typedef struct  FT_Outline_
  {
    short       n_contours;      /* number of contours in glyph        */
    short       n_points;        /* number of points in the glyph      */

    FT_Vector*  points;          /* the outline's points               */
    char*       tags;            /* the points flags                   */
    short*      contours;        /* the contour end points             */

    int         flags;           /* outline masks                      */

  } FT_Outline;

  /* Following limits must be consistent with */
  /* FT_Outline.{n_contours,n_points}         */
#define FT_OUTLINE_CONTOURS_MAX  SHRT_MAX
#define FT_OUTLINE_POINTS_MAX    SHRT_MAX

This structure is used to describe an outline to the scan-line converter.

The B/W rasterizer only checks bit 2 in the ‘tags’ array for the first point of each contour. The drop-out mode as given with FT_OUTLINE_IGNORE_DROPOUTS, FT_OUTLINE_SMART_DROPOUTS, and FT_OUTLINE_INCLUDE_STUBS in ‘flags’ is then overridden.

#define FT_OUTLINE_NONE             0x0
#define FT_OUTLINE_OWNER            0x1
#define FT_OUTLINE_EVEN_ODD_FILL    0x2
#define FT_OUTLINE_REVERSE_FILL     0x4
#define FT_OUTLINE_IGNORE_DROPOUTS  0x8
#define FT_OUTLINE_SMART_DROPOUTS   0x10
#define FT_OUTLINE_INCLUDE_STUBS    0x20

#define FT_OUTLINE_HIGH_PRECISION   0x100
#define FT_OUTLINE_SINGLE_PASS      0x200

A list of bit-field constants use for the flags in an outline's ‘flags’ field.

The flags FT_OUTLINE_IGNORE_DROPOUTS, FT_OUTLINE_SMART_DROPOUTS, and FT_OUTLINE_INCLUDE_STUBS are ignored by the smooth rasterizer.

There exists a second mechanism to pass the drop-out mode to the B/W rasterizer; see the ‘tags’ field in FT_Outline.

Please refer to the description of the ‘SCANTYPE’ instruction in the OpenType specification (in file ‘ttinst1.doc’) how simple drop-outs, smart drop-outs, and stubs are defined.

  FT_EXPORT( FT_Error )
  FT_Outline_New( FT_Library   library,
                  FT_UInt      numPoints,
                  FT_Int       numContours,
                  FT_Outline  *anoutline );


  FT_EXPORT( FT_Error )
  FT_Outline_New_Internal( FT_Memory    memory,
                           FT_UInt      numPoints,
                           FT_Int       numContours,
                           FT_Outline  *anoutline );

Create a new outline of a given size.

FreeType error code. 0 means success.

The reason why this function takes a ‘library’ parameter is simply to use the library's memory allocator.

  FT_EXPORT( FT_Error )
  FT_Outline_Done( FT_Library   library,
                   FT_Outline*  outline );


  FT_EXPORT( FT_Error )
  FT_Outline_Done_Internal( FT_Memory    memory,
                            FT_Outline*  outline );

Destroy an outline created with FT_Outline_New.

FreeType error code. 0 means success.

If the outline's ‘owner’ field is not set, only the outline descriptor will be released.

The reason why this function takes an ‘library’ parameter is simply to use ft_mem_free().

  FT_EXPORT( FT_Error )
  FT_Outline_Copy( const FT_Outline*  source,
                   FT_Outline        *target );

Copy an outline into another one. Both objects must have the same sizes (number of points & number of contours) when this function is called.

FreeType error code. 0 means success.

  FT_EXPORT( void )
  FT_Outline_Translate( const FT_Outline*  outline,
                        FT_Pos             xOffset,
                        FT_Pos             yOffset );

Apply a simple translation to the points of an outline.

  FT_EXPORT( void )
  FT_Outline_Transform( const FT_Outline*  outline,
                        const FT_Matrix*   matrix );

Apply a simple 2x2 matrix to all of an outline's points. Useful for applying rotations, slanting, flipping, etc.

You can use FT_Outline_Translate if you need to translate the outline's points.

  FT_EXPORT( FT_Error )
  FT_Outline_Embolden( FT_Outline*  outline,
                       FT_Pos       strength );

Embolden an outline. The new outline will be at most 4 times ‘strength’ pixels wider and higher. You may think of the left and bottom borders as unchanged.

Negative ‘strength’ values to reduce the outline thickness are possible also.

