FT_LOAD_RENDER</tt>. It indicates that the glyph
+ image must be immediately converted to an anti-aliased bitmap.
+ This is of course a shortcut that avoids calling
+ <tt>FT_Render_Glyph()</tt> explicitly but is strictly
+ equivalent.</p>
- <p>
- Note that you can also specify that you want a monochrome bitmap
- instead by using the addition <tt><b>FT_LOAD_MONOCHROME</b></tt>
- load flag.
- </p></li>
- </ul>
+ <p>Note that you can also specify that you want a monochrome
+ bitmap instead by using the additional <tt>FT_LOAD_MONOCHROME</tt>
+ load flag.</p>
+ </li>
+ </ul>
- <h4>c. more advanced rendering:</h4>
+ <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>
+ <p>We now render transformed text (for example through a rotation).
+ To do that we use <tt>FT_Set_Transform()</tt>:</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;
+ <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);
+ .. initialize library ..
+ .. create face object ..
+ .. set character size ..
+
+ /* set up matrix */
+ matrix.xx = (FT_Fixed)( cos( angle ) * 0x10000L );
+ matrix.xy = (FT_Fixed)(-sin( angle ) * 0x10000L );
+ matrix.yx = (FT_Fixed)( sin( angle ) * 0x10000L );
+ matrix.yy = (FT_Fixed)( cos( angle ) * 0x10000L );
- // the pen position in 26.6 cartesian space coordinates
- pen.x = 300 * 64;
- pen.y = ( my_target_height - 200 ) * 64;
+ /* the pen position in 26.6 cartesian space coordinates */
+ pen.x = 300 * 64;
+ pen.y = ( my_target_height - 200 ) * 64;
- for ( n = 0; n < num_chars; n++ )
- {- // set transform
- FT_Set_Transform( face, &matrix, &pen );
+ for ( n = 0; n < num_chars; n++ )
+ {+ /* set transformation */
+ 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 );
- if (error) continue; // ignore errors
+ /* load glyph image into the slot (erase previous one) */
+ error = FT_Load_Char( face, text[n], FT_LOAD_RENDER );
+ 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 );
+ /* 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>
+ /* increment pen position */
+ pen.x += slot->advance.x;
+ pen.y += slot->advance.y;
+ }</pre>
+ </font>
- <p>You'll notice that:</p>
+ <p>Notes:</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
+ <ul>
+ <li>
+ 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.
+ </li>
+ <li>
+ 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
+ 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>
+ </li>
+ <li>
+ We set the transformation on each glyph to indicate the rotation
+ matrix, as well as a delta vector that will move the transformed
+ image to the current pen position (in cartesian space, not bitmap
+ space).
+ </li>
+ <li>
+ The advance width is always returned transformed, which is why it
+ can be directly added to the current pen position. Note that it
+ is <em>not</em> rounded this time.
+ </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>
+ <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 transformation is the identity. Hence it can be used as a
+ replacement (but a more powerful one).</p>
- <p>It has however a few short comings that we will explain, and solve,
- in the next part of this tutorial.</p>
+ <p>It has, however, a few shortcomings that we will explain, and
+ solve, in the next part of this tutorial.</p>
<hr>
<h3>
- Conclusion
+ 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>In this first section, you have learned the basics of
+ FreeType 2, as well as sufficient knowledge how to render rotated
+ text.</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 next part 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>
+ <p>The third part 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>