1  /****************************************************************************
       2   *
       3   * ftsdfcommon.h
       4   *
       5   *   Auxiliary data for Signed Distance Field support (specification).
       6   *
       7   * Copyright (C) 2020-2023 by
       8   * David Turner, Robert Wilhelm, and Werner Lemberg.
       9   *
      10   * Written by Anuj Verma.
      11   *
      12   * This file is part of the FreeType project, and may only be used,
      13   * modified, and distributed under the terms of the FreeType project
      14   * license, LICENSE.TXT.  By continuing to use, modify, or distribute
      15   * this file you indicate that you have read the license and
      16   * understand and accept it fully.
      17   *
      18   */
      19  
      20  
      21    /****************************************************
      22     *
      23     * This file contains common functions and properties
      24     * for both the 'sdf' and 'bsdf' renderers.
      25     *
      26     */
      27  
      28  #ifndef FTSDFCOMMON_H_
      29  #define FTSDFCOMMON_H_
      30  
      31  #include <ft2build.h>
      32  #include FT_CONFIG_CONFIG_H
      33  #include <freetype/internal/ftobjs.h>
      34  
      35  
      36  FT_BEGIN_HEADER
      37  
      38  
      39    /**************************************************************************
      40     *
      41     * default values (cannot be set individually for each renderer)
      42     *
      43     */
      44  
      45    /* default spread value */
      46  #define DEFAULT_SPREAD  8
      47    /* minimum spread supported by the renderer */
      48  #define MIN_SPREAD      2
      49    /* maximum spread supported by the renderer */
      50  #define MAX_SPREAD      32
      51    /* pixel size in 26.6 */
      52  #define ONE_PIXEL       ( 1 << 6 )
      53  
      54  
      55    /**************************************************************************
      56     *
      57     * common definitions (cannot be set individually for each renderer)
      58     *
      59     */
      60  
      61    /* If this macro is set to 1 the rasterizer uses squared distances for */
      62    /* computation.  It can greatly improve the performance but there is a */
      63    /* chance of overflow and artifacts.  You can safely use it up to a    */
      64    /* pixel size of 128.                                                  */
      65  #ifndef USE_SQUARED_DISTANCES
      66  #define USE_SQUARED_DISTANCES  0
      67  #endif
      68  
      69  
      70    /**************************************************************************
      71     *
      72     * common macros
      73     *
      74     */
      75  
      76    /* convert int to 26.6 fixed-point   */
      77  #define FT_INT_26D6( x )   ( x * 64 )
      78    /* convert int to 16.16 fixed-point  */
      79  #define FT_INT_16D16( x )  ( x * 65536 )
      80    /* convert 26.6 to 16.16 fixed-point */
      81  #define FT_26D6_16D16( x ) ( x * 1024 )
      82  
      83  
      84    /* Convenience macro to call a function; it  */
      85    /* jumps to label `Exit` if an error occurs. */
      86  #define FT_CALL( x ) do                          \
      87                       {                           \
      88                         error = ( x );            \
      89                         if ( error != FT_Err_Ok ) \
      90                           goto Exit;              \
      91                       } while ( 0 )
      92  
      93  
      94    /*
      95     * The macro `VECTOR_LENGTH_16D16` computes either squared distances or
      96     * actual distances, depending on the value of `USE_SQUARED_DISTANCES`.
      97     *
      98     * By using squared distances the performance can be greatly improved but
      99     * there is a risk of overflow.
     100     */
     101  #if USE_SQUARED_DISTANCES
     102  #define VECTOR_LENGTH_16D16( v )  ( FT_MulFix( v.x, v.x ) + \
     103                                      FT_MulFix( v.y, v.y ) )
     104  #else
     105  #define VECTOR_LENGTH_16D16( v )  FT_Vector_Length( &v )
     106  #endif
     107  
     108  
     109    /**************************************************************************
     110     *
     111     * common typedefs
     112     *
     113     */
     114  
     115    typedef FT_Vector FT_26D6_Vec;   /* with 26.6 fixed-point components  */
     116    typedef FT_Vector FT_16D16_Vec;  /* with 16.16 fixed-point components */
     117  
     118    typedef FT_Int32  FT_16D16;      /* 16.16 fixed-point representation  */
     119    typedef FT_Int32  FT_26D6;       /* 26.6 fixed-point representation   */
     120    typedef FT_Byte   FT_SDFFormat;  /* format to represent SDF data      */
     121  
     122    typedef FT_BBox   FT_CBox;       /* control box of a curve            */
     123  
     124  
     125    FT_LOCAL( FT_16D16 )
     126    square_root( FT_16D16  val );
     127  
     128    FT_LOCAL( FT_SDFFormat )
     129    map_fixed_to_sdf( FT_16D16  dist,
     130                      FT_16D16  max_value );
     131  
     132    FT_LOCAL( FT_SDFFormat )
     133    invert_sign( FT_SDFFormat  dist );
     134  
     135  
     136  FT_END_HEADER
     137  
     138  #endif /* FTSDFCOMMON_H_ */
     139  
     140  
     141  /* END */