ftglyph.h

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/****************************************************************************
 *
 * ftglyph.h
 *
 *   FreeType convenience functions to handle glyphs (specification).
 *
 * Copyright (C) 1996-2019 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.
 *
 */
 
 
  /**************************************************************************
   *
   * This file contains the definition of several convenience functions that
   * can be used by client applications to easily retrieve glyph bitmaps and
   * outlines from a given face.
   *
   * These functions should be optional if you are writing a font server or
   * text layout engine on top of FreeType.  However, they are pretty handy
   * for many other simple uses of the library.
   *
   */
 
 
#ifndef FTGLYPH_H_
#define FTGLYPH_H_
 
 
#include <ft2build.h>
#include FT_FREETYPE_H
 
#ifdef FREETYPE_H
#error "freetype.h of FreeType 1 has been loaded!"
#error "Please fix the directory search order for header files"
#error "so that freetype.h of FreeType 2 is found first."
#endif
 
 
FT_BEGIN_HEADER
 
 
  /**************************************************************************
   *
   * @section:
   *   glyph_management
   *
   * @title:
   *   Glyph Management
   *
   * @abstract:
   *   Generic interface to manage individual glyph data.
   *
   * @description:
   *   This section contains definitions used to manage glyph data through
   *   generic @FT_Glyph objects.  Each of them can contain a bitmap,
   *   a vector outline, or even images in other formats.  These objects are
   *   detached from @FT_Face, contrary to @FT_GlyphSlot.
   *
   */
 
 
  /* forward declaration to a private type */
  typedef struct FT_Glyph_Class_  FT_Glyph_Class;
 
 
  /**************************************************************************
   *
   * @type:
   *   FT_Glyph
   *
   * @description:
   *   Handle to an object used to model generic glyph images.  It is a
   *   pointer to the @FT_GlyphRec structure and can contain a glyph bitmap
   *   or pointer.
   *
   * @note:
   *   Glyph objects are not owned by the library.  You must thus release
   *   them manually (through @FT_Done_Glyph) _before_ calling
   *   @FT_Done_FreeType.
   */
  typedef struct FT_GlyphRec_*  FT_Glyph;
 
 
  /**************************************************************************
   *
   * @struct:
   *   FT_GlyphRec
   *
   * @description:
   *   The root glyph structure contains a given glyph image plus its advance
   *   width in 16.16 fixed-point format.
   *
   * @fields:
   *   library ::
   *     A handle to the FreeType library object.
   *
   *   clazz ::
   *     A pointer to the glyph's class.  Private.
   *
   *   format ::
   *     The format of the glyph's image.
   *
   *   advance ::
   *     A 16.16 vector that gives the glyph's advance width.
   */
  typedef struct  FT_GlyphRec_
  {
    FT_Library             library;
    const FT_Glyph_Class*  clazz;
    FT_Glyph_Format        format;
    FT_Vector              advance;
 
  } FT_GlyphRec;
 
 
  /**************************************************************************
   *
   * @type:
   *   FT_BitmapGlyph
   *
   * @description:
   *   A handle to an object used to model a bitmap glyph image.  This is a
   *   sub-class of @FT_Glyph, and a pointer to @FT_BitmapGlyphRec.
   */
  typedef struct FT_BitmapGlyphRec_*  FT_BitmapGlyph;
 
