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config/	-	0755	rm
freetype.h	165119	0644	edit dl rm
ftadvanc.h	5470	0644	edit dl rm
ftbbox.h	2638	0644	edit dl rm
ftbdf.h	5322	0644	edit dl rm
ftbitmap.h	9051	0644	edit dl rm
ftbzip2.h	2786	0644	edit dl rm
ftcache.h	33858	0644	edit dl rm
ftchapters.h	2510	0644	edit dl rm
ftcid.h	4022	0644	edit dl rm
ftcolor.h	8913	0644	edit dl rm
ftdriver.h	47220	0644	edit dl rm
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ftfntfmt.h	2213	0644	edit dl rm
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ftglyph.h	18491	0644	edit dl rm
ftgxval.h	10625	0644	edit dl rm
ftgzip.h	4211	0644	edit dl rm
ftimage.h	39895	0644	edit dl rm
ftincrem.h	10310	0644	edit dl rm
ftlcdfil.h	11739	0644	edit dl rm
ftlist.h	7100	0644	edit dl rm
ftlzw.h	2768	0644	edit dl rm
ftmac.h	7771	0644	edit dl rm
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ftmodapi.h	21777	0644	edit dl rm
ftmoderr.h	6601	0644	edit dl rm
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ftparams.h	5592	0644	edit dl rm
ftpfr.h	4910	0644	edit dl rm
ftrender.h	6625	0644	edit dl rm
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ftsnames.h	7730	0644	edit dl rm
ftstroke.h	21773	0644	edit dl rm
ftsynth.h	3362	0644	edit dl rm
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fttypes.h	14487	0644	edit dl rm
ftwinfnt.h	7966	0644	edit dl rm
t1tables.h	22829	0644	edit dl rm
ttnameid.h	58769	0644	edit dl rm
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tttags.h	5092	0644	edit dl rm

Edit: /usr/include/freetype2/freetype/ftlcdfil.h (11739B)

/****************************************************************************
 *
 * ftlcdfil.h
 *
 *   FreeType API for color filtering of subpixel bitmap glyphs
 *   (specification).
 *
 * Copyright (C) 2006-2020 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.
 *
 */

