qgrayraster.c

奇趣公司比较新的qt/emd版本

/****************************************************************************
**
** This file is part of the QtGui module of the Qt Toolkit.
**
** This file contains third party code which is not governed by the Qt
** Commercial License Agreement. Please read the license headers below
** for more information.
** 
** Further information about Qt licensing is available at:
** http://www.trolltech.com/products/qt/licensing.html or by
** contacting [e-mail].
**
** This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
** WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
**
****************************************************************************/

/***************************************************************************/
/*                                                                         */
/*  qgrayraster.c, derived from ftgrays.c                                  */
/*                                                                         */
/*    A new `perfect' anti-aliasing renderer (body).                       */
/*                                                                         */
/*  Copyright 2000-2001, 2002, 2003 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, ../../3rdparty/freetype/docs/FTL.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 can be compiled without the rest of the FreeType engine, by */
  /* defining the _STANDALONE_ macro when compiling it.  You also need to  */
  /* put the files `ftgrays.h' and `ftimage.h' into the current            */
  /* compilation directory.  Typically, you could do something like        */
  /*                                                                       */
  /* - copy `src/smooth/ftgrays.c' (this file) to your current directory   */
  /*                                                                       */
  /* - copy `include/freetype/ftimage.h' and `src/smooth/ftgrays.h' to the */
  /*   same directory                                                      */
  /*                                                                       */
  /* - compile `ftgrays' with the _STANDALONE_ macro defined, as in        */
  /*                                                                       */
  /*     cc -c -D_STANDALONE_ ftgrays.c                                    */
  /*                                                                       */
  /* The renderer can be initialized with a call to                        */
  /* `qt_ft_gray_raster.raster_new'; an anti-aliased bitmap can be generated  */
  /* with a call to `qt_ft_gray_raster.raster_render'.                        */
  /*                                                                       */
  /* See the comments and documentation in the file `ftimage.h' for more   */
  /* details on how the raster works.                                      */
  /*                                                                       */
  /*************************************************************************/

  /*************************************************************************/
  /*                                                                       */
  /* This is a new anti-aliasing scan-converter for FreeType 2.  The       */
  /* algorithm used here is _very_ different from the one in the standard  */
  /* `ftraster' module.  Actually, `ftgrays' computes the _exact_          */
  /* coverage of the outline on each pixel cell.                           */
  /*                                                                       */
  /* It is based on ideas that I initially found in Raph Levien's          */
  /* excellent LibArt graphics library (see http://www.levien.com/libart   */
  /* for more information, though the web pages do not tell anything       */
  /* about the renderer; you'll have to dive into the source code to       */
  /* understand how it works).                                             */
  /*                                                                       */
  /* Note, however, that this is a _very_ different implementation         */
  /* compared to Raph's.  Coverage information is stored in a very         */
  /* different way, and I don't use sorted vector paths.  Also, it doesn't */
  /* use floating point values.                                            */
  /*                                                                       */
  /* This renderer has the following advantages:                           */
  /*                                                                       */
  /* - It doesn't need an intermediate bitmap.  Instead, one can supply a  */
  /*   callback function that will be called by the renderer to draw gray  */
  /*   spans on any target surface.  You can thus do direct composition on */
  /*   any kind of bitmap, provided that you give the renderer the right   */
  /*   callback.                                                           */
  /*                                                                       */
  /* - A perfect anti-aliaser, i.e., it computes the _exact_ coverage on   */
  /*   each pixel cell.                                                    */
  /*                                                                       */
  /* - It performs a single pass on the outline (the `standard' FT2        */
  /*   renderer makes two passes).                                         */
  /*                                                                       */
  /* - It can easily be modified to render to _any_ number of gray levels  */
  /*   cheaply.                                                            */
  /*                                                                       */
  /* - For small (< 20) pixel sizes, it is faster than the standard        */
  /*   renderer.                                                           */
  /*                                                                       */
  /*************************************************************************/

/* experimental support for gamma correction within the rasterizer */
#define xxxGRAYS_USE_GAMMA


  /*************************************************************************/
  /*                                                                       */
  /* The macro QT_FT_COMPONENT is used in trace mode.  It is an implicit      */
  /* parameter of the QT_FT_TRACE() and QT_FT_ERROR() macros, used to print/log  */
  /* messages during execution.                                            */
  /*                                                                       */
#undef  QT_FT_COMPONENT
#define QT_FT_COMPONENT  trace_smooth


