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8 <title>FreeType 2 Tutorial</title>
18 FreeType 2.0 Tutorial<br>
19 Step 1 - simple glyph loading
23 © 2000 David Turner
24 (<a href="mailto:david@freetype.org">david@freetype.org</a>)<br>
25 © 2000 The FreeType Development Team
26 (<a href="http://www.freetype.org">www.freetype.org</a>)
39 <p>This is the first section of the FreeType 2 tutorial. It will teach
40 you to do the following:</p>
43 <li>initialise the library</li>
44 <li>open a font file by creating a new face object</li>
45 <li>select a character size in points or in pixels</li>
46 <li>load a single glyph image and convert it to a bitmap</li>
47 <li>render a very simple string of text</li>
48 <li>render a rotated string of text easily</li>
57 <p>To include the main FreeType header file, simply say</p>
61 #include <freetype/freetype.h></pre>
64 <p>in your application code. Note that other files are available in the
65 FreeType include directory, most of them being included by
66 <tt>"freetype.h"</tt>. They will be described later in this
72 2. Initialize the library
75 <p>Simply create a variable of type <tt>FT_Library</tt> named, for
76 example, <tt>library</tt>, and call the function
77 <tt>FT_Init_FreeType()</tt> as in</p>
81 #include <freetype/freetype.h>
89 error = FT_Init_FreeType( &library );
92 ... an error occurred during library initialization ...
97 <p>This function is in charge of the following:</p>
101 <p>Creating a new instance of the FreeType 2 library, and set
102 the handle <tt>library</tt> to it.</p>
105 <p>Load each modules that FreeType knows about in the library.
106 This means that by default, your new <tt>library</tt> object is able
107 to handle TrueType, Type 1, CID-keyed & OpenType/CFF fonts
112 <p>As you can see, the function returns an error code, like most others
113 in the FreeType API. An error code of 0 <em>always</em> means that
114 the operation was successful; otherwise, the value describes the error,
115 and <tt>library</tt> is set to NULL.</p>
127 <p>Create a new <em>face</em> object by calling <tt>FT_New_Face</tt>.
128 A <em>face</em> describes a given typeface and style. For example,
129 "Times New Roman Regular" and "Times New Roman Italic" correspond to
130 two different faces.</p>
134 FT_Library library; /* handle to library */
135 FT_Face face; /* handle to face object */
137 error = FT_Init_FreeType( &library );
140 error = FT_New_Face( library,
141 "/usr/share/fonts/truetype/arial.ttf",
144 if ( error == FT_Err_Unknown_File_Format )
146 ... the font file could be opened and read, but it appears
147 ... that its font format is unsupported
151 ... another error code means that the font file could not
152 ... be opened or read, or simply that it is broken...
156 <p>As you can certainly imagine, <tt>FT_New_Face</tt> opens a font
157 file, then tries to extract one face from it. Its parameters are</p>
159 <table cellpadding=5>
162 <tt><b>library</b></tt>
165 <p>handle to the FreeType library instance where the face object
171 <tt><b>filepathname</b></tt>
174 <p>the font file pathname (standard C string).</p>
179 <tt><b>face_index</b></tt>
182 <p>Certain font formats allow several font faces to be embedded
183 in a single file.</p>
185 <p>This index tells which face you want to load. An error will
186 be returned if its value is too large.</p>
188 <p>Index 0 always work though.</p>
196 <p>A <em>pointer</em> to the handle that will be set to describe
197 the new face object.</p>
199 <p>It is set to NULL in case of error.</p>
204 <p>To know how many faces a given font file contains, simply load its
205 first face (use <tt>face_index</tt>=0), then see the value of
206 <tt>face->num_faces</tt> which indicates how many faces are embedded
207 in the font file.</p>
213 <p>In the case where you have already loaded the font file in memory,
214 you can similarly create a new face object for it by calling
215 <tt>FT_New_Memory_Face</tt> as in</p>
219 FT_Library library; /* handle to library */
220 FT_Face face; /* handle to face object */
222 error = FT_Init_FreeType( &library );
225 error = FT_New_Memory_Face( library,
226 buffer, /* first byte in memory */
227 size, /* size in bytes */
230 if ( error ) { ... }</pre>
233 <p>As you can see, <tt>FT_New_Memory_Face()</tt> simply takes a
234 pointer to the font file buffer and its size in bytes instead of a
235 file pathname. Other than that, it has exactly the same semantics as
236 <tt>FT_New_Face()</tt>.</p>
239 c. From other sources (compressed files, network, etc.)