FreeType error code. 0 means success.

The used algorithm to increase or decrease the thickness of the glyph doesn't change the number of points; this means that certain situations like acute angles or intersections are sometimes handled incorrectly.

If you need ‘better’ metrics values you should call FT_Outline_Get_CBox or FT_Outline_Get_BBox.

Example call:

  FT_Load_Glyph( face, index, FT_LOAD_DEFAULT );                   
  if ( face->slot->format == FT_GLYPH_FORMAT_OUTLINE )             
    FT_Outline_Embolden( &face->slot->outline, strength );         

  FT_EXPORT( FT_Error )
  FT_Outline_EmboldenXY( FT_Outline*  outline,
                         FT_Pos       xstrength,
                         FT_Pos       ystrength );

Embolden an outline. The new outline will be ‘xstrength’ pixels wider and ‘ystrength’ pixels higher. Otherwise, it is similar to FT_Outline_Embolden, which uses the same strength in both directions.

  FT_EXPORT( void )
  FT_Outline_Reverse( FT_Outline*  outline );

Reverse the drawing direction of an outline. This is used to ensure consistent fill conventions for mirrored glyphs.

This function toggles the bit flag FT_OUTLINE_REVERSE_FILL in the outline's ‘flags’ field.

It shouldn't be used by a normal client application, unless it knows what it is doing.

  FT_EXPORT( FT_Error )
  FT_Outline_Check( FT_Outline*  outline );

Check the contents of an outline descriptor.

FreeType error code. 0 means success.

  FT_EXPORT( FT_Error )
  FT_Outline_Get_BBox( FT_Outline*  outline,
                       FT_BBox     *abbox );

Compute the exact bounding box of an outline. This is slower than computing the control box. However, it uses an advanced algorithm which returns very quickly when the two boxes coincide. Otherwise, the outline Bézier arcs are traversed to extract their extrema.

FreeType error code. 0 means success.

If the font is tricky and the glyph has been loaded with FT_LOAD_NO_SCALE, the resulting BBox is meaningless. To get reasonable values for the BBox it is necessary to load the glyph at a large ppem value (so that the hinting instructions can properly shift and scale the subglyphs), then extracting the BBox which can be eventually converted back to font units.

#define ft_outline_none             FT_OUTLINE_NONE
#define ft_outline_owner            FT_OUTLINE_OWNER
#define ft_outline_even_odd_fill    FT_OUTLINE_EVEN_ODD_FILL
#define ft_outline_reverse_fill     FT_OUTLINE_REVERSE_FILL
#define ft_outline_ignore_dropouts  FT_OUTLINE_IGNORE_DROPOUTS
#define ft_outline_high_precision   FT_OUTLINE_HIGH_PRECISION
#define ft_outline_single_pass      FT_OUTLINE_SINGLE_PASS

These constants are deprecated. Please use the corresponding FT_OUTLINE_FLAGS values.

  typedef int
  (*FT_Outline_MoveToFunc)( const FT_Vector*  to,
                            void*             user );

#define FT_Outline_MoveTo_Func  FT_Outline_MoveToFunc

A function pointer type used to describe the signature of a ‘move to’ function during outline walking/decomposition.

A ‘move to’ is emitted to start a new contour in an outline.

Error code. 0 means success.

  typedef int
  (*FT_Outline_LineToFunc)( const FT_Vector*  to,
                            void*             user );

#define FT_Outline_LineTo_Func  FT_Outline_LineToFunc

A function pointer type used to describe the signature of a ‘line to’ function during outline walking/decomposition.

A ‘line to’ is emitted to indicate a segment in the outline.

Error code. 0 means success.

  typedef int
  (*FT_Outline_ConicToFunc)( const FT_Vector*  control,
                             const FT_Vector*  to,
                             void*             user );

#define FT_Outline_ConicTo_Func  FT_Outline_ConicToFunc

A function pointer type used to describe the signature of a ‘conic to’ function during outline walking or decomposition.

A ‘conic to’ is emitted to indicate a second-order Bézier arc in the outline.

Error code. 0 means success.

  typedef int
  (*FT_Outline_CubicToFunc)( const FT_Vector*  control1,
                             const FT_Vector*  control2,
                             const FT_Vector*  to,
                             void*             user );

#define FT_Outline_CubicTo_Func  FT_Outline_CubicToFunc

A function pointer type used to describe the signature of a ‘cubic to’ function during outline walking or decomposition.

