diff options
Diffstat (limited to 'src/raster/ftraster.c')
| -rw-r--r-- | src/raster/ftraster.c | 42 |
1 files changed, 40 insertions, 2 deletions
diff --git a/src/raster/ftraster.c b/src/raster/ftraster.c index 9638dfb..55e2d0d 100644 --- a/src/raster/ftraster.c +++ b/src/raster/ftraster.c @@ -4,7 +4,7 @@ /* */ /* The FreeType glyph rasterizer (body). */ /* */ -/* Copyright 1996-2001, 2002, 2003, 2005, 2007, 2008, 2009, 2010 by */ +/* Copyright 1996-2001, 2002, 2003, 2005, 2007, 2008, 2009, 2010, 2011 by */ /* David Turner, Robert Wilhelm, and Werner Lemberg. */ /* */ /* This file is part of the FreeType project, and may only be used, */ @@ -651,11 +651,33 @@ static void Set_High_Precision( RAS_ARGS Int High ) { + /* + * `precision_step' is used in `Bezier_Up' to decide when to split a + * given y-monotonous Bezier arc that crosses a scanline before + * approximating it as a straight segment. The default value of 32 (for + * low accuracy) corresponds to + * + * 32 / 64 == 0.5 pixels , + * + * while for the high accuracy case we have + * + * 256/ (1 << 12) = 0.0625 pixels . + * + * `precision_jitter' is an epsilon threshold used in + * `Vertical_Sweep_Span' to deal with small imperfections in the Bezier + * decomposition (after all, we are working with approximations only); + * it avoids switching on additional pixels which would cause artifacts + * otherwise. + * + * The value of `precision_jitter' has been determined heuristically. + * + */ + if ( High ) { ras.precision_bits = 12; ras.precision_step = 256; - ras.precision_jitter = 50; + ras.precision_jitter = 30; } else { @@ -2403,6 +2425,14 @@ return; /* no drop-out control */ } + /* undocumented but confirmed: If the drop-out would result in a */ + /* pixel outside of the bounding box, use the pixel inside of the */ + /* bounding box instead */ + if ( pxl < 0 ) + pxl = e1; + else if ( TRUNC( pxl ) >= ras.bWidth ) + pxl = e2; + /* check that the other pixel isn't set */ e1 = pxl == e1 ? e2 : e1; @@ -2579,6 +2609,14 @@ return; /* no drop-out control */ } + /* undocumented but confirmed: If the drop-out would result in a */ + /* pixel outside of the bounding box, use the pixel inside of the */ + /* bounding box instead */ + if ( pxl < 0 ) + pxl = e1; + else if ( TRUNC( pxl ) >= ras.target.rows ) + pxl = e2; + /* check that the other pixel isn't set */ e1 = pxl == e1 ? e2 : e1; |