 
  /**************************************************************************
   *
   * @struct:
   *   FT_BitmapGlyphRec
   *
   * @description:
   *   A structure used for bitmap glyph images.  This really is a
   *   'sub-class' of @FT_GlyphRec.
   *
   * @fields:
   *   root ::
   *     The root @FT_Glyph fields.
   *
   *   left ::
   *     The left-side bearing, i.e., the horizontal distance from the
   *     current pen position to the left border of the glyph bitmap.
   *
   *   top ::
   *     The top-side bearing, i.e., the vertical distance from the current
   *     pen position to the top border of the glyph bitmap.  This distance
   *     is positive for upwards~y!
   *
   *   bitmap ::
   *     A descriptor for the bitmap.
   *
   * @note:
   *   You can typecast an @FT_Glyph to @FT_BitmapGlyph if you have
   *   `glyph->format == FT_GLYPH_FORMAT_BITMAP`.  This lets you access the
   *   bitmap's contents easily.
   *
   *   The corresponding pixel buffer is always owned by @FT_BitmapGlyph and
   *   is thus created and destroyed with it.
   */
  typedef struct  FT_BitmapGlyphRec_
  {
    FT_GlyphRec  root;
    FT_Int       left;
    FT_Int       top;
    FT_Bitmap    bitmap;
 
  } FT_BitmapGlyphRec;
 
 
  /**************************************************************************
   *
   * @type:
   *   FT_OutlineGlyph
   *
   * @description:
   *   A handle to an object used to model an outline glyph image.  This is a
   *   sub-class of @FT_Glyph, and a pointer to @FT_OutlineGlyphRec.
   */
  typedef struct FT_OutlineGlyphRec_*  FT_OutlineGlyph;
 
 
  /**************************************************************************
   *
   * @struct:
   *   FT_OutlineGlyphRec
   *
   * @description:
   *   A structure used for outline (vectorial) glyph images.  This really is
   *   a 'sub-class' of @FT_GlyphRec.
   *
   * @fields:
   *   root ::
   *     The root @FT_Glyph fields.
   *
   *   outline ::
   *     A descriptor for the outline.
   *
   * @note:
   *   You can typecast an @FT_Glyph to @FT_OutlineGlyph if you have
   *   `glyph->format == FT_GLYPH_FORMAT_OUTLINE`.  This lets you access the
   *   outline's content easily.
   *
   *   As the outline is extracted from a glyph slot, its coordinates are
   *   expressed normally in 26.6 pixels, unless the flag @FT_LOAD_NO_SCALE
   *   was used in @FT_Load_Glyph() or @FT_Load_Char().
   *
   *   The outline's tables are always owned by the object and are destroyed
   *   with it.
   */
  typedef struct  FT_OutlineGlyphRec_
  {
    FT_GlyphRec  root;
    FT_Outline   outline;
 
  } FT_OutlineGlyphRec;
 
 
  /**************************************************************************
   *
   * @function:
   *   FT_New_Glyph
   *
   * @description:
   *   A function used to create a new empty glyph image.  Note that the
   *   created @FT_Glyph object must be released with @FT_Done_Glyph.
   *
   * @input:
   *   library ::
   *     A handle to the FreeType library object.
   *
   *   format ::
   *     The format of the glyph's image.
   *
   * @output:
   *   aglyph ::
   *     A handle to the glyph object.
   *
   * @return:
   *   FreeType error code.  0~means success.
   *
   * @since:
   *   2.10
   */
  FT_EXPORT( FT_Error )
  FT_New_Glyph( FT_Library       library,
                FT_Glyph_Format  format,
                FT_Glyph         *aglyph );
 
 
  /**************************************************************************
   *
   * @function:
   *   FT_Get_Glyph
   *
   * @description:
   *   A function used to extract a glyph image from a slot.  Note that the
   *   created @FT_Glyph object must be released with @FT_Done_Glyph.
   *
   * @input:
   *   slot ::
   *     A handle to the source glyph slot.
   *
   * @output:
   *   aglyph ::
   *     A handle to the glyph object.
   *
   * @return:
   *   FreeType error code.  0~means success.
   *
   * @note:
   *   Because `*aglyph->advance.x` and `*aglyph->advance.y` are 16.16
   *   fixed-point numbers, `slot->advance.x` and `slot->advance.y` (which
   *   are in 26.6 fixed-point format) must be in the range ]-32768;32768[.
   */
  FT_EXPORT( FT_Error )
  FT_Get_Glyph( FT_GlyphSlot  slot,
                FT_Glyph     *aglyph );
 
