freetype2/include/freetype/ftimage.h

/***************************************************************************/
/*                                                                         */
/*  ftimage.h                                                              */
/*                                                                         */
/*    FreeType glyph image formats and default raster interface            */
/*    (specification).                                                     */
/*                                                                         */
/*  Copyright 1996-2000 by                                                 */
/*  David Turner, Robert Wilhelm, and Werner Lemberg.                      */
/*                                                                         */
/*  This file is part of the FreeType project, and may only be used,       */
/*  modified, and distributed under the terms of the FreeType project      */
/*  license, LICENSE.TXT.  By continuing to use, modify, or distribute     */
/*  this file you indicate that you have read the license and              */
/*  understand and accept it fully.                                        */
/*                                                                         */
/***************************************************************************/

  /*************************************************************************/
  /*                                                                       */
  /* Note: A `raster' is simply a scan-line converter, used to render      */
  /*       FT_Outlines into FT_Bitmaps.                                    */
  /*                                                                       */
  /*************************************************************************/


#ifndef __FTIMAGE_H__
#define __FTIMAGE_H__


#ifndef    FT_BUILD_H
#  define  FT_BUILD_H    <freetype/config/ftbuild.h>
#endif
#include   FT_BUILD_H

FT_BEGIN_HEADER


  /*************************************************************************/
  /*                                                                       */
  /* <Type>                                                                */
  /*    FT_Pos                                                             */
  /*                                                                       */
  /* <Description>                                                         */
  /*    The type FT_Pos is a 32-bit integer used to store vectorial        */
  /*    coordinates.  Depending on the context, these can represent        */
  /*    distances in integer font units, or 26.6 fixed float pixel         */
  /*    coordinates.                                                       */
  /*                                                                       */
  typedef signed long  FT_Pos;


  /*************************************************************************/
  /*                                                                       */
  /* <Struct>                                                              */
  /*    FT_Vector                                                          */
  /*                                                                       */
  /* <Description>                                                         */
  /*    A simple structure used to store a 2D vector; coordinates are of   */
  /*    the FT_Pos type.                                                   */
  /*                                                                       */
  /* <Fields>                                                              */
  /*    x :: The horizontal coordinate.                                    */
  /*    y :: The vertical coordinate.                                      */
  /*                                                                       */
  typedef struct  FT_Vector_
  {
    FT_Pos  x;
    FT_Pos  y;

  } FT_Vector;


  /*************************************************************************/
  /*                                                                       */
  /* <Enum>                                                                */
  /*    FT_Pixel_Mode                                                      */
  /*                                                                       */
  /* <Description>                                                         */
  /*    An enumeration type used to describe the format of pixels in a     */
  /*    given bitmap.  Note that additional formats may be added in the    */
  /*    future.                                                            */
  /*                                                                       */
  /* <Fields>                                                              */
  /*    ft_pixel_mode_mono  :: A monochrome bitmap (1 bit/pixel).          */
  /*                                                                       */
  /*    ft_pixel_mode_grays :: An 8-bit gray-levels bitmap.  Note that the */
  /*                           total number of gray levels is given in the */
  /*                           `num_grays' field of the FT_Bitmap          */
  /*                           structure.                                  */
  /*                                                                       */
  /*    ft_pixel_mode_pal2  :: A 2-bit paletted bitmap.                    */
  /*                           Currently unused by FreeType.               */
  /*                                                                       */
  /*    ft_pixel_mode_pal4  :: A 4-bit paletted bitmap.                    */
  /*                           Currently unused by FreeType.               */
  /*                                                                       */
  /*    ft_pixel_mode_pal8  :: An 8-bit paletted bitmap.                   */
  /*                           Currently unused by FreeType.               */
  /*                                                                       */
  /*    ft_pixel_mode_rgb15 :: A 15-bit RGB bitmap.  Uses 5:5:5 encoding.  */
  /*                           Currently unused by FreeType.               */
  /*                                                                       */
  /*    ft_pixel_mode_rgb16 :: A 16-bit RGB bitmap.  Uses 5:6:5 encoding.  */
  /*                           Currently unused by FreeType.               */
  /*                                                                       */
  /*    ft_pixel_mode_rgb24 :: A 24-bit RGB bitmap.                        */
  /*                           Currently unused by FreeType.               */
  /*                                                                       */
  /*    ft_pixel_mode_rgb32 :: A 32-bit RGB bitmap.                        */
  /*                           Currently unused by FreeType.               */
  /*                                                                       */
  /* <Note>                                                                */
  /*    Some anti-aliased bitmaps might be embedded in TrueType fonts      */
  /*    using formats pal2 or pal4, though no fonts presenting those have  */
  /*    been found to date.                                                */
  /*                                                                       */
  typedef enum  FT_Pixel_Mode_
  {
    ft_pixel_mode_none = 0,
    ft_pixel_mode_mono,
    ft_pixel_mode_grays,
    ft_pixel_mode_pal2,
    ft_pixel_mode_pal4,
    ft_pixel_mode_pal8,
    ft_pixel_mode_rgb15,
    ft_pixel_mode_rgb16,
    ft_pixel_mode_rgb24,
    ft_pixel_mode_rgb32,

    ft_pixel_mode_max      /* do not remove */

  } FT_Pixel_Mode;