#define ErrRaster_MemoryOverflow   -4


#include <string.h>             /* for qt_ft_memcpy() */
#include <setjmp.h>
#include <limits.h>
#define QT_FT_UINT_MAX  UINT_MAX

#define qt_ft_memset   memset

#define qt_ft_setjmp   setjmp
#define qt_ft_longjmp  longjmp
#define qt_ft_jmp_buf  jmp_buf


#define ErrRaster_Invalid_Mode     -2
#define ErrRaster_Invalid_Outline  -1

#define QT_FT_BEGIN_HEADER
#define QT_FT_END_HEADER

#include <private/qrasterdefs_p.h>
#include <private/qgrayraster_p.h>

#include <stdlib.h>
#include <stdio.h>

  /* This macro is used to indicate that a function parameter is unused. */
  /* Its purpose is simply to reduce compiler warnings.  Note also that  */
  /* simply defining it as `(void)x' doesn't avoid warnings with certain */
  /* ANSI compilers (e.g. LCC).                                          */
#define QT_FT_UNUSED( x )  (x) = (x)

  /* Disable the tracing mechanism for simplicity -- developers can      */
  /* activate it easily by redefining these two macros.                  */
#ifndef QT_FT_ERROR
#define QT_FT_ERROR( x )  do ; while ( 0 )     /* nothing */
#endif

#ifndef QT_FT_TRACE
#define QT_FT_TRACE( x )  do ; while ( 0 )     /* nothing */
#endif


#ifndef QT_FT_MEM_SET
#define QT_FT_MEM_SET( d, s, c )  qt_ft_memset( d, s, c )
#endif

#ifndef QT_FT_MEM_ZERO
#define QT_FT_MEM_ZERO( dest, count )  QT_FT_MEM_SET( dest, 0, count )
#endif

  /* define this to dump debugging information */
#define xxxDEBUG_GRAYS

  /* as usual, for the speed hungry :-) */

#define RAS_ARG   PRaster  raster
#define RAS_ARG_  PRaster  raster,

#define RAS_VAR   raster
#define RAS_VAR_  raster,

#define ras       (*raster)



  /* must be at least 6 bits! */
#define PIXEL_BITS  8

#define ONE_PIXEL       ( 1L << PIXEL_BITS )
#define PIXEL_MASK      ( -1L << PIXEL_BITS )
#define TRUNC( x )      ( (TCoord)((x) >> PIXEL_BITS) )
#define SUBPIXELS( x )  ( (TPos)(x) << PIXEL_BITS )
#define FLOOR( x )      ( (x) & -ONE_PIXEL )
#define CEILING( x )    ( ( (x) + ONE_PIXEL - 1 ) & -ONE_PIXEL )
#define ROUND( x )      ( ( (x) + ONE_PIXEL / 2 ) & -ONE_PIXEL )

#if PIXEL_BITS >= 6
#define UPSCALE( x )    ( (x) << ( PIXEL_BITS - 6 ) )
#define DOWNSCALE( x )  ( (x) >> ( PIXEL_BITS - 6 ) )
#else
#define UPSCALE( x )    ( (x) >> ( 6 - PIXEL_BITS ) )
#define DOWNSCALE( x )  ( (x) << ( 6 - PIXEL_BITS ) )
#endif

  /* Define this if you want to use a more compact storage scheme.  This   */
  /* increases the number of cells available in the render pool but slows  */
  /* down the rendering a bit.  It is useful if you have a really tiny     */
  /* render pool.                                                          */
#undef GRAYS_COMPACT


  /*************************************************************************/
  /*                                                                       */
  /*   TYPE DEFINITIONS                                                    */
  /*                                                                       */

  /* don't change the following types to QT_FT_Int or QT_FT_Pos, since we might */
  /* need to define them to "float" or "double" when experimenting with   */
  /* new algorithms                                                       */

  typedef int   TCoord;   /* integer scanline/pixel coordinate */
  typedef long  TPos;     /* sub-pixel coordinate              */

  /* determine the type used to store cell areas.  This normally takes at */
  /* least PIXEL_BYTES*2 + 1.  On 16-bit systems, we need to use `long'   */
  /* instead of `int', otherwise bad things happen                        */