242 <p>There are cases where using a file pathname or preloading the file
243 in memory is simply not enough. With FreeType 2, it is possible
244 to provide your own implementation of i/o routines.</p>
246 <p>This is done through the <tt>FT_Open_Face()</tt> function, which
247 can be used to open a new font face with a custom input stream, select
248 a specific driver for opening, or even pass extra parameters to the
249 font driver when creating the object. We advise you to refer to the
250 FreeType 2 reference manual in order to learn how to use it.</p>
252 <p>Note that providing a custom stream might also be used to access a
253 TrueType font embedded in a Postscript Type 42 wrapper.</p>
258 4. Accessing face content
261 <p>A <em>face object</em> models all information that globally describes
262 the face. Usually, this data can be accessed directly by dereferencing
265 <table cellpadding=5>
268 <tt><b>face->num_glyphs</b></tt>
271 <p>Gives the number of <em>glyphs</em> available in the font face.
272 A glyph is simply a character image. It doesn't necessarily
273 correspond to a <em>character code</em> though.</p>
278 <tt><b>face->flags</b></tt>
281 <p>A 32-bit integer containing bit flags used to describe some
282 face properties. For example, the flag
283 <tt>FT_FACE_FLAG_SCALABLE</tt> is used to indicate that the face's
284 font format is scalable and that glyph images can be rendered for
285 all character pixel sizes. For more information on face flags,
286 please read the <a href="#">FreeType 2 API Reference</a>.</p>
291 <tt><b>face->units_per_EM</b></tt>
294 <p>This field is only valid for scalable formats (it is set to 0
295 otherwise). It indicates the number of font units covered by the
301 <tt><b>face->num_fixed_sizes</b></tt>
304 <p>This field gives the number of embedded bitmap <em>strikes</em>
305 in the current face. A <em>strike</em> is simply a series of
306 glyph images for a given character pixel size. For example, a
307 font face could include strikes for pixel sizes 10, 12
308 and 14. Note that even scalable font formats can have
309 embedded bitmap strikes!</p>
314 <tt><b>face->fixed_sizes</b></tt>
317 <p>this is a pointer to an array of <tt>FT_Bitmap_Size</tt>
318 elements. Each <tt>FT_Bitmap_Size</tt> indicates the horizontal
319 and vertical <em>pixel sizes</em> for each of the strikes that are
320 present in the face.</p>
325 <p>For a complete listing of all face properties and fields, please read
326 the <a href="#">FreeType 2 API Reference</a>.<p>
331 5. Setting the current pixel size
334 <p>FreeType 2 uses "<em>size objects</em>" to model all
335 information related to a given character size for a given face.