  /*************************************************************************/
  /*                                                                       */
  /* <Enum>                                                                */
  /*    FT_Palette_Mode                                                    */
  /*                                                                       */
  /* <Description>                                                         */
  /*    An enumeration type used to describe the format of a bitmap        */
  /*    palette, used with ft_pixel_mode_pal4 and ft_pixel_mode_pal8.      */
  /*                                                                       */
  /* <Fields>                                                              */
  /*    ft_palette_mode_rgb  :: The palette is an array of 3-bytes RGB     */
  /*                            records.                                   */
  /*                                                                       */
  /*    ft_palette_mode_rgba :: The palette is an array of 4-bytes RGBA    */
  /*                            records.                                   */
  /*                                                                       */
  /* <Note>                                                                */
  /*    As ft_pixel_mode_pal2, pal4 and pal8 are currently unused by       */
  /*    FreeType, these types are not handled by the library itself.       */
  /*                                                                       */
  typedef enum  FT_Palette_Mode_
  {
    ft_palette_mode_rgb = 0,
    ft_palette_mode_rgba,

    ft_palettte_mode_max   /* do not remove */

  } FT_Palette_Mode;


  /*************************************************************************/
  /*                                                                       */
  /* <Struct>                                                              */
  /*    FT_Bitmap                                                          */
  /*                                                                       */
  /* <Description>                                                         */
  /*    A structure used to describe a bitmap or pixmap to the raster.     */
  /*    Note that we now manage pixmaps of various depths through the      */
  /*    `pixel_mode' field.                                                */
  /*                                                                       */
  /* <Fields>                                                              */
  /*    rows         :: The number of bitmap rows.                         */
  /*                                                                       */
  /*    width        :: The number of pixels in bitmap row.                */
  /*                                                                       */
  /*    pitch        :: The pitch's absolute value is the number of bytes  */
  /*                    taken by one bitmap row, including padding.        */
  /*                    However, the pitch is positive when the bitmap has */
  /*                    a `down' flow, and negative when it has an `up'    */
  /*                    flow.  In all cases, the pitch is an offset to add */
  /*                    to a bitmap pointer in order to go down one row.   */
  /*                                                                       */
  /*    buffer       :: A typeless pointer to the bitmap buffer.  This     */
  /*                    value should be aligned on 32-bit boundaries in    */
  /*                    most cases.                                        */
  /*                                                                       */
  /*    num_grays    :: This field is only used with                       */
  /*                    `ft_pixel_mode_grays'; it gives the number of gray */
  /*                    levels used in the bitmap.                         */
  /*                                                                       */
  /*    pixel_mode   :: The pixel_mode, i.e., how pixel bits are stored.   */
  /*                                                                       */
  /*    palette_mode :: This field is only used with paletted pixel modes; */
  /*                    it indicates how the palette is stored.            */
  /*                                                                       */
  /*    palette      :: A typeless pointer to the bitmap palette; only     */
  /*                    used for paletted pixel modes.                     */
  /*                                                                       */
  /* <Note>                                                                */
  /*   For now, the only pixel mode supported by FreeType are mono and     */
  /*   grays.  However, drivers might be added in the future to support    */
  /*   more `colorful' options.                                            */
  /*                                                                       */
  /*   When using pixel modes pal2, pal4 and pal8 with a void `palette'    */
  /*   field, a gray pixmap with respectively 4, 16, and 256 levels of     */
  /*   gray is assumed.  This, in order to be compatible with some         */
  /*   embedded bitmap formats defined in the TrueType specification.      */
  /*                                                                       */
  /*   Note that no font was found presenting such embedded bitmaps, so    */
  /*   this is currently completely unhandled by the library.              */
  /*                                                                       */
  typedef struct  FT_Bitmap_
  {
    int             rows;
    int             width;
    int             pitch;
    unsigned char*  buffer;
    short           num_grays;
    char            pixel_mode;
    char            palette_mode;
    void*           palette;

  } FT_Bitmap;