 
  /**************************************************************************
   *
   * @function:
   *   FT_Glyph_Copy
   *
   * @description:
   *   A function used to copy a glyph image.  Note that the created
   *   @FT_Glyph object must be released with @FT_Done_Glyph.
   *
   * @input:
   *   source ::
   *     A handle to the source glyph object.
   *
   * @output:
   *   target ::
   *     A handle to the target glyph object.  0~in case of error.
   *
   * @return:
   *   FreeType error code.  0~means success.
   */
  FT_EXPORT( FT_Error )
  FT_Glyph_Copy( FT_Glyph   source,
                 FT_Glyph  *target );
 
 
  /**************************************************************************
   *
   * @function:
   *   FT_Glyph_Transform
   *
   * @description:
   *   Transform a glyph image if its format is scalable.
   *
   * @inout:
   *   glyph ::
   *     A handle to the target glyph object.
   *
   * @input:
   *   matrix ::
   *     A pointer to a 2x2 matrix to apply.
   *
   *   delta ::
   *     A pointer to a 2d vector to apply.  Coordinates are expressed in
   *     1/64th of a pixel.
   *
   * @return:
   *   FreeType error code (if not 0, the glyph format is not scalable).
   *
   * @note:
   *   The 2x2 transformation matrix is also applied to the glyph's advance
   *   vector.
   */
  FT_EXPORT( FT_Error )
  FT_Glyph_Transform( FT_Glyph    glyph,
                      FT_Matrix*  matrix,
                      FT_Vector*  delta );
 
 
  /**************************************************************************
   *
   * @enum:
   *   FT_Glyph_BBox_Mode
   *
   * @description:
   *   The mode how the values of @FT_Glyph_Get_CBox are returned.
   *
   * @values:
   *   FT_GLYPH_BBOX_UNSCALED ::
   *     Return unscaled font units.
   *
   *   FT_GLYPH_BBOX_SUBPIXELS ::
   *     Return unfitted 26.6 coordinates.
   *
   *   FT_GLYPH_BBOX_GRIDFIT ::
   *     Return grid-fitted 26.6 coordinates.
   *
   *   FT_GLYPH_BBOX_TRUNCATE ::
   *     Return coordinates in integer pixels.
   *
   *   FT_GLYPH_BBOX_PIXELS ::
   *     Return grid-fitted pixel coordinates.
   */
  typedef enum  FT_Glyph_BBox_Mode_
  {
    FT_GLYPH_BBOX_UNSCALED  = 0,
    FT_GLYPH_BBOX_SUBPIXELS = 0,
    FT_GLYPH_BBOX_GRIDFIT   = 1,
    FT_GLYPH_BBOX_TRUNCATE  = 2,
    FT_GLYPH_BBOX_PIXELS    = 3
 
  } FT_Glyph_BBox_Mode;
 
 
  /* these constants are deprecated; use the corresponding */
  /* `FT_Glyph_BBox_Mode` values instead                   */
#define ft_glyph_bbox_unscaled   FT_GLYPH_BBOX_UNSCALED
#define ft_glyph_bbox_subpixels  FT_GLYPH_BBOX_SUBPIXELS
#define ft_glyph_bbox_gridfit    FT_GLYPH_BBOX_GRIDFIT
#define ft_glyph_bbox_truncate   FT_GLYPH_BBOX_TRUNCATE
#define ft_glyph_bbox_pixels     FT_GLYPH_BBOX_PIXELS
 