A ‘cubic to’ is emitted to indicate a third-order Bézier arc.

Error code. 0 means success.

  typedef struct  FT_Outline_Funcs_
  {
    FT_Outline_MoveToFunc   move_to;
    FT_Outline_LineToFunc   line_to;
    FT_Outline_ConicToFunc  conic_to;
    FT_Outline_CubicToFunc  cubic_to;

    int                     shift;
    FT_Pos                  delta;

  } FT_Outline_Funcs;

A structure to hold various function pointers used during outline decomposition in order to emit segments, conic, and cubic Béziers.

The point coordinates sent to the emitters are the transformed version of the original coordinates (this is important for high accuracy during scan-conversion). The transformation is simple:

  x' = (x << shift) - delta                                        
  y' = (x << shift) - delta                                        

Set the values of ‘shift’ and ‘delta’ to 0 to get the original point coordinates.

  FT_EXPORT( FT_Error )
  FT_Outline_Decompose( FT_Outline*              outline,
                        const FT_Outline_Funcs*  func_interface,
                        void*                    user );

Walk over an outline's structure to decompose it into individual segments and Bézier arcs. This function also emits ‘move to’ operations to indicate the start of new contours in the outline.

FreeType error code. 0 means success.

  FT_EXPORT( void )
  FT_Outline_Get_CBox( const FT_Outline*  outline,
                       FT_BBox           *acbox );

Return an outline's ‘control box’. The control box encloses all the outline's points, including Bézier control points. Though it coincides with the exact bounding box for most glyphs, it can be slightly larger in some situations (like when rotating an outline which contains Bézier outside arcs).

Computing the control box is very fast, while getting the bounding box can take much more time as it needs to walk over all segments and arcs in the outline. To get the latter, you can use the ‘ftbbox’ component which is dedicated to this single task.

See FT_Glyph_Get_CBox for a discussion of tricky fonts.

  FT_EXPORT( FT_Error )
  FT_Outline_Get_Bitmap( FT_Library        library,
                         FT_Outline*       outline,
                         const FT_Bitmap  *abitmap );

Render an outline within a bitmap. The outline's image is simply OR-ed to the target bitmap.

FreeType error code. 0 means success.

This function does NOT CREATE the bitmap, it only renders an outline image within the one you pass to it! Consequently, the various fields in ‘abitmap’ should be set accordingly.

It will use the raster corresponding to the default glyph format.

The value of the ‘num_grays’ field in ‘abitmap’ is ignored. If you select the gray-level rasterizer, and you want less than 256 gray levels, you have to use FT_Outline_Render directly.

  FT_EXPORT( FT_Error )
  FT_Outline_Render( FT_Library         library,
                     FT_Outline*        outline,
                     FT_Raster_Params*  params );

Render an outline within a bitmap using the current scan-convert. This function uses an FT_Raster_Params structure as an argument, allowing advanced features like direct composition, translucency, etc.

FreeType error code. 0 means success.

You should know what you are doing and how FT_Raster_Params works to use this function.

The field ‘params.source’ will be set to ‘outline’ before the scan converter is called, which means that the value you give to it is actually ignored.

The gray-level rasterizer always uses 256 gray levels. If you want less gray levels, you have to provide your own span callback. See the FT_RASTER_FLAG_DIRECT value of the ‘flags’ field in the FT_Raster_Params structure for more details.

  typedef enum  FT_Orientation_
  {
    FT_ORIENTATION_TRUETYPE   = 0,
    FT_ORIENTATION_POSTSCRIPT = 1,
    FT_ORIENTATION_FILL_RIGHT = FT_ORIENTATION_TRUETYPE,
    FT_ORIENTATION_FILL_LEFT  = FT_ORIENTATION_POSTSCRIPT,
    FT_ORIENTATION_NONE

  } FT_Orientation;

A list of values used to describe an outline's contour orientation.

The TrueType and PostScript specifications use different conventions to determine whether outline contours should be filled or unfilled.

  FT_EXPORT( FT_Orientation )
  FT_Outline_Get_Orientation( FT_Outline*  outline );

This function analyzes a glyph outline and tries to compute its fill orientation (see FT_Orientation). This is done by computing the direction of each global horizontal and/or vertical extrema within the outline.

Note that this will return FT_ORIENTATION_TRUETYPE for empty outlines.

The orientation.