#if PIXEL_BITS <= 7

  typedef int   TArea;

#else /* PIXEL_BITS >= 8 */

  /* approximately determine the size of integers using an ANSI-C header */
#if QT_FT_UINT_MAX == 0xFFFFU
  typedef long  TArea;
#else
  typedef int  TArea;
#endif

#endif /* PIXEL_BITS >= 8 */


  /* maximal number of gray spans in a call to the span callback */
#define QT_FT_MAX_GRAY_SPANS  256


#ifdef GRAYS_COMPACT

  typedef struct  TCell_
  {
    short  x     : 14;
    short  y     : 14;
    int    cover : PIXEL_BITS + 2;
    int    area  : PIXEL_BITS * 2 + 2;

  } TCell, *PCell;

#else /* GRAYS_COMPACT */

  typedef struct  TCell_
  {
    TCoord  x;
    TCoord  y;
    int     cover;
    TArea   area;

  } TCell, *PCell;

#endif /* GRAYS_COMPACT */


  typedef struct  TRaster_
  {
    PCell   cells;
    int     max_cells;
    int     num_cells;

    TPos    min_ex, max_ex;
    TPos    min_ey, max_ey;

    TArea   area;
    int     cover;
    int     invalid;

    TCoord  ex, ey;
    TCoord  cx, cy;
    TPos    x,  y;

    TPos    last_ey;

    QT_FT_Vector   bez_stack[32 * 3 + 1];
    int         lev_stack[32];

    QT_FT_Outline  outline;
    QT_FT_Bitmap   target;
    QT_FT_BBox     clip_box;

    QT_FT_Span     gray_spans[QT_FT_MAX_GRAY_SPANS];
    int         num_gray_spans;

    QT_FT_Raster_Span_Func  render_span;
    void*                render_span_data;

    int  band_size;
    int  band_shoot;
    int  conic_level;
    int  cubic_level;

    void*       memory;
    qt_ft_jmp_buf  jump_buffer;

#ifdef GRAYS_USE_GAMMA
    unsigned char  gamma[257];
#endif

  } TRaster, *PRaster;


  /*************************************************************************/
  /*                                                                       */
  /* Initialize the cells table.                                           */
  /*                                                                       */
  static void
  gray_init_cells( RAS_ARG_ void*  buffer,
                   long            byte_size )
  {
    ras.cells     = (PCell)buffer;
    ras.max_cells = (int)( byte_size / sizeof ( TCell ) );
    ras.num_cells = 0;
    ras.area      = 0;
    ras.cover     = 0;
    ras.invalid   = 1;
  }


  /*************************************************************************/
  /*                                                                       */
  /* Compute the outline bounding box.                                     */
  /*                                                                       */
  static void
  gray_compute_cbox( RAS_ARG )
  {
    QT_FT_Outline*  outline = &ras.outline;
    QT_FT_Vector*   vec     = outline->points;
    QT_FT_Vector*   limit   = vec + outline->n_points;


    if ( outline->n_points <= 0 )
    {
      ras.min_ex = ras.max_ex = 0;
      ras.min_ey = ras.max_ey = 0;
      return;
    }

    ras.min_ex = ras.max_ex = vec->x;
    ras.min_ey = ras.max_ey = vec->y;

    vec++;

    for ( ; vec < limit; vec++ )
    {
      TPos  x = vec->x;
      TPos  y = vec->y;


      if ( x < ras.min_ex ) ras.min_ex = x;
      if ( x > ras.max_ex ) ras.max_ex = x;
      if ( y < ras.min_ey ) ras.min_ey = y;
      if ( y > ras.max_ey ) ras.max_ey = y;
    }

    /* truncate the bounding box to integer pixels */
    ras.min_ex = ras.min_ex >> 6;
    ras.min_ey = ras.min_ey >> 6;
    ras.max_ex = ( ras.max_ex + 63 ) >> 6;
    ras.max_ey = ( ras.max_ey + 63 ) >> 6;
  }


  /*************************************************************************/
  /*                                                                       */
  /* Record the current cell in the table.                                 */
  /*                                                                       */
  static void
  gray_record_cell( RAS_ARG )
  {
    PCell  cell;


    if ( !ras.invalid && ( ras.area | ras.cover ) )
    {
      if ( ras.num_cells >= ras.max_cells )
        qt_ft_longjmp( ras.jump_buffer, 1 );

      cell        = ras.cells + ras.num_cells++;
      cell->x     = (TCoord)(ras.ex - ras.min_ex);
      cell->y     = (TCoord)(ras.ey - ras.min_ey);
      cell->area  = ras.area;
      cell->cover = ras.cover;
    }
  }