  /*************************************************************************/
  /*                                                                       */
  /* <Struct>                                                              */
  /*    FT_Outline                                                         */
  /*                                                                       */
  /* <Description>                                                         */
  /*    This structure is used to describe an outline to the scan-line     */
  /*    converter.                                                         */
  /*                                                                       */
  /* <Fields>                                                              */
  /*    n_contours :: The number of contours in the outline.               */
  /*                                                                       */
  /*    n_points   :: The number of points in the outline.                 */
  /*                                                                       */
  /*    points     :: A pointer to an array of `n_points' FT_Vector        */
  /*                  elements, giving the outline's point coordinates.    */
  /*                                                                       */
  /*    tags       :: A pointer to an array of `n_points' chars, giving    */
  /*                  giving each outline point's type.  If bit 0 is       */
  /*                  unset, the point is 'off' the curve, i.e. a Bezier   */
  /*                  control point, while it is `on' when set.            */
  /*                                                                       */
  /*                  Bit 1 is meaningful for `off' points only.  If set,  */
  /*                  it indicates a third-order Bezier arc control point; */
  /*                  and a second-order control point if unset.           */
  /*                                                                       */
  /*    contours   :: An array of `n_contours' shorts, giving the end      */
  /*                  point of each contour within the outline.  For       */
  /*                  example, the first contour is defined by the points  */
  /*                  `0' to `contours[0]', the second one is defined by   */
  /*                  the points `contours[0]+1' to `contours[1]', etc.    */
  /*                                                                       */
  /*    flags      :: A set of bit flags used to characterize the outline  */
  /*                  and give hints to the scan-converter and hinter on   */
  /*                  how to convert/grid-fit it.  See FT_Outline_Flags.   */
  /*                                                                       */
  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;


  /*************************************************************************/
  /*                                                                       */
  /* <Enum>                                                                */
  /*   FT_Outline_Flags                                                    */
  /*                                                                       */
  /* <Description>                                                         */
  /*    A simple type used to enumerates the flags in an outline's         */
  /*    `outline_flags' field.                                             */
  /*                                                                       */
  /* <Fields>                                                              */
  /*    ft_outline_owner          :: If set, this flag indicates that the  */
  /*                                 outline's field arrays (i.e.          */
  /*                                 `points', `flags' & `contours') are   */
  /*                                 `owned' by the outline object, and    */
  /*                                 should thus be freed when it is       */
  /*                                 destroyed.                            */
  /*                                                                       */
  /*   ft_outline_even_odd_fill   :: By default, outlines are filled using */
  /*                                 the non-zero winding rule.  If set to */
  /*                                 1, the outline will be filled using   */
  /*                                 the even-odd fill rule (only works    */
  /*                                 with the smooth raster).              */
  /*                                                                       */
  /*   ft_outline_reverse_fill    :: By default, outside contours of an    */
  /*                                 outline are oriented in clock-wise    */
  /*                                 direction, as defined in the TrueType */
  /*                                 specification.  This flag is set if   */
  /*                                 the outline uses the opposite         */
  /*                                 direction (typically for Type 1       */
  /*                                 fonts).  This flag is ignored by the  */
  /*                                 scan-converter.  However, it is very  */
  /*                                 important for the auto-hinter.        */
  /*                                                                       */
  /*   ft_outline_ignore_dropouts :: By default, the scan converter will   */
  /*                                 try to detect drop-outs in an outline */
  /*                                 and correct the glyph bitmap to       */
  /*                                 ensure consistent shape continuity.   */
  /*                                 If set, this flag hints the scan-line */
  /*                                 converter to ignore such cases.       */
  /*                                                                       */
  /*   ft_outline_high_precision  :: This flag indicates that the          */
  /*                                 scan-line converter should try to     */
  /*                                 convert this outline to bitmaps with  */
  /*                                 the highest possible quality.  It is  */
  /*                                 typically set for small character     */
  /*                                 sizes.  Note that this is only a      */
  /*                                 hint, that might be completely        */
  /*                                 ignored by a given scan-converter.    */
  /*                                                                       */
  /*   ft_outline_single_pass     :: This flag is set to force a given     */
  /*                                 scan-converter to only use a single   */
  /*                                 pass over the outline to render a     */
  /*                                 bitmap glyph image.  Normally, it is  */
  /*                                 set for very large character sizes.   */
  /*                                 It is only a hint, that might be      */
  /*                                 completely ignored by a given         */
  /*                                 scan-converter.                       */
  /*                                                                       */
  typedef enum  FT_Outline_Flags_
  {
    ft_outline_none            = 0,
    ft_outline_owner           = 1,
    ft_outline_even_odd_fill   = 2,
    ft_outline_reverse_fill    = 4,
    ft_outline_ignore_dropouts = 8,
    ft_outline_high_precision  = 256,
    ft_outline_single_pass     = 512

  } FT_Outline_Flags;


#define FT_CURVE_TAG( flag )  ( flag & 3 )

#define FT_Curve_Tag_On           1
#define FT_Curve_Tag_Conic        0
#define FT_Curve_Tag_Cubic        2

#define FT_Curve_Tag_Touch_X      8  /* reserved for the TrueType hinter */
#define FT_Curve_Tag_Touch_Y     16  /* reserved for the TrueType hinter */

#define FT_Curve_Tag_Touch_Both  ( FT_Curve_Tag_Touch_X | \
                                   FT_Curve_Tag_Touch_Y )