 
  /**************************************************************************
   *
   * @function:
   *   FT_Glyph_Get_CBox
   *
   * @description:
   *   Return a glyph's 'control box'.  The control box encloses all the
   *   outline's points, including Bezier 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 that
   *   contains Bezier 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.
   *
   * @input:
   *   glyph ::
   *     A handle to the source glyph object.
   *
   *   mode ::
   *     The mode that indicates how to interpret the returned bounding box
   *     values.
   *
   * @output:
   *   acbox ::
   *     The glyph coordinate bounding box.  Coordinates are expressed in
   *     1/64th of pixels if it is grid-fitted.
   *
   * @note:
   *   Coordinates are relative to the glyph origin, using the y~upwards
   *   convention.
   *
   *   If the glyph has been loaded with @FT_LOAD_NO_SCALE, `bbox_mode` must
   *   be set to @FT_GLYPH_BBOX_UNSCALED to get unscaled font units in 26.6
   *   pixel format.  The value @FT_GLYPH_BBOX_SUBPIXELS is another name for
   *   this constant.
   *
   *   If the font is tricky and the glyph has been loaded with
   *   @FT_LOAD_NO_SCALE, the resulting CBox is meaningless.  To get
   *   reasonable values for the CBox 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 CBox, which can be
   *   eventually converted back to font units.
   *
   *   Note that the maximum coordinates are exclusive, which means that one
   *   can compute the width and height of the glyph image (be it in integer
   *   or 26.6 pixels) as:
   *
   *   ```
   *     width  = bbox.xMax - bbox.xMin;
   *     height = bbox.yMax - bbox.yMin;
   *   ```
   *
   *   Note also that for 26.6 coordinates, if `bbox_mode` is set to
   *   @FT_GLYPH_BBOX_GRIDFIT, the coordinates will also be grid-fitted,
   *   which corresponds to:
   *
   *   ```
   *     bbox.xMin = FLOOR(bbox.xMin);
   *     bbox.yMin = FLOOR(bbox.yMin);
   *     bbox.xMax = CEILING(bbox.xMax);
   *     bbox.yMax = CEILING(bbox.yMax);
   *   ```
   *
   *   To get the bbox in pixel coordinates, set `bbox_mode` to
   *   @FT_GLYPH_BBOX_TRUNCATE.
   *
   *   To get the bbox in grid-fitted pixel coordinates, set `bbox_mode` to
   *   @FT_GLYPH_BBOX_PIXELS.
   */
  FT_EXPORT( void )
  FT_Glyph_Get_CBox( FT_Glyph  glyph,
                     FT_UInt   bbox_mode,
                     FT_BBox  *acbox );
 
