chromium/third_party/freetype/src/src/base/ftlcdfil.c

/****************************************************************************
 *
 * ftlcdfil.c
 *
 *   FreeType API for color filtering of subpixel bitmap glyphs (body).
 *
 * Copyright (C) 2006-2024 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.
 *
 */


#include <freetype/internal/ftdebug.h>

#include <freetype/ftlcdfil.h>
#include <freetype/ftimage.h>
#include <freetype/internal/ftobjs.h>


#ifdef FT_CONFIG_OPTION_SUBPIXEL_RENDERING

/* define USE_LEGACY to implement the legacy filter */
#define USE_LEGACY

#define FT_SHIFTCLAMP( x ) …


  /* add padding according to filter weights */
  FT_BASE_DEF( void )
  ft_lcd_padding( FT_BBox*        cbox,
                  FT_GlyphSlot    slot,
                  FT_Render_Mode  mode )
  { … }


  /* FIR filter used by the default and light filters */
  FT_BASE_DEF( void )
  ft_lcd_filter_fir( FT_Bitmap*           bitmap,
                     FT_LcdFiveTapFilter  weights )
  { … }


#ifdef USE_LEGACY

  /* intra-pixel filter used by the legacy filter */
  static void
  _ft_lcd_filter_legacy( FT_Bitmap*      bitmap,
                         FT_Byte*        weights )
  { … }

#endif /* USE_LEGACY */


  /* documentation in ftlcdfil.h */

  FT_EXPORT_DEF( FT_Error )
  FT_Library_SetLcdFilterWeights( FT_Library      library,
                                  unsigned char  *weights )
  { … }


  /* documentation in ftlcdfil.h */

  FT_EXPORT_DEF( FT_Error )
  FT_Library_SetLcdFilter( FT_Library    library,
                           FT_LcdFilter  filter )
  { … }


  FT_EXPORT_DEF( FT_Error )
  FT_Library_SetLcdGeometry( FT_Library  library,
                             FT_Vector   sub[3] )
  { … }

#else /* !FT_CONFIG_OPTION_SUBPIXEL_RENDERING */

  /* add padding to accommodate outline shifts */
  FT_BASE_DEF( void )
  ft_lcd_padding( FT_BBox*        cbox,
                  FT_GlyphSlot    slot,
                  FT_Render_Mode  mode )
  {
    FT_Vector*  sub = slot->library->lcd_geometry;

    if ( mode == FT_RENDER_MODE_LCD )
    {
      cbox->xMin -= FT_MAX( FT_MAX( sub[0].x, sub[1].x ), sub[2].x );
      cbox->xMax -= FT_MIN( FT_MIN( sub[0].x, sub[1].x ), sub[2].x );
      cbox->yMin -= FT_MAX( FT_MAX( sub[0].y, sub[1].y ), sub[2].y );
      cbox->yMax -= FT_MIN( FT_MIN( sub[0].y, sub[1].y ), sub[2].y );
    }
    else if ( mode == FT_RENDER_MODE_LCD_V )
    {
      cbox->xMin -= FT_MAX( FT_MAX( sub[0].y, sub[1].y ), sub[2].y );
      cbox->xMax -= FT_MIN( FT_MIN( sub[0].y, sub[1].y ), sub[2].y );
      cbox->yMin += FT_MIN( FT_MIN( sub[0].x, sub[1].x ), sub[2].x );
      cbox->yMax += FT_MAX( FT_MAX( sub[0].x, sub[1].x ), sub[2].x );
    }
  }


  FT_EXPORT_DEF( FT_Error )
  FT_Library_SetLcdFilterWeights( FT_Library      library,
                                  unsigned char  *weights )
  {
    FT_UNUSED( library );
    FT_UNUSED( weights );

    return FT_THROW( Unimplemented_Feature );
  }


  FT_EXPORT_DEF( FT_Error )
  FT_Library_SetLcdFilter( FT_Library    library,
                           FT_LcdFilter  filter )
  {
    FT_UNUSED( library );
    FT_UNUSED( filter );

    return FT_THROW( Unimplemented_Feature );
  }


  /* documentation in ftlcdfil.h */

  FT_EXPORT_DEF( FT_Error )
  FT_Library_SetLcdGeometry( FT_Library  library,
                             FT_Vector   sub[3] )
  {
    if ( !library )
      return FT_THROW( Invalid_Library_Handle );

    if ( !sub )
      return FT_THROW( Invalid_Argument );

    ft_memcpy( library->lcd_geometry, sub, 3 * sizeof( FT_Vector ) );

    return FT_Err_Ok;
  }

#endif /* !FT_CONFIG_OPTION_SUBPIXEL_RENDERING */


/* END */