  /*************************************************************************/
  /*                                                                       */
  /* Set the current cell to a new position.                               */
  /*                                                                       */
  static void
  gray_set_cell( RAS_ARG_ TCoord  ex,
                          TCoord  ey )
  {
    int  invalid, record, clean;


    /* Move the cell pointer to a new position.  We set the `invalid'      */
    /* flag to indicate that the cell isn't part of those we're interested */
    /* in during the render phase.  This means that:                       */
    /*                                                                     */
    /* . the new vertical position must be within min_ey..max_ey-1.        */
    /* . the new horizontal position must be strictly less than max_ex     */
    /*                                                                     */
    /* Note that if a cell is to the left of the clipping region, it is    */
    /* actually set to the (min_ex-1) horizontal position.                 */

    record  = 0;
    clean   = 1;

    invalid = ( ey < ras.min_ey || ey >= ras.max_ey || ex >= ras.max_ex );
    if ( !invalid )
    {
      /* All cells that are on the left of the clipping region go to the */
      /* min_ex - 1 horizontal position.                                 */
      if ( ex < ras.min_ex )
        ex = (TCoord)(ras.min_ex - 1);

      /* if our position is new, then record the previous cell */
      if ( ex != ras.ex || ey != ras.ey )
        record = 1;
      else
        clean = ras.invalid;  /* do not clean if we didn't move from */
                              /* a valid cell                        */
    }

    /* record the previous cell if needed (i.e., if we changed the cell */
    /* position, of changed the `invalid' flag)                         */
    if ( ras.invalid != invalid || record )
      gray_record_cell( RAS_VAR );

    if ( clean )
    {
      ras.area  = 0;
      ras.cover = 0;
    }

    ras.invalid = invalid;
    ras.ex      = ex;
    ras.ey      = ey;
  }


  /*************************************************************************/
  /*                                                                       */
  /* Start a new contour at a given cell.                                  */
  /*                                                                       */
  static void
  gray_start_cell( RAS_ARG_  TCoord  ex,
                             TCoord  ey )
  {
    if ( ex < ras.min_ex )
      ex = (TCoord)(ras.min_ex - 1);

    ras.area    = 0;
    ras.cover   = 0;
    ras.ex      = ex;
    ras.ey      = ey;
    ras.last_ey = SUBPIXELS( ey );
    ras.invalid = 0;

    gray_set_cell( RAS_VAR_ ex, ey );
  }


  /*************************************************************************/
  /*                                                                       */
  /* Render a scanline as one or more cells.                               */
  /*                                                                       */
  static void
  gray_render_scanline( RAS_ARG_  TCoord  ey,
                                  TPos    x1,
                                  TCoord  y1,
                                  TPos    x2,
                                  TCoord  y2 )
  {
    TCoord  ex1, ex2, fx1, fx2, delta;
    long    p, first, dx;
    int     incr, lift, mod, rem;


    dx = x2 - x1;

    ex1 = TRUNC( x1 ); /* if (ex1 >= ras.max_ex) ex1 = ras.max_ex-1; */
    ex2 = TRUNC( x2 ); /* if (ex2 >= ras.max_ex) ex2 = ras.max_ex-1; */
    fx1 = (TCoord)( x1 - SUBPIXELS( ex1 ) );
    fx2 = (TCoord)( x2 - SUBPIXELS( ex2 ) );

    /* trivial case.  Happens often */
    if ( y1 == y2 )
    {
      gray_set_cell( RAS_VAR_ ex2, ey );
      return;
    }

    /* everything is located in a single cell.  That is easy! */
    /*                                                        */
    if ( ex1 == ex2 )
    {
      delta      = y2 - y1;
      ras.area  += (TArea)( fx1 + fx2 ) * delta;
      ras.cover += delta;
      return;
    }

    /* ok, we'll have to render a run of adjacent cells on the same */
    /* scanline...                                                  */
    /*                                                              */
    p     = ( ONE_PIXEL - fx1 ) * ( y2 - y1 );
    first = ONE_PIXEL;