336 For example, a size object will hold the value of certain metrics
337 like the ascender or text height, expressed in 1/64th of a pixel,
338 for a character size of 12 points.</p>
340 <p>When the <tt>FT_New_Face</tt> function is called (or one of its
341 cousins), it <b>automatically</b> creates a new size object for
342 the returned face. This size object is directly accessible as
343 <b><tt>face->size</tt></b>.</p>
345 <p><em>NOTA BENE: a single face object can deal with one or more size
346 objects at a time, however, this is something that few programmers
347 really need to do. We have thus have decided to simplify the API for
348 the most common use (i.e. one size per face), while keeping this
349 feature available through additional fuctions.</em></p>
351 <p>When a new face object is created, its size object defaults to the
352 character size of 10 pixels (both horizontally and vertically) for
353 scalable formats. For fixed-sizes formats, the size is more or less
354 undefined, which is why you must set it before trying to load a
357 <p>To do that, simply call <tt>FT_Set_Char_Size()</tt>. Here is an
358 example where the character size is set to 16pt for a 300x300 dpi
363 error = FT_Set_Char_Size(
364 face, /* handle to face object */
365 0, /* char_width in 1/64th of points */
366 16*64, /* char_height in 1/64th of points */
367 300, /* horizontal device resolution */
368 300 ); /* vertical device resolution */</pre>
371 <p>You will notice that:</p>
375 <p>The character width and heights are specified in 1/64th of
376 points. A point is a <em>physical</em> distance, equaling 1/72th
377 of an inch, it's not a pixel..<p>
380 <p>The horizontal and vertical device resolutions are expressed in
381 <em>dots-per-inch</em>, or <em>dpi</em>. You can use 72 or
382 96 dpi for display devices like the screen. The resolution
383 is used to compute the character pixel size from the character
387 <p>A value of 0 for the character width means "<em>same as
388 character height</em>", a value of 0 for the character height
389 means "<em>same as character width</em>". Otherwise, it is possible
390 to specify different char widths and heights.</p>
393 <p>Using a value of 0 for the horizontal or vertical resolution means
394 72 dpi, which is the default.</p>
397 <p>The first argument is a handle to a face object, not a size
398 object. That's normal, and must be seen as a convenience.</p>
402 <p>This function computes the character pixel size that corresponds to
403 the character width and height and device resolutions. However, if you
404 want to specify the pixel sizes yourself, you can simply call
405 <tt>FT_Set_Pixel_Sizes()</tt>, as in</p>
409 error = FT_Set_Pixel_Sizes(
410 face, /* handle to face object */
412 16 ); /* pixel_height */</pre>
415 <p>This example will set the character pixel sizes to 16x16 pixels.
416 As previously, a value of 0 for one of the dimensions means
417 "<em>same as the other</em>".</p>
419 <p>Note that both functions return an error code. Usually, an error
420 occurs with a fixed-size font format (like FNT or PCF) when trying to
421 set the pixel size to a value that is not listed in the
422 <tt><b>face->fixed_sizes</b></tt> array.</p>
427 6. Loading a glyph image
431 a. Converting a character code into a glyph index
434 <p>Usually, an application wants to load a glyph image based on its
435 <em>character code</em>, which is a unique value that defines the
436 character for a given <em>encoding</em>. For example, the character
437 code 65 represents the `A' in ASCII encoding.</p>
439 <p>A face object contains one or more tables, called
440 <em>charmaps</em>, that are used to convert character codes to glyph
441 indices. For example, most TrueType fonts contain two charmaps. One
442 is used to convert Unicode character codes to glyph indices, the other
443 is used to convert Apple Roman encoding into glyph indices. Such
444 fonts can then be used either on Windows (which uses Unicode) and
445 Macintosh (which uses Apple Roman, bwerk). Note also that a given
446 charmap might not map to all the glyphs present in the font.</p>
448 <p>By default, when a new face object is created, it lists all the
449 charmaps contained in the font face and selects the one that supports
450 Unicode character codes if it finds one. Otherwise, it tries to find
451 support for Latin-1, then ASCII.</p>
453 <p>We will describe later how to look for specific charmaps in a face.
454 For now, we will assume that the face contains at least a Unicode
455 charmap that was selected during <tt>FT_New_Face()</tt>. To convert a
456 Unicode character code to a font glyph index, we use
457 <tt>FT_Get_Char_Index()</tt> as in</p>
461 glyph_index = FT_Get_Char_Index( face, charcode );</pre>
464 <p>This will look the glyph index corresponding to the given
465 <tt>charcode</tt> in the charmap that is currently selected for the
466 face. If charmap is selected, the function simply returns the
469 <p>Note that this is one of the rare FreeType functions that do not
470 return an error code. However, when a given character code has no
471 glyph image in the face, the value 0 is returned. By convention,
472 it always correspond to a special glyph image called the <b>missing
473 glyph</b>, which usually is represented as a box or a space.</p>
476 b. Loading a glyph from the face
479 <p>Once you have a glyph index, you can load the corresponding glyph
480 image. The latter can be stored in various formats within the font file.