  /*************************************************************************/
  /*                                                                       */
  /* <FuncType>                                                            */
  /*    FT_Outline_MoveTo_Func                                             */
  /*                                                                       */
  /* <Description>                                                         */
  /*    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.       */
  /*                                                                       */
  /* <Input>                                                               */
  /*    to   :: A pointer to the target point of the `move to'.            */
  /*                                                                       */
  /*    user :: A typeless pointer which is passed from the caller of the  */
  /*            decomposition function.                                    */
  /*                                                                       */
  /* <Return>                                                              */
  /*    Error code.  0 means success.                                      */
  /*                                                                       */
  typedef int  (*FT_Outline_MoveTo_Func)( FT_Vector*  to,
                                          void*       user );


  /*************************************************************************/
  /*                                                                       */
  /* <FuncType>                                                            */
  /*    FT_Outline_LineTo_Func                                             */
  /*                                                                       */
  /* <Description>                                                         */
  /*    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.       */
  /*                                                                       */
  /* <Input>                                                               */
  /*    to   :: A pointer to the target point of the `line to'.            */
  /*                                                                       */
  /*    user :: A typeless pointer which is passed from the caller of the  */
  /*            decomposition function.                                    */
  /*                                                                       */
  /* <Return>                                                              */
  /*    Error code.  0 means success.                                      */
  /*                                                                       */
  typedef int  (*FT_Outline_LineTo_Func)( FT_Vector*  to,
                                          void*       user );


  /*************************************************************************/
  /*                                                                       */
  /* <FuncType>                                                            */
  /*    FT_Outline_ConicTo_Func                                            */
  /*                                                                       */
  /* <Description>                                                         */
  /*    A function pointer type use to describe the signature of a `conic  */
  /*    to' function during outline walking/decomposition.                 */
  /*                                                                       */
  /*    A `conic to' is emitted to indicate a second-order Bezier arc in   */
  /*    the outline.                                                       */
  /*                                                                       */
  /* <Input>                                                               */
  /*    control :: An intermediate control point between the last position */
  /*               and the new target in `to'.                             */
  /*                                                                       */
  /*    to      :: A pointer to the target end point of the conic arc.     */
  /*                                                                       */
  /*    user    :: A typeless pointer which is passed from the caller of   */
  /*               the decomposition function.                             */
  /*                                                                       */
  /* <Return>                                                              */
  /*    Error code.  0 means success.                                      */
  /*                                                                       */
  typedef int  (*FT_Outline_ConicTo_Func)( FT_Vector*  control,
                                           FT_Vector*  to,
                                           void*       user );


  /*************************************************************************/
  /*                                                                       */
  /* <FuncType>                                                            */
  /*    FT_Outline_CubicTo_Func                                            */
  /*                                                                       */
  /* <Description>                                                         */
  /*    A function pointer type used to describe the signature of a `cubic */
  /*    to' function during outline walking/decomposition.                 */
  /*                                                                       */
  /*    A `cubic to' is emitted to indicate a third-order Bezier arc.      */
  /*                                                                       */
  /* <Input>                                                               */
  /*    control1 :: A pointer to the first Bezier control point.           */
  /*                                                                       */
  /*    control2 :: A pointer to the second Bezier control point.          */
  /*                                                                       */
  /*    to       :: A pointer to the target end point.                     */
  /*                                                                       */
  /*    user     :: A typeless pointer which is passed from the caller of  */
  /*                the decomposition function.                            */
  /*                                                                       */
  /* <Return>                                                              */
  /*    Error code.  0 means success.                                      */
  /*                                                                       */
  typedef int  (*FT_Outline_CubicTo_Func)( FT_Vector*  control1,
                                           FT_Vector*  control2,
                                           FT_Vector*  to,
                                           void*       user );


  /*************************************************************************/
  /*                                                                       */
  /* <Struct>                                                              */
  /*    FT_Outline_Funcs                                                   */
  /*                                                                       */
  /* <Description>                                                         */
  /*    A structure to hold various function pointers used during outline  */
  /*    decomposition in order to emit segments, conic, and cubic Beziers, */
  /*    as well as `move to' and `close to' operations.                    */
  /*                                                                       */
  /* <Fields>                                                              */
  /*    move_to  :: The `move to' emitter.                                 */
  /*                                                                       */
  /*    line_to  :: The segment emitter.                                   */
  /*                                                                       */
  /*    conic_to :: The second-order Bezier arc emitter.                   */
  /*                                                                       */
  /*    cubic_to :: The third-order Bezier arc emitter.                    */
  /*                                                                       */
  /*    shift    :: The shift that is applied to coordinates before they   */
  /*                are sent to the emitter.                               */
  /*                                                                       */
  /*    delta    :: The delta that is applied to coordinates before they   */
  /*                are sent to the emitter, but after the shift.          */
  /*                                                                       */
  /* <Note>                                                                */
  /*    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 value of `shift' and `delta' to 0 to get the original      */
  /*    point coordinates.                                                 */
  /*                                                                       */
  typedef struct  FT_Outline_Funcs_
  {
    FT_Outline_MoveTo_Func   move_to;
    FT_Outline_LineTo_Func   line_to;
    FT_Outline_ConicTo_Func  conic_to;
    FT_Outline_CubicTo_Func  cubic_to;

    int                      shift;
    FT_Pos                   delta;

