ftimage.h

a very goog book

  /*                                                                       */
  /*    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_IMAGE_TAG( ft_glyph_format_none, 0, 0, 0, 0 ),

    FT_IMAGE_TAG( ft_glyph_format_composite, 'c', 'o', 'm', 'p' ),
    FT_IMAGE_TAG( ft_glyph_format_bitmap,    'b', 'i', 't', 's' ),
    FT_IMAGE_TAG( ft_glyph_format_outline,   'o', 'u', 't', 'l' ),
    FT_IMAGE_TAG( ft_glyph_format_plotter,   '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.                                            */
  /*                                                                       */
  /*************************************************************************/


  /*************************************************************************/
  /*                                                                       */
  /* <Section>                                                             */
  /*    Raster                                                             */
  /*                                                                       */
  /* <Title>                                                               */
  /*    Scanline converter                                                 */
  /*                                                                       */
  /* <Abstract>                                                            */
  /*    How vectorial outlines are converted into bitmaps and pixmaps.     */
  /*                                                                       */
  /* <Description>                                                         */
  /*    This section contains technical definitions.                       */
  /*                                                                       */
  /*************************************************************************/


  /*************************************************************************/
  /*                                                                       */
  /* <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                                                     */