481 For fixed-size formats like FNT or PCF, each image is a bitmap. Scalable
482 formats like TrueType or Type 1 use vectorial shapes, named "outlines"
483 to describe each glyph. Some formats may have even more exotic ways
484 of representing glyph (e.g. MetaFont). Fortunately, FreeType 2 is
485 flexible enough to support any kind of glyph format through
488 <p>The glyph image is always stored in a special object called a
489 <em>glyph slot</em>. As its name suggests, a glyph slot is simply a
490 container that is able to hold one glyph image at a time, be it a
491 bitmap, an outline, or something else. Each face object has a single
492 glyph slot object that can be accessed as
493 <b><tt>face->glyph</tt></b>.</p>
495 <p>Loading a glyph image into the slot is performed by calling
496 <tt>FT_Load_Glyph()</tt> as in</p>
500 error = FT_Load_Glyph(
501 face, /* handle to face object */
502 glyph_index, /* glyph index */
503 load_flags ); /* load flags, see below */</pre>
506 <p>The <tt>load_flags</tt> value is a set of bit flags used to
507 indicate some special operations. The default value
508 <tt>FT_LOAD_DEFAULT</tt> is 0.</p>
510 <p>This function will try to load the corresponding glyph image
511 from the face. Basically, this means that:</p>
515 <p>If a bitmap is found for the corresponding glyph and pixel
516 size, it will be loaded into the slot (embedded bitmaps are always
517 favored over native image formats, because we assume that
518 they are higher-quality versions of the same glyph. This
519 can be ignored by using the FT_LOAD_NO_BITMAP flag)</p>
523 <p>Otherwise, a native image for the glyph will be loaded.
524 It will also be scaled to the current pixel size, as
525 well as hinted for certain formats like TrueType and
530 <p>The field <tt><b>glyph->format</b></tt> describe the format
531 used to store the glyph image in the slot. If it is not
532 <tt>ft_glyph_format_bitmap</tt>, one can immediately
533 convert it to a bitmap through <tt>FT_Render_Glyph</tt>,
538 error = FT_Render_Glyph(
539 face->glyph, /* glyph slot */
540 render_mode ); /* render mode */
544 <p>The parameter <tt>render_mode</tt> is a set of bit flags used
545 to specify how to render the glyph image. Set it to 0, or the
546 equivalent <tt>ft_render_mode_normal</tt> to render a high-quality
547 anti-aliased (256 gray levels) bitmap, as this is the default.
548 You can alternatively use <tt>ft_render_mode_mono</tt> if you
549 want to generate a 1-bit monochrome bitmap.</p>
551 <p>Once you have a bitmapped glyph image, you can access it directly
552 through <tt><b>glyph->bitmap</b></tt> (a simple bitmap descriptor),
553 and position it through <tt><b>glyph->bitmap_left</b></tt> and
554 <tt><b>glyph->bitmap_top</b></tt>.</p>
556 <p>Note that <tt>bitmap_left</tt> is the horizontal distance from the
557 current pen position to the left-most border of the glyph bitmap,
558 while <tt>bitmap_top</tt> is the vertical distance from the
559 pen position (on the baseline) to the top-most border of the
560 glyph bitmap. <em>It is positive to indicate an upwards
563 <p>The next section will detail the content of a glyph slot and
564 how to access specific glyph information (including metrics).</p>
567 c. Using other charmaps
570 <p>As said before, when a new face object is created, it will look for
571 a Unicode, Latin-1, or ASCII charmap and select it. The currently
572 selected charmap is accessed via <b><tt>face->charmap</tt></b>. This
573 field is NULL when no charmap is selected, which typically happens
574 when you create a new <tt>FT_Face</tt> object from a font file that
575 doesn't contain an ASCII, Latin-1, or Unicode charmap (rare
578 <p>There are two ways to select a different charmap with FreeType 2.