  } FT_Outline_Funcs;


  /*************************************************************************/
  /*                                                                       */
  /* <Macro>                                                               */
  /*    FT_IMAGE_TAG                                                       */
  /*                                                                       */
  /* <Description>                                                         */
  /*    This macro converts four letter tags into an unsigned long.        */
  /*                                                                       */
#define FT_IMAGE_TAG( _x1, _x2, _x3, _x4 ) \
          ( ( (unsigned long)_x1 << 24 ) | \
            ( (unsigned long)_x2 << 16 ) | \
            ( (unsigned long)_x3 << 8  ) | \
              (unsigned long)_x4         )


  /*************************************************************************/
  /*                                                                       */
  /* <Enum>                                                                */
  /*    FT_Glyph_Format                                                    */
  /*                                                                       */
  /* <Description>                                                         */
  /*    An enumeration type used to describe the format of a given glyph   */
  /*    image.  Note that this version of FreeType only supports two image */
  /*    formats, even though future font drivers will be able to register  */
  /*    their own format.                                                  */
  /*                                                                       */
  /* <Fields>                                                              */
  /*    ft_glyph_format_composite :: The glyph image is a composite of     */
  /*                                 several other images.  This glyph     */
  /*                                 format is _only_ used with the        */
  /*                                 FT_LOAD_FLAG_NO_RECURSE flag (XXX:    */
  /*                                 Which is currently unimplemented).    */
  /*                                                                       */
  /*    ft_glyph_format_bitmap    :: The glyph image is a bitmap, and can  */
  /*                                 be described as a FT_Bitmap.          */
  /*                                                                       */
  /*    ft_glyph_format_outline   :: The glyph image is a vectorial image  */
  /*                                 made of bezier control points, and    */
  /*                                 can be described as a FT_Outline.     */
  /*                                                                       */
  /*    ft_glyph_format_plotter   :: The glyph image is a vectorial image  */
  /*                                 made of plotter lines (some T1 fonts  */
  /*                                 like Hershey contain glyph in this    */
  /*                                 format).                              */
  /*                                                                       */
  typedef enum  FT_Glyph_Format_
  {
    ft_glyph_format_none      = 0,
    ft_glyph_format_composite = FT_IMAGE_TAG( 'c', 'o', 'm', 'p' ),
    ft_glyph_format_bitmap    = FT_IMAGE_TAG( 'b', 'i', 't', 's' ),
    ft_glyph_format_outline   = FT_IMAGE_TAG( 'o', 'u', 't', 'l' ),
    ft_glyph_format_plotter   = FT_IMAGE_TAG( 'p', 'l', 'o', 't' )

  } FT_Glyph_Format;


  /*************************************************************************/
  /*************************************************************************/
  /*************************************************************************/
  /*****                                                               *****/
  /*****            R A S T E R   D E F I N I T I O N S                *****/
  /*****                                                               *****/
  /*************************************************************************/
  /*************************************************************************/
  /*************************************************************************/


  /*************************************************************************/
  /*                                                                       */
  /* A raster is a scan converter, in charge of rendering an outline into  */
  /* a a bitmap.  This section contains the public API for rasters.        */
  /*                                                                       */
  /* Note that in FreeType 2, all rasters are now encapsulated within      */
  /* specific modules called `renderers'.  See `freetype/ftrender.h' for   */
  /* more details on renderers.                                            */
  /*                                                                       */
  /*************************************************************************/


  /*************************************************************************/
  /*                                                                       */
  /* <Type>                                                                */
  /*    FT_Raster                                                          */
  /*                                                                       */
  /* <Description>                                                         */
  /*    A handle (pointer) to a raster object.  Each object can be used    */
  /*    independently to convert an outline into a bitmap or pixmap.       */
  /*                                                                       */
  typedef struct FT_RasterRec_*  FT_Raster;


  /*************************************************************************/
  /*                                                                       */
  /* <Struct>                                                              */
  /*    FT_Span                                                            */
  /*                                                                       */
  /* <Description>                                                         */
  /*    A structure used to model a single span of gray (or black) pixels  */
  /*    when rendering a monochrome or anti-aliased bitmap.                */
  /*                                                                       */
  /* <Fields>                                                              */
  /*    x        :: The span's horizontal start position.                  */
  /*                                                                       */
  /*    len      :: The span's length in pixels.                           */
  /*                                                                       */
  /*    coverage :: The span color/coverage, ranging from 0 (background)   */
  /*                to 255 (foreground).  Only used for anti-aliased       */
  /*                rendering.                                             */
  /*                                                                       */
  /* <Note>                                                                */
  /*    This structure is used by the span drawing callback type named     */
  /*    FT_Raster_Span_Func(), which takes the y-coordinate of the span as */
  /*    a parameter.                                                       */
  /*                                                                       */
  /*    The coverage value is always between 0 and 255, even if the number */
  /*    of gray levels have been set through FT_Set_Gray_Levels().         */
  /*                                                                       */
  typedef struct  FT_Span_
  {
    short          x;
    unsigned short len;
    unsigned char  coverage;