 
  /**************************************************************************
   *
   * @function:
   *   FT_Glyph_To_Bitmap
   *
   * @description:
   *   Convert a given glyph object to a bitmap glyph object.
   *
   * @inout:
   *   the_glyph ::
   *     A pointer to a handle to the target glyph.
   *
   * @input:
   *   render_mode ::
   *     An enumeration that describes how the data is rendered.
   *
   *   origin ::
   *     A pointer to a vector used to translate the glyph image before
   *     rendering.  Can be~0 (if no translation).  The origin is expressed
   *     in 26.6 pixels.
   *
   *   destroy ::
   *     A boolean that indicates that the original glyph image should be
   *     destroyed by this function.  It is never destroyed in case of error.
   *
   * @return:
   *   FreeType error code.  0~means success.
   *
   * @note:
   *   This function does nothing if the glyph format isn't scalable.
   *
   *   The glyph image is translated with the `origin` vector before
   *   rendering.
   *
   *   The first parameter is a pointer to an @FT_Glyph handle, that will be
   *   _replaced_ by this function (with newly allocated data).  Typically,
   *   you would use (omitting error handling):
   *
   *   ```
   *     FT_Glyph        glyph;
   *     FT_BitmapGlyph  glyph_bitmap;
   *
   *
   *     // load glyph
   *     error = FT_Load_Char( face, glyph_index, FT_LOAD_DEFAULT );
   *
   *     // extract glyph image
   *     error = FT_Get_Glyph( face->glyph, &glyph );
   *
   *     // convert to a bitmap (default render mode + destroying old)
   *     if ( glyph->format != FT_GLYPH_FORMAT_BITMAP )
   *     {
   *       error = FT_Glyph_To_Bitmap( &glyph, FT_RENDER_MODE_NORMAL,
   *                                     0, 1 );
   *       if ( error ) // `glyph' unchanged
   *         ...
   *     }
   *
   *     // access bitmap content by typecasting
   *     glyph_bitmap = (FT_BitmapGlyph)glyph;
   *
   *     // do funny stuff with it, like blitting/drawing
   *     ...
   *
   *     // discard glyph image (bitmap or not)
   *     FT_Done_Glyph( glyph );
   *   ```
   *
   *   Here is another example, again without error handling:
   *
   *   ```
   *     FT_Glyph  glyphs[MAX_GLYPHS]
   *
   *
   *     ...
   *
   *     for ( idx = 0; i < MAX_GLYPHS; i++ )
   *       error = FT_Load_Glyph( face, idx, FT_LOAD_DEFAULT ) ||
   *               FT_Get_Glyph ( face->glyph, &glyphs[idx] );
   *
   *     ...
   *
   *     for ( idx = 0; i < MAX_GLYPHS; i++ )
   *     {
   *       FT_Glyph  bitmap = glyphs[idx];
   *
   *
   *       ...
   *
   *       // after this call, `bitmap' no longer points into
   *       // the `glyphs' array (and the old value isn't destroyed)
   *       FT_Glyph_To_Bitmap( &bitmap, FT_RENDER_MODE_MONO, 0, 0 );
   *
   *       ...
   *
   *       FT_Done_Glyph( bitmap );
   *     }
   *
   *     ...
   *
   *     for ( idx = 0; i < MAX_GLYPHS; i++ )
   *       FT_Done_Glyph( glyphs[idx] );
   *   ```
   */
  FT_EXPORT( FT_Error )
  FT_Glyph_To_Bitmap( FT_Glyph*       the_glyph,
                      FT_Render_Mode  render_mode,
                      FT_Vector*      origin,
                      FT_Bool         destroy );
 
 
  /**************************************************************************
   *
   * @function:
   *   FT_Done_Glyph
   *
   * @description:
   *   Destroy a given glyph.
   *
   * @input:
   *   glyph ::
   *     A handle to the target glyph object.
   */
  FT_EXPORT( void )
  FT_Done_Glyph( FT_Glyph  glyph );
 
  /* */
 
 
  /* other helpful functions */
 
  /**************************************************************************
   *
   * @section:
   *   computations
   *
   */
 
 
  /**************************************************************************
   *
   * @function:
   *   FT_Matrix_Multiply
   *
   * @description:
   *   Perform the matrix operation `b = a*b`.
   *
   * @input:
   *   a ::
   *     A pointer to matrix `a`.
   *
   * @inout:
   *   b ::
   *     A pointer to matrix `b`.
   *
   * @note:
   *   The result is undefined if either `a` or `b` is zero.
   *
   *   Since the function uses wrap-around arithmetic, results become
   *   meaningless if the arguments are very large.
   */
  FT_EXPORT( void )
  FT_Matrix_Multiply( const FT_Matrix*  a,
                      FT_Matrix*        b );
 
 
  /**************************************************************************
   *
   * @function:
   *   FT_Matrix_Invert
   *
   * @description:
   *   Invert a 2x2 matrix.  Return an error if it can't be inverted.
   *
   * @inout:
   *   matrix ::
   *     A pointer to the target matrix.  Remains untouched in case of error.
   *
   * @return:
   *   FreeType error code.  0~means success.
   */
  FT_EXPORT( FT_Error )
  FT_Matrix_Invert( FT_Matrix*  matrix );
 
  /* */
 
 
FT_END_HEADER
 
#endif /* FTGLYPH_H_ */
 
 
/* END */
 
 
/* Local Variables: */
/* coding: utf-8    */
/* End:             */