579 The easiest is when the encoding you need already has a corresponding
580 enumeration defined in <tt><freetype/freetype.h></tt>, as
581 <tt>ft_encoding_big5</tt>. In this case, you can simply call
582 <tt>FT_Select_CharMap</tt> as in:</p>
584 <font color="blue"><pre>
585 error = FT_Select_CharMap(
586 face, /* target face object */
587 ft_encoding_big5 ); /* encoding.. */
590 <p>Another way is to manually parse the list of charmaps for the
591 face, this is accessible through the fields
592 <tt><b>num_charmaps</b></tt> and <tt><b>charmaps</b></tt>
593 (notice the 's') of the face object. As you could expect,
594 the first is the number of charmaps in the face, while the
595 second is <em>a table of pointers to the charmaps</em>
596 embedded in the face.</p>
598 <p>Each charmap has a few visible fields used to describe it more
599 precisely. Mainly, one will look at
600 <tt><b>charmap->platform_id</b></tt> and
601 <tt><b>charmap->encoding_id</b></tt> that define a pair of
602 values that can be used to describe the charmap in a rather
605 <p>Each value pair corresponds to a given encoding. For example,
606 the pair (3,1) corresponds to Unicode. Their list is
607 defined in the TrueType specification but you can also use the
608 file <tt><freetype/ftnameid.h></tt> which defines several
609 helpful constants to deal with them..</p>
611 <p>To look for a specific encoding, you need to find a corresponding
612 value pair in the specification, then look for it in the charmaps
613 list. Don't forget that some encoding correspond to several
614 values pair (yes it's a real mess, but blame Apple and Microsoft
615 on such stupidity..). Here's some code to do it:</p>
619 FT_CharMap found = 0;
623 for ( n = 0; n < face->num_charmaps; n++ )
625 charmap = face->charmaps[n];
626 if ( charmap->platform_id == my_platform_id &&
627 charmap->encoding_id == my_encoding_id )
634 if ( !found ) { ... }
636 /* now, select the charmap for the face object */
637 error = FT_Set_CharMap( face, found );
638 if ( error ) { ... }</pre>
641 <p>Once a charmap has been selected, either through
642 <tt>FT_Select_CharMap</tt> or <tt>FT_Set_CharMap</tt>,
643 it is used by all subsequent calls to
644 <tt>FT_Get_Char_Index()</tt>.</p>
651 <p>It is possible to specify an affine transformation to be applied
652 to glyph images when they're loaded. Of course, this will only
653 work for scalable (vectorial) font formats.</p>
655 <p>To do that, simply call <tt>FT_Set_Transform</tt>, as in:</p>
657 <font color="blue"><pre>
658 error = FT_Set_Transform(
659 face, /* target face object */
660 &matrix, /* pointer to 2x2 matrix */
661 &delta ); /* pointer to 2d vector */
664 <p>This function will set the current transform for a given face
665 object. Its second parameter is a pointer to a simple
666 <tt>FT_Matrix</tt> structure that describes a 2x2 affine matrix.
667 The third parameter is a pointer to a <tt>FT_Vector</tt> structure
668 that describe a simple 2d vector that is used to translate the
669 glyph image <em>after</em> the 2x2 transform.</p>
671 <p>Note that the matrix pointer can be set to NULL, (in which case
672 the identity transform will be used). Coefficients of the matrix
673 are otherwise in 16.16 fixed float units.</p>
675 <p>The vector pointer can also be set to NULL (in which case a delta
676 of (0,0) will be used). The vector coordinates are expressed in
677 1/64th of a pixel (also known as 26.6 fixed floats).</p>
680 <p>NOTA BENE: The transform is applied to every glyph that is loaded
681 through <tt>FT_Load_Glyph</tt> and is <b>completely independent
682 of any hinting process.</b> This means that you won't get the same
683 results if you load a glyph at the size of 24 pixels, or a glyph at
684 the size at 12 pixels scaled by 2 through a transform, because the
685 hints will have been computed differently (unless, of course you
686 disabled hints).</em></p></font>
688 <p>If you ever need to use a non-orthogonal transform with optimal
689 hints, you first need to decompose your transform into a scaling part
690 and a rotation/shearing part. Use the scaling part to compute a new
691 character pixel size, then the other one to call FT_Set_Transform.