  } FT_Span;


  /*************************************************************************/
  /*                                                                       */
  /* <FuncType>                                                            */
  /*    FT_Raster_Span_Func                                                */
  /*                                                                       */
  /* <Description>                                                         */
  /*    A function used as a call-back by the anti-aliased renderer in     */
  /*    order to let client applications draw themselves the gray pixel    */
  /*    spans on each scan line.                                           */
  /*                                                                       */
  /* <Input>                                                               */
  /*    y     :: The scanline's y-coordinate.                              */
  /*                                                                       */
  /*    count :: The number of spans to draw on this scanline.             */
  /*                                                                       */
  /*    spans :: A table of `count' spans to draw on the scanline.         */
  /*                                                                       */
  /*    user  :: User-supplied data that is passed to the callback.        */
  /*                                                                       */
  /* <Note>                                                                */
  /*    This callback allows client applications to directly render the    */
  /*    gray spans of the anti-aliased bitmap to any kind of surfaces.     */
  /*                                                                       */
  /*    This can be used to write anti-aliased outlines directly to a      */
  /*    given background bitmap, and even perform translucency.            */
  /*                                                                       */
  /*    Note that the `count' field cannot be greater than a fixed value   */
  /*    defined by the FT_MAX_GRAY_SPANS configuration macro in            */
  /*    ftoption.h.  By default, this value is set to 32, which means that */
  /*    if there are more than 32 spans on a given scanline, the callback  */
  /*    will be called several times with the same `y' parameter in order  */
  /*    to draw all callbacks.                                             */
  /*                                                                       */
  /*    Otherwise, the callback is only called once per scan-line, and     */
  /*    only for those scanlines that do have `gray' pixels on them.       */
  /*                                                                       */
  typedef void  (*FT_Raster_Span_Func)( int       y,
                                        int       count,
                                        FT_Span*  spans,
                                        void*     user );


  /*************************************************************************/
  /*                                                                       */
  /* <FuncType>                                                            */
  /*    FT_Raster_BitTest_Func                                             */
  /*                                                                       */
  /* <Description>                                                         */
  /*    A function used as a call-back by the monochrome scan-converter    */
  /*    to test whether a given target pixel is already set to the drawing */
  /*    `color'.  These tests are crucial to implement drop-out control    */
  /*    per-se the TrueType spec.                                          */
  /*                                                                       */
  /* <Input>                                                               */
  /*    y     :: The pixel's y-coordinate.                                 */
  /*                                                                       */
  /*    x     :: The pixel's x-coordinate.                                 */
  /*                                                                       */
  /*    user  :: User-supplied data that is passed to the callback.        */
  /*                                                                       */
  /* <Return>                                                              */
  /*   1 if the pixel is `set', 0 otherwise.                               */
  /*                                                                       */
  typedef int  (*FT_Raster_BitTest_Func)( int    y,
                                          int    x,
                                          void*  user );


  /*************************************************************************/
  /*                                                                       */
  /* <FuncType>                                                            */
  /*    FT_Raster_BitSet_Func                                              */
  /*                                                                       */
  /* <Description>                                                         */
  /*    A function used as a call-back by the monochrome scan-converter    */
  /*    to set an individual target pixel.  This is crucial to implement   */
  /*    drop-out control according to the TrueType specification.          */
  /*                                                                       */
  /* <Input>                                                               */
  /*    y     :: The pixel's y-coordinate.                                 */
  /*                                                                       */
  /*    x     :: The pixel's x-coordinate.                                 */
  /*                                                                       */
  /*    user  :: User-supplied data that is passed to the callback.        */
  /*                                                                       */
  /* <Return>                                                              */
  /*    1 if the pixel is `set', 0 otherwise.                              */
  /*                                                                       */
  typedef void  (*FT_Raster_BitSet_Func)( int    y,
                                          int    x,
                                          void*  user );


  /*************************************************************************/
  /*                                                                       */
  /* <Enum>                                                                */
  /*    FT_Raster_Flag                                                     */
  /*                                                                       */
  /* <Description>                                                         */
  /*    An enumeration to list the bit flags as used in the `flags' field  */
  /*    of a FT_Raster_Params structure.                                   */
  /*                                                                       */
  /* <Fields>                                                              */
  /*    ft_raster_flag_default :: This value is 0.                         */
  /*                                                                       */
  /*    ft_raster_flag_aa      :: Requests the rendering of an             */
  /*                              anti-aliased glyph bitmap.  If unset, a  */
  /*                              monchrome bitmap will be rendered.       */
  /*                                                                       */
  /*    ft_raster_flag_direct  :: Requests direct rendering over the       */
  /*                              target bitmap.  Direct rendering uses    */
  /*                              user-provided callbacks in order to      */
  /*                              perform direct drawing or composition    */
  /*                              over an existing bitmap.  If this bit is */
  /*                              unset, the content of the target bitmap  */
  /*                              *must be zeroed*!                        */
  /*                                                                       */
  typedef  enum
  {
    ft_raster_flag_default = 0,
    ft_raster_flag_aa      = 1,
    ft_raster_flag_direct  = 2