#ifndef FTLCDFIL_H_
#define FTLCDFIL_H_

#include <freetype/freetype.h>
#include <freetype/ftparams.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:
   *   lcd_rendering
   *
   * @title:
   *   Subpixel Rendering
   *
   * @abstract:
   *   API to control subpixel rendering.
   *
   * @description:
   *   FreeType provides two alternative subpixel rendering technologies. 
   *   Should you define `FT_CONFIG_OPTION_SUBPIXEL_RENDERING` in your
   *   `ftoption.h` file, this enables ClearType-style rendering.
   *   Otherwise, Harmony LCD rendering is enabled.  These technologies are
   *   controlled differently and API described below, although always
   *   available, performs its function when appropriate method is enabled
   *   and does nothing otherwise.
   *
   *   ClearType-style LCD rendering exploits the color-striped structure of
   *   LCD pixels, increasing the available resolution in the direction of
   *   the stripe (usually horizontal RGB) by a factor of~3.  Using the
   *   subpixels coverages unfiltered can create severe color fringes
   *   especially when rendering thin features.  Indeed, to produce
   *   black-on-white text, the nearby color subpixels must be dimmed
   *   equally.
   *
   *   A good 5-tap FIR filter should be applied to subpixel coverages
   *   regardless of pixel boundaries and should have these properties:
   *
   *   1. It should be symmetrical, like {~a, b, c, b, a~}, to avoid
   *      any shifts in appearance.
   *
   *   2. It should be color-balanced, meaning a~+ b~=~c, to reduce color
   *      fringes by distributing the computed coverage for one subpixel to
   *      all subpixels equally.
   *
   *   3. It should be normalized, meaning 2a~+ 2b~+ c~=~1.0 to maintain
   *      overall brightness.
   *
   *   Boxy 3-tap filter {0, 1/3, 1/3, 1/3, 0} is sharper but is less
   *   forgiving of non-ideal gamma curves of a screen (and viewing angles),
   *   beveled filters are fuzzier but more tolerant.
   *
   *   Use the @FT_Library_SetLcdFilter or @FT_Library_SetLcdFilterWeights
   *   API to specify a low-pass filter, which is then applied to
   *   subpixel-rendered bitmaps generated through @FT_Render_Glyph.
   *
   *   Harmony LCD rendering is suitable to panels with any regular subpixel
   *   structure, not just monitors with 3 color striped subpixels, as long
   *   as the color subpixels have fixed positions relative to the pixel
   *   center.  In this case, each color channel is then rendered separately
   *   after shifting the outline opposite to the subpixel shift so that the
   *   coverage maps are aligned.  This method is immune to color fringes
   *   because the shifts do not change integral coverage.
   *
   *   The subpixel geometry must be specified by xy-coordinates for each
   *   subpixel. By convention they may come in the RGB order: {{-1/3, 0},
   *   {0, 0}, {1/3, 0}} for standard RGB striped panel or {{-1/6, 1/4},
   *   {-1/6, -1/4}, {1/3, 0}} for a certain PenTile panel.
   *
   *   Use the @FT_Library_SetLcdGeometry API to specify subpixel positions.
   *   If one follows the RGB order convention, the same order applies to the
   *   resulting @FT_PIXEL_MODE_LCD and @FT_PIXEL_MODE_LCD_V bitmaps.  Note,
   *   however, that the coordinate frame for the latter must be rotated
   *   clockwise.  Harmony with default LCD geometry is equivalent to
   *   ClearType with light filter.
   *
   *   As a result of ClearType filtering or Harmony rendering, the
   *   dimensions of LCD bitmaps can be either wider or taller than the
   *   dimensions of the corresponding outline with regard to the pixel grid.
   *   For example, for @FT_RENDER_MODE_LCD, the filter adds 2~subpixels to
   *   the left, and 2~subpixels to the right.  The bitmap offset values are
   *   adjusted accordingly, so clients shouldn't need to modify their layout
   *   and glyph positioning code when enabling the filter.
   *
   *   The ClearType and Harmony rendering is applicable to glyph bitmaps
   *   rendered through @FT_Render_Glyph, @FT_Load_Glyph, @FT_Load_Char, and
   *   @FT_Glyph_To_Bitmap, when @FT_RENDER_MODE_LCD or @FT_RENDER_MODE_LCD_V
   *   is specified.  This API does not control @FT_Outline_Render and
   *   @FT_Outline_Get_Bitmap.
   *
   *   The described algorithms can completely remove color artefacts when
   *   combined with gamma-corrected alpha blending in linear space.  Each of
   *   the 3~alpha values (subpixels) must by independently used to blend one
   *   color channel.  That is, red alpha blends the red channel of the text
   *   color with the red channel of the background pixel.
   */

/**************************************************************************
   *
   * @enum:
   *   FT_LcdFilter
   *
   * @description:
   *   A list of values to identify various types of LCD filters.
   *
   * @values:
   *   FT_LCD_FILTER_NONE ::
   *     Do not perform filtering.  When used with subpixel rendering, this
   *     results in sometimes severe color fringes.
   *
   *   FT_LCD_FILTER_DEFAULT ::
   *     This is a beveled, normalized, and color-balanced five-tap filter
   *     with weights of [0x08 0x4D 0x56 0x4D 0x08] in 1/256th units.
   *
   *   FT_LCD_FILTER_LIGHT ::
   *     this is a boxy, normalized, and color-balanced three-tap filter with
   *     weights of [0x00 0x55 0x56 0x55 0x00] in 1/256th units.
   *
   *   FT_LCD_FILTER_LEGACY ::
   *   FT_LCD_FILTER_LEGACY1 ::
   *     This filter corresponds to the original libXft color filter.  It
   *     provides high contrast output but can exhibit really bad color
   *     fringes if glyphs are not extremely well hinted to the pixel grid.
   *     This filter is only provided for comparison purposes, and might be
   *     disabled or stay unsupported in the future. The second value is
   *     provided for compatibility with FontConfig, which historically used
   *     different enumeration, sometimes incorrectly forwarded to FreeType.
   *
   * @since:
   *   2.3.0 (`FT_LCD_FILTER_LEGACY1` since 2.6.2)
   */
  typedef enum  FT_LcdFilter_
  {
    FT_LCD_FILTER_NONE    = 0,
    FT_LCD_FILTER_DEFAULT = 1,
    FT_LCD_FILTER_LIGHT   = 2,
    FT_LCD_FILTER_LEGACY1 = 3,
    FT_LCD_FILTER_LEGACY  = 16,

FT_LCD_FILTER_MAX   /* do not remove */

} FT_LcdFilter;