692 This is explained in details in a later section of this tutorial.</p>
694 <p>Note also that loading a glyph bitmap with a non-identity transform
695 will produce an error..</p>
699 7. Simple Text Rendering:
702 <p>We will now present you with a very simple example used to render
703 a string of 8-bit Latin-1 text, assuming a face that contains a
706 <p>The idea is to create a loop that will, on each iteration, load one
707 glyph image, convert it to an anti-aliased bitmap, draw it on the
708 target surface, then increment the current pen position</p>
710 <h4>a. basic code :</h4>
712 <p>The following code performs our simple text rendering with the
713 functions previously described.</p>
715 <font color="blue"><pre>
716 FT_GlyphSlot slot = face->glyph; // a small shortcut
719 .. initialise library ..
720 .. create face object ..
721 .. set character size ..
726 for ( n = 0; n < num_chars; n++ )
730 // retrieve glyph index from character code
731 glyph_index = FT_Get_Char_Index( face, text[n] );
733 // load glyph image into the slot (erase previous one)
734 error = FT_Load_Glyph( face, glyph_index, FT_LOAD_DEFAULT );
735 if (error) continue; // ignore errors
737 // convert to an anti-aliased bitmap
738 error = FT_Render_Glyph( face->glyph, ft_render_mode_normal );
741 // now, draw to our target surface
742 my_draw_bitmap( &slot->bitmap,
743 pen_x + slot->bitmap_left,
744 pen_y - slot->bitmap_top );
746 // increment pen position
747 pen_x += slot->advance.x >> 6;
748 pen_y += slot->advance.y >> 6; // unuseful for now..
752 <p>This code needs a few explanations:</p>
755 we define a handle named <tt>slot</tt> that points to the
756 face object's glyph slot. (the type <tt>FT_GlyphSlot</tt> is
757 a pointer). That's a convenience to avoid using
758 <tt>face->glyph->XXX</tt> every time.
762 we increment the pen position with the vector <tt>slot->advance</tt>,
763 which correspond to the glyph's <em>advance width</em> (also known
764 as its <em>escapement</em>). The advance vector is expressed in
765 64/th of pixels, and is truncated to integer pixels on each
770 The function <tt>my_draw_bitmap</tt> is not part of FreeType, but
771 must be provided by the application to draw the bitmap to the target
772 surface. In this example, it takes a pointer to a FT_Bitmap descriptor
773 and the position of its top-left corner as arguments.
777 The value of <tt>slot->bitmap_top</tt> is positive for an
778 <em>upwards</em> vertical distance. Assuming that the coordinates
779 taken by <tt>my_draw_bitmap</tt> use the opposite convention
780 (increasing Y corresponds to downwards scanlines), we substract
781 it to <tt>pen_y</tt>, instead of adding it..
786 <h4>b. refined code:</h4>
788 <p>The following code is a refined version of the example above. It
789 uses features and functions of FreeType 2 that have not yet been
790 introduced, and they'll be explained below:</p>
792 <font color="blue"><pre>
793 FT_GlyphSlot slot = face->glyph; // a small shortcut
797 .. initialise library ..
798 .. create face object ..
799 .. set character size ..
804 for ( n = 0; n < num_chars; n++ )
806 // load glyph image into the slot (erase previous one)
807 error = FT_Load_Char( face, text[n], FT_LOAD_RENDER );
808 if (error) continue; // ignore errors
810 // now, draw to our target surface
811 my_draw_bitmap( &slot->bitmap,
812 pen_x + slot->bitmap_left,
813 pen_y - slot->bitmap_top );
815 // increment pen position
816 pen_x += slot->advance.x >> 6;
820 <p>We've reduced the size of our code, but it does exactly the same thing,
825 We use the function <tt><b>FT_Load_Char</b></tt> instead of
826 <tt>FT_Load_Glyph</tt>. As you probably imagine, it's equivalent
827 to calling <tt>FT_Get_Char_Index</tt> then <tt>FT_Get_Load_Glyph</tt>.