  } FT_Raster_Flag;


  /*************************************************************************/
  /*                                                                       */
  /* <Struct>                                                              */
  /*    FT_Raster_Params                                                   */
  /*                                                                       */
  /* <Description>                                                         */
  /*    A structure to hold the arguments used by a raster's render        */
  /*    function.                                                          */
  /*                                                                       */
  /* <Fields>                                                              */
  /*    target      :: The target bitmap.                                  */
  /*                                                                       */
  /*    source      :: A pointer to the source glyph image (e.g. an        */
  /*                   FT_Outline).                                        */
  /*                                                                       */
  /*    flags       :: The rendering flags.                                */
  /*                                                                       */
  /*    gray_spans  :: The gray span drawing callback.                     */
  /*                                                                       */
  /*    black_spans :: The black span drawing callback.                    */
  /*                                                                       */
  /*    bit_test    :: The bit test callback.                              */
  /*                                                                       */
  /*    bit_set     :: The bit set callback.                               */
  /*                                                                       */
  /*    user        :: User-supplied data that is passed to each drawing   */
  /*                   callback.                                           */
  /*                                                                       */
  /* <Note>                                                                */
  /*    An anti-aliased glyph bitmap is drawn if the ft_raster_flag_aa bit */
  /*    flag is set in the `flags' field, otherwise a monochrome bitmap    */
  /*    will be generated.                                                 */
  /*                                                                       */
  /*    If the ft_raster_flag_direct bit flag is set in `flags', the       */
  /*    raster will call the `gray_spans' callback to draw gray pixel      */
  /*    spans, in the case of an aa glyph bitmap, it will call             */
  /*    `black_spans', and `bit_test' and `bit_set' in the case of a       */
  /*    monochrome bitmap.  This allows direct composition over a          */
  /*    pre-existing bitmap through user-provided callbacks to perform the */
  /*    span drawing/composition.                                          */
  /*                                                                       */
  /*    Note that the `bit_test' and `bit_set' callbacks are required when */
  /*    rendering a monochrome bitmap, as they are crucial to implement    */
  /*    correct drop-out control as defined in the TrueType specification. */
  /*                                                                       */
  typedef struct  FT_Raster_Params_
  {
    FT_Bitmap*              target;
    void*                   source;
    int                     flags;
    FT_Raster_Span_Func     gray_spans;
    FT_Raster_Span_Func     black_spans;
    FT_Raster_BitTest_Func  bit_test;
    FT_Raster_BitSet_Func   bit_set;
    void*                   user;

  } FT_Raster_Params;


  /*************************************************************************/
  /*                                                                       */
  /* <FuncType>                                                            */
  /*    FT_Raster_New_Func                                                 */
  /*                                                                       */
  /* <Description>                                                         */
  /*    A function used to create a new raster object.                     */
  /*                                                                       */
  /* <Input>                                                               */
  /*    memory :: A handle to the memory allocator.                        */
  /*                                                                       */
  /* <Output>                                                              */
  /*    raster :: A handle to the new raster object.                       */
  /*                                                                       */
  /* <Return>                                                              */
  /*    Error code.  0 means success.                                      */
  /*                                                                       */
  /* <Note>                                                                */
  /*    The `memory' parameter is a typeless pointer in order to avoid     */
  /*    un-wanted dependencies on the rest of the FreeType code.  In       */
  /*    practice, it is a FT_Memory, i.e., a handle to the standard        */
  /*    FreeType memory allocator.  However, this field can be completely  */
  /*    ignored by a given raster implementation.                          */
  /*                                                                       */
  typedef int  (*FT_Raster_New_Func)( void*       memory,
                                      FT_Raster*  raster );


  /*************************************************************************/
  /*                                                                       */
  /* <FuncType>                                                            */
  /*    FT_Raster_Done_Func                                                */
  /*                                                                       */
  /* <Description>                                                         */
  /*    A function used to destroy a given raster object.                  */
  /*                                                                       */
  /* <Input>                                                               */
  /*    raster :: A handle to the raster object.                           */
  /*                                                                       */
  typedef void  (*FT_Raster_Done_Func)( FT_Raster  raster );


