[freetype2] master e592982: [sdf] Improve documentation.

[Werner Lemberg]

branch: master
commit e592982a836c41050600d63ecf449ff8ab6a9a76
Author: Anuj Verma <anujv@iitbhilai.ac.in>
Commit: Werner Lemberg <wl@gnu.org>

    [sdf] Improve documentation.
---
 include/freetype/freetype.h | 14 +++++++-------
 src/sdf/ftsdf.c             |  3 ++-
 2 files changed, 9 insertions(+), 8 deletions(-)

diff --git a/include/freetype/freetype.h b/include/freetype/freetype.h
index 29a0f71..f393e3d 100644
--- a/include/freetype/freetype.h
+++ b/include/freetype/freetype.h
@@ -3307,13 +3307,13 @@ FT_BEGIN_HEADER
    *     pixels and use the @FT_PIXEL_MODE_LCD_V mode.
    *
    *   FT_RENDER_MODE_SDF ::
-   *     This mode corresponds to 8-bit signed distance fields (SDF)
-   *     bitmaps.  Each 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.
-   *     Check the note below on how to convert the output values to usable
-   *     data.
+   *     This mode corresponds to 8-bit, single-channel signed distance field
+   *     (SDF) bitmaps.  Each pixel in the SDF grid is the value from the
+   *     pixel's position to the nearest glyph's 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.  Check the note below on how to convert the output values
+   *     to usable data.
    *
    * @note:
    *   The selected render mode only affects vector glyphs of a font.
diff --git a/src/sdf/ftsdf.c b/src/sdf/ftsdf.c
index 65a8f32..d3722b1 100644
--- a/src/sdf/ftsdf.c
+++ b/src/sdf/ftsdf.c
@@ -41,7 +41,8 @@
    *     file `ftbsdf.c` for more.
    *
    *   * The basic idea of generating the SDF is taken from Viktor Chlumsky's
-   *     research paper.
+   *     research paper.  The paper explains both single and multi-channel
+   *     SDF, however, this implementation only generates single-channel SDF.
    *
    *       Chlumsky, Viktor: Shape Decomposition for Multi-channel Distance
    *       Fields.  Master's thesis.  Czech Technical University in Prague,