831 We do not use <tt>FT_LOAD_DEFAULT</tt> for the loading mode, but
832 the bit flag <tt><b>FT_LOAD_RENDER</b></tt>. It indicates that
833 the glyph image must be immediately converted to an anti-aliased
834 bitmap. This is of course a shortcut that avoids calling
835 <tt>FT_Render_Glyph</tt> explicitely but is strictly equivalent.</p>
838 Note that you can also specify that you want a monochrome bitmap
839 instead by using the addition <tt><b>FT_LOAD_MONOCHROME</b></tt>
844 <h4>c. more advanced rendering:</h4>
846 <p>Let's try to render transformed text now (for example through a
847 rotation). We can do this using <tt>FT_Set_Transform</tt>. Here's
850 <font color="blue"><pre>
851 FT_GlyphSlot slot = face->glyph; // a small shortcut
852 FT_Matrix matrix; // transformation matrix
854 FT_Vector pen; // untransformed origin
857 .. initialise library ..
858 .. create face object ..
859 .. set character size ..
862 matrix.xx = (FT_Fixed)( cos(angle)*0x10000);
863 matrix.xy = (FT_Fixed)(-sin(angle)*0x10000);
864 matrix.yx = (FT_Fixed)( sin(angle)*0x10000);
865 matrix.yy = (FT_Fixed)( cos(angle)*0x10000);
867 // the pen position in 26.6 cartesian space coordinates
869 pen.y = ( my_target_height - 200 ) * 64;
871 for ( n = 0; n < num_chars; n++ )
874 FT_Set_Transform( face, &matrix, &pen );
876 // load glyph image into the slot (erase previous one)
877 error = FT_Load_Char( face, text[n], FT_LOAD_RENDER );
878 if (error) continue; // ignore errors
880 // now, draw to our target surface (convert position)
881 my_draw_bitmap( &slot->bitmap,
883 my_target_height - slot->bitmap_top );
885 // increment pen position
886 pen.x += slot->advance.x;
887 pen.y += slot->advance.y;
891 <p>You'll notice that:</p>
895 we now use a vector, of type <tt>FT_Vector</tt> to store the pen
896 position, with coordinates expressed as 1/64th of pixels, hence
897 a multiplication. The position is expressed in cartesian space.
901 glyph images are always loaded, transformed and described in the
902 cartesian coordinate system in FreeType (which means that
903 increasing Y corresponds to upper scanlines), unlike the system
904 typically used for bitmaps (where the top-most scanline has
905 coordinate 0). We must thus convert between the two systems
906 when we define the pen position, and when we compute the top-left
907 position of the bitmap.
911 we set the transform on each glyph, to indicate the rotation
912 matrix, as well as a delta that will move the transformed image
913 to the current pen position (in cartesian space, not bitmap space).
917 the advance is always returned transformed, which is why it can
918 be directly added to the current pen position. Note that it is
919 <b>not</b> rounded this time.
924 <p>It is important to note that, while this example is a bit more
925 complex than the previous one, it is strictly equivalent
926 for the case where the transform is the identity.. Hence it can
927 be used as a replacement (but a more powerful one).</p>
929 <p>It has however a few short comings that we will explain, and solve,
930 in the next part of this tutorial.</p>
938 <p>In this first section, you have learned the basics of FreeType 2,
939 as well as sufficient knowledge to know how to render rotated text.
940 Woww ! Congratulations..</p>
942 <p>The next section will dive into more details of the API in order
943 to let you access glyph metrics and images directly, as well as
944 how to deal with scaling, hinting, kerning, etc..</p>
946 <p>The third section will discuss issues like modules, caching and a
947 few other advanced topics like how to use multiple size objects