  /*************************************************************************/
  /*                                                                       */
  /* <FuncType>                                                            */
  /*    FT_Raster_Reset_Func                                               */
  /*                                                                       */
  /* <Description>                                                         */
  /*    FreeType provides an area of memory called the `render pool',      */
  /*    available to all registered rasters.  This pool can be freely used */
  /*    during a given scan-conversion but is shared by all rasters.  Its  */
  /*    content is thus transient.                                         */
  /*                                                                       */
  /*    This function is called each time the render pool changes, or just */
  /*    after a new raster object is created.                              */
  /*                                                                       */
  /* <Input>                                                               */
  /*    raster    :: A handle to the new raster object.                    */
  /*                                                                       */
  /*    pool_base :: The address in memory of the render pool.             */
  /*                                                                       */
  /*    pool_size :: The size in bytes of the render pool.                 */
  /*                                                                       */
  /* <Note>                                                                */
  /*    Rasters can ignore the render pool and rely on dynamic memory      */
  /*    allocation if they want to (a handle to the memory allocator is    */
  /*    passed to the raster constructor).  However, this is not           */
  /*    recommended for efficiency purposes.                               */
  /*                                                                       */
  typedef void  (*FT_Raster_Reset_Func)( FT_Raster       raster,
                                         unsigned char*  pool_base,
                                         unsigned long   pool_size );


  /*************************************************************************/
  /*                                                                       */
  /* <FuncType>                                                            */
  /*    FT_Raster_Set_Mode_Func                                            */
  /*                                                                       */
  /* <Description>                                                         */
  /*    This function is a generic facility to change modes or attributes  */
  /*    in a given raster.  This can be used for debugging purposes, or    */
  /*    simply to allow implementation-specific `features' in a given      */
  /*    raster module.                                                     */
  /*                                                                       */
  /* <Input>                                                               */
  /*    raster :: A handle to the new raster object.                       */
  /*                                                                       */
  /*    mode   :: A 4-byte tag used to name the mode or property.          */
  /*                                                                       */
  /*    args   :: A pointer to the new mode/property to use.               */
  /*                                                                       */
  typedef int  (*FT_Raster_Set_Mode_Func)( FT_Raster      raster,
                                           unsigned long  mode,
                                           void*          args );


  /*************************************************************************/
  /*                                                                       */
  /* <FuncType>                                                            */
  /*    FT_Raster_Render_Func                                              */
  /*                                                                       */
  /* <Description>                                                         */
  /*   Invokes a given raster to scan-convert a given glyph image into a   */
  /*   target bitmap.                                                      */
  /*                                                                       */
  /* <Input>                                                               */
  /*    raster :: A handle to the raster object.                           */
  /*                                                                       */
  /*    params :: A pointer to a FT_Raster_Params structure used to store  */
  /*              the rendering parameters.                                */
  /*                                                                       */
  /* <Return>                                                              */
  /*    Error code.  0 means success.                                      */
  /*                                                                       */
  /* <Note>                                                                */
  /*    The exact format of the source image depends on the raster's glyph */
  /*    format defined in its FT_Raster_Funcs structure.  It can be an     */
  /*    FT_Outline or anything else in order to support a large array of   */
  /*    glyph formats.                                                     */
  /*                                                                       */
  /*    Note also that the render function can fail and return a           */
  /*    FT_Err_Unimplemented_Feature error code if the raster used does    */
  /*    not support direct composition.                                    */
  /*                                                                       */
  /*    XXX: For now, the standard raster doesn't support direct           */
  /*         composition but this should change for the final release (see */
  /*         the files demos/src/ftgrays.c and demos/src/ftgrays2.c for    */
  /*         examples of distinct implementations which support direct     */
  /*         composition).                                                 */
  /*                                                                       */
  typedef int  (*FT_Raster_Render_Func)( FT_Raster          raster,
                                         FT_Raster_Params*  params );


  /*************************************************************************/
  /*                                                                       */
  /* <Struct>                                                              */
  /*    FT_Raster_Funcs                                                    */
  /*                                                                       */
  /* <Description>                                                         */
  /*   A structure used to describe a given raster class to the library.   */
  /*                                                                       */
  /* <Fields>                                                              */
  /*    glyph_format  :: The supported glyph format for this raster.       */
  /*                                                                       */
  /*    raster_new    :: The raster constructor.                           */
  /*                                                                       */
  /*    raster_reset  :: Used to reset the render pool within the raster.  */
  /*                                                                       */
  /*    raster_render :: A function to render a glyph into a given bitmap. */
  /*                                                                       */
  /*    raster_done   :: The raster destructor.                            */
  /*                                                                       */
  typedef struct  FT_Raster_Funcs_
  {
    FT_Glyph_Format          glyph_format;
    FT_Raster_New_Func       raster_new;
    FT_Raster_Reset_Func     raster_reset;
    FT_Raster_Set_Mode_Func  raster_set_mode;
    FT_Raster_Render_Func    raster_render;
    FT_Raster_Done_Func      raster_done;

  } FT_Raster_Funcs;


FT_END_HEADER


#endif /* __FTIMAGE_H__ */


/* END */