/**************************************************************************
   *
   * @function:
   *   FT_Library_SetLcdFilter
   *
   * @description:
   *   This function is used to change filter applied to LCD decimated
   *   bitmaps, like the ones used when calling @FT_Render_Glyph with
   *   @FT_RENDER_MODE_LCD or @FT_RENDER_MODE_LCD_V.
   *
   * @input:
   *   library ::
   *     A handle to the target library instance.
   *
   *   filter ::
   *     The filter type.
   *
   *     You can use @FT_LCD_FILTER_NONE here to disable this feature, or
   *     @FT_LCD_FILTER_DEFAULT to use a default filter that should work well
   *     on most LCD screens.
   *
   * @return:
   *   FreeType error code.  0~means success.
   *
   * @note:
   *   Since 2.10.3 the LCD filtering is enabled with @FT_LCD_FILTER_DEFAULT.
   *   It is no longer necessary to call this function explicitly except
   *   to choose a different filter or disable filtering altogether with
   *   @FT_LCD_FILTER_NONE.
   *
   *   This function does nothing but returns `FT_Err_Unimplemented_Feature`
   *   if the configuration macro `FT_CONFIG_OPTION_SUBPIXEL_RENDERING` is
   *   not defined in your build of the library.
   *
   * @since:
   *   2.3.0
   */
  FT_EXPORT( FT_Error )
  FT_Library_SetLcdFilter( FT_Library    library,
                           FT_LcdFilter  filter );

/**************************************************************************
   *
   * @function:
   *   FT_Library_SetLcdFilterWeights
   *
   * @description:
   *   This function can be used to enable LCD filter with custom weights,
   *   instead of using presets in @FT_Library_SetLcdFilter.
   *
   * @input:
   *   library ::
   *     A handle to the target library instance.
   *
   *   weights ::
   *     A pointer to an array; the function copies the first five bytes and
   *     uses them to specify the filter weights in 1/256th units.
   *
   * @return:
   *   FreeType error code.  0~means success.
   *
   * @note:
   *   This function does nothing but returns `FT_Err_Unimplemented_Feature`
   *   if the configuration macro `FT_CONFIG_OPTION_SUBPIXEL_RENDERING` is
   *   not defined in your build of the library.
   *
   *   LCD filter weights can also be set per face using @FT_Face_Properties
   *   with @FT_PARAM_TAG_LCD_FILTER_WEIGHTS.
   *
   * @since:
   *   2.4.0
   */
  FT_EXPORT( FT_Error )
  FT_Library_SetLcdFilterWeights( FT_Library      library,
                                  unsigned char  *weights );

/**************************************************************************
   *
   * @type:
   *   FT_LcdFiveTapFilter
   *
   * @description:
   *   A typedef for passing the five LCD filter weights to
   *   @FT_Face_Properties within an @FT_Parameter structure.
   *
   * @since:
   *   2.8
   *
   */
#define FT_LCD_FILTER_FIVE_TAPS  5

typedef FT_Byte  FT_LcdFiveTapFilter[FT_LCD_FILTER_FIVE_TAPS];

/**************************************************************************
   *
   * @function:
   *   FT_Library_SetLcdGeometry
   *
   * @description:
   *   This function can be used to modify default positions of color
   *   subpixels, which controls Harmony LCD rendering.
   *
   * @input:
   *   library ::
   *     A handle to the target library instance.
   *
   *   sub ::
   *     A pointer to an array of 3 vectors in 26.6 fractional pixel format;
   *     the function modifies the default values, see the note below.
   *
   * @return:
   *   FreeType error code.  0~means success.
   *
   * @note:
   *   Subpixel geometry examples:
   *
   *   - {{-21, 0}, {0, 0}, {21, 0}} is the default, corresponding to 3 color
   *   stripes shifted by a third of a pixel. This could be an RGB panel.
   *
   *   - {{21, 0}, {0, 0}, {-21, 0}} looks the same as the default but can
   *   specify a BGR panel instead, while keeping the bitmap in the same
   *   RGB888 format.
   *
   *   - {{0, 21}, {0, 0}, {0, -21}} is the vertical RGB, but the bitmap
   *   stays RGB888 as a result.
   *
   *   - {{-11, 16}, {-11, -16}, {22, 0}} is a certain PenTile arrangement.
   *
   *   This function does nothing and returns `FT_Err_Unimplemented_Feature`
   *   in the context of ClearType-style subpixel rendering when
   *   `FT_CONFIG_OPTION_SUBPIXEL_RENDERING` is defined in your build of the
   *   library.
   *
   * @since:
   *   2.10.0
   */
  FT_EXPORT( FT_Error )
  FT_Library_SetLcdGeometry( FT_Library  library,
                             FT_Vector   sub[3] );

/* */

FT_END_HEADER

#endif /* FTLCDFIL_H_ */

/* END */

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