[freetype2] GSoC-2020-anuj 8cce50b: Be more explicit about the output of the SDF rasterizers.

[Anuj Verma]

branch: GSoC-2020-anuj
commit 8cce50b9b8d770f03d32abf260a8602c220c5e02
Author: Anuj Verma <anujv@iitbhilai.ac.in>
Commit: Anuj Verma <anujv@iitbhilai.ac.in>

    Be more explicit about the output of the SDF rasterizers.
    
    * include/freetype/fttypes.h (FT_F6Dot10): Add a new data type which can be\
      used to convert the output buffer appropriately.
    
    * include/freetype/freetype.h (FT_Render_Mode): Add information about the
      output while using `FT_RENDER_MODE_SDF'.
    
    * include/freetype/ftimage.h (FT_Pixel_Mode): Add more information about the
      `FT_PIXEL_MODE_GRAY16' pixel mode.
---
 include/freetype/freetype.h |  4 +++-
 include/freetype/ftimage.h  |  6 ++++--
 include/freetype/fttypes.h  | 12 ++++++++++++
 3 files changed, 19 insertions(+), 3 deletions(-)

diff --git a/include/freetype/freetype.h b/include/freetype/freetype.h
index aca7fcf..4b7da64 100644
--- a/include/freetype/freetype.h
+++ b/include/freetype/freetype.h
@@ -3247,7 +3247,9 @@ FT_BEGIN_HEADER
    *     pixel in a SDF bitmap contains information about the nearest edge of
    *     the glyph outline.  The distances are calculated from the center of
    *     the pixel and are positive if they are filled by the outline (i.e.
-   *     inside the outline) and negative otherwise.
+   *     inside the outline) and negative otherwise.  The output bitmap buffer
+   *     is represented as 6.10 fixed point values, use @FT_6Dot10 and convert
+   *     accordingly.
    *
    * @note:
    *   The selected render mode only affects vector glyphs of a font.
diff --git a/include/freetype/ftimage.h b/include/freetype/ftimage.h
index 5b41ca2..b2b9f78 100644
--- a/include/freetype/ftimage.h
+++ b/include/freetype/ftimage.h
@@ -160,8 +160,10 @@ FT_BEGIN_HEADER
    *   FT_PIXEL_MODE_GRAY16 ::
    *     A 16-bit per pixel bitmap used to represent signed distances in a
    *     signed distance field bitmap.  This is currently only used while
-   *     rendering using @FT_RENDER_MODE_SDF.  Note that this is a 2.14
-   *     fixed-point fractional value.
+   *     rendering using @FT_RENDER_MODE_SDF.  One Impotant Note:
+   *     This pixel format is represented as 6.10 fixed point format.  That
+   *     means you have to divide the values by 1024.0F in order to get
+   *     actual data that is outputted by the SDF rasterizers.
    *
    *   FT_PIXEL_MODE_LCD ::
    *     An 8-bit bitmap, representing RGB or BGR decimated glyph images used
diff --git a/include/freetype/fttypes.h b/include/freetype/fttypes.h
index aaeb9e8..8200ba0 100644
--- a/include/freetype/fttypes.h
+++ b/include/freetype/fttypes.h
@@ -78,6 +78,7 @@ FT_BEGIN_HEADER
    *   FT_FWord
    *   FT_UFWord
    *   FT_F2Dot14
+   *   FT_F6Dot10
    *   FT_UnitVector
    *   FT_F26Dot6
    *   FT_Data
@@ -267,6 +268,17 @@ FT_BEGIN_HEADER
   /**************************************************************************
    *
    * @type:
+   *   FT_F6Dot10
+   *
+   * @description:
+   *   A signed 6.10 fixed-point type used for signed distance values.
+   */
+  typedef signed short  FT_F6Dot10;
+
+
+  /**************************************************************************
+   *
+   * @type:
    *   FT_F26Dot6
    *
    * @description: