Commit 1178227b39a4eeecbefad226d4a753b345a16eb1
2019-05-11T09:29:19
[truetype] Increase precision of font variation (#54371). This patch make FreeType use font units in 26.6 format internally instead of integers. * src/truetype/ttgxvar.c (FT_fixedToFdot6): New macro. (TT_Vary_Apply_Glyph_Deltas): Add argument to output unrounded font coordinates. * src/truetype/ttgxvar.h: Updated. * src/truetype/ttgload.c (TT_Process_Simple_Glyph): Use `extra_points2' array to temporarily hold unrounded point coordinates; use them to compute scaled coordinates and linear advance width and height. (load_truetype_code): Adjust similarly.
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diff --git a/ChangeLog b/ChangeLog
index 31a84ee..52492cd 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,23 @@
2019-05-09 Werner Lemberg <wl@gnu.org>
+ [truetype] Increase precision of font variation (#54371).
+
+ This patch make FreeType use font units in 26.6 format internally
+ instead of integers.
+
+ * src/truetype/ttgxvar.c (FT_fixedToFdot6): New macro.
+ (TT_Vary_Apply_Glyph_Deltas): Add argument to output unrounded font
+ coordinates.
+ * src/truetype/ttgxvar.h: Updated.
+
+ * src/truetype/ttgload.c (TT_Process_Simple_Glyph): Use
+ `extra_points2' array to temporarily hold unrounded point
+ coordinates; use them to compute scaled coordinates and linear
+ advance width and height.
+ (load_truetype_code): Adjust similarly.
+
+2019-05-09 Werner Lemberg <wl@gnu.org>
+
* src/truetype/ttgload.c (TT_Process_Simple_Glyph): Minor.
2019-05-08 Alexei Podtelezhnikov <apodtele@gmail.com>
diff --git a/include/freetype/freetype.h b/include/freetype/freetype.h
index f758ea1..2f7863c 100644
--- a/include/freetype/freetype.h
+++ b/include/freetype/freetype.h
@@ -1766,6 +1766,13 @@ FT_BEGIN_HEADER
* transformed, distorted, emboldened, etc. However, it must not be
* freed.
*
+ * [Since 2.10.1] If @FT_LOAD_NO_SCALE is set, outline coordinates of
+ * OpenType variation fonts for a selected instance are internally
+ * handled as 26.6 fractional font units but returned as (rounded)
+ * integers, as expected. To get unrounded font units, don't use
+ * @FT_LOAD_NO_SCALE but load the glyph with @FT_LOAD_NO_HINTING and
+ * scale it, using the font's `units_per_EM` value as the ppem.
+ *
* num_subglyphs ::
* The number of subglyphs in a composite glyph. This field is only
* valid for the composite glyph format that should normally only be
diff --git a/src/truetype/ttgload.c b/src/truetype/ttgload.c
index d88f4c4..d4a87ef 100644
--- a/src/truetype/ttgload.c
+++ b/src/truetype/ttgload.c
@@ -925,6 +925,7 @@
FT_GlyphLoader gloader = loader->gloader;
FT_Error error = FT_Err_Ok;
FT_Outline* outline;
+ FT_Vector* unrounded;
FT_Int n_points;
@@ -950,20 +951,26 @@
if ( FT_IS_NAMED_INSTANCE( FT_FACE( loader->face ) ) ||
FT_IS_VARIATION( FT_FACE( loader->face ) ) )
{
- /* Deltas apply to the unscaled data. */
+ /* Deltas apply to the unscaled data. */
+ /* We temporarily use `extra_points2' to hold unrounded values. */
+ unrounded = gloader->current.extra_points2;
error = TT_Vary_Apply_Glyph_Deltas( loader->face,
loader->glyph_index,
outline,
+ unrounded,
(FT_UInt)n_points );
/* recalculate linear horizontal and vertical advances */
/* if we don't have HVAR and VVAR, respectively */
+
+ /* XXX: change all FreeType modules to store `linear' and `vadvance' */
+ /* in 26.6 format before the `base' module scales them to 16.16 */
if ( !( loader->face->variation_support & TT_FACE_FLAG_VAR_HADVANCE ) )
- loader->linear = outline->points[n_points - 3].x -
- outline->points[n_points - 4].x;
+ loader->linear = FT_PIX_ROUND( unrounded[n_points - 3].x -
+ unrounded[n_points - 4].x ) / 64;
if ( !( loader->face->variation_support & TT_FACE_FLAG_VAR_VADVANCE ) )
- loader->vadvance = outline->points[n_points - 1].x -
- outline->points[n_points - 2].x;
+ loader->vadvance = FT_PIX_ROUND( unrounded[n_points - 1].x -
+ unrounded[n_points - 2].x ) / 64;
if ( error )
return error;
@@ -1013,10 +1020,17 @@
/* compensate for any scaling by de/emboldening; */
/* the amount was determined via experimentation */
if ( x_scale_factor != 1000 && ppem > 11 )
+ {
+ FT_Vector* orig_points = outline->points;
+
+
+ outline->points = unrounded;
FT_Outline_EmboldenXY( outline,
FT_MulFix( 1280 * ppem,
1000 - x_scale_factor ),
0 );
+ outline->points = orig_points;
+ }
do_scale = TRUE;
}
}
@@ -1037,10 +1051,10 @@
if ( do_scale )
{
- for ( ; vec < limit; vec++ )
+ for ( ; vec < limit; vec++, unrounded++ )
{
- vec->x = FT_MulFix( vec->x, x_scale );
- vec->y = FT_MulFix( vec->y, y_scale );
+ vec->x = FT_MulDiv( unrounded->x, x_scale, 0x10000L * 64 );
+ vec->y = FT_MulDiv( unrounded->y, y_scale, 0x10000L * 64 );
}
}
@@ -1678,6 +1692,9 @@
short contours[4] = { 0, 1, 2, 3 };
FT_Outline outline;
+ /* unrounded values */
+ FT_Vector unrounded[4];
+
points[0].x = loader->pp1.x;
points[0].y = loader->pp1.y;
@@ -1699,6 +1716,7 @@
error = TT_Vary_Apply_Glyph_Deltas( loader->face,
glyph_index,
&outline,
+ unrounded,
(FT_UInt)outline.n_points );
if ( error )
goto Exit;
@@ -1716,9 +1734,11 @@
/* recalculate linear horizontal and vertical advances */
/* if we don't have HVAR and VVAR, respectively */
if ( !( loader->face->variation_support & TT_FACE_FLAG_VAR_HADVANCE ) )
- loader->linear = loader->pp2.x - loader->pp1.x;
+ loader->linear = FT_PIX_ROUND( unrounded[1].x -
+ unrounded[0].x ) / 64;
if ( !( loader->face->variation_support & TT_FACE_FLAG_VAR_VADVANCE ) )
- loader->vadvance = loader->pp4.x - loader->pp3.x;
+ loader->vadvance = FT_PIX_ROUND( unrounded[3].x -
+ unrounded[2].x ) / 64;
}
#endif /* TT_CONFIG_OPTION_GX_VAR_SUPPORT */
@@ -1858,9 +1878,10 @@
FT_SubGlyph subglyph;
FT_Outline outline;
- FT_Vector* points = NULL;
- char* tags = NULL;
- short* contours = NULL;
+ FT_Vector* points = NULL;
+ char* tags = NULL;
+ short* contours = NULL;
+ FT_Vector* unrounded = NULL;
limit = (short)gloader->current.num_subglyphs;
@@ -1874,9 +1895,10 @@
outline.tags = NULL;
outline.contours = NULL;
- if ( FT_NEW_ARRAY( points, outline.n_points ) ||
- FT_NEW_ARRAY( tags, outline.n_points ) ||
- FT_NEW_ARRAY( contours, outline.n_points ) )
+ if ( FT_NEW_ARRAY( points, outline.n_points ) ||
+ FT_NEW_ARRAY( tags, outline.n_points ) ||
+ FT_NEW_ARRAY( contours, outline.n_points ) ||
+ FT_NEW_ARRAY( unrounded, outline.n_points ) )
goto Exit1;
subglyph = gloader->current.subglyphs;
@@ -1925,6 +1947,7 @@
face,
glyph_index,
&outline,
+ unrounded,
(FT_UInt)outline.n_points ) ) )
goto Exit1;
@@ -1952,14 +1975,17 @@
/* recalculate linear horizontal and vertical advances */
/* if we don't have HVAR and VVAR, respectively */
if ( !( face->variation_support & TT_FACE_FLAG_VAR_HADVANCE ) )
- loader->linear = loader->pp2.x - loader->pp1.x;
+ loader->linear = FT_PIX_ROUND( unrounded[1].x -
+ unrounded[0].x ) / 64;
if ( !( face->variation_support & TT_FACE_FLAG_VAR_VADVANCE ) )
- loader->vadvance = loader->pp4.x - loader->pp3.x;
+ loader->vadvance = FT_PIX_ROUND( unrounded[3].x -
+ unrounded[2].x ) / 64;
Exit1:
FT_FREE( outline.points );
FT_FREE( outline.tags );
FT_FREE( outline.contours );
+ FT_FREE( unrounded );
if ( error )
goto Exit;
diff --git a/src/truetype/ttgxvar.c b/src/truetype/ttgxvar.c
index 56b5b6d..317340a 100644
--- a/src/truetype/ttgxvar.c
+++ b/src/truetype/ttgxvar.c
@@ -68,12 +68,14 @@
/* some macros we need */
-#define FT_fdot14ToFixed( x ) \
- ( (FT_Fixed)( (FT_ULong)(x) << 2 ) )
-#define FT_intToFixed( i ) \
- ( (FT_Fixed)( (FT_ULong)(i) << 16 ) )
-#define FT_fixedToInt( x ) \
- ( (FT_Short)( ( (FT_UInt32)(x) + 0x8000U ) >> 16 ) )
+#define FT_fdot14ToFixed( x ) \
+ ( (FT_Fixed)( (FT_ULong)(x) << 2 ) )
+#define FT_intToFixed( i ) \
+ ( (FT_Fixed)( (FT_ULong)(i) << 16 ) )
+#define FT_fixedToInt( x ) \
+ ( (FT_Short)( ( (FT_UInt32)(x) + 0x8000U ) >> 16 ) )
+#define FT_fixedToFdot6( x ) \
+ ( (FT_Pos)( ( (FT_UInt32)(x) + 0x20 ) >> 10 ) )
/**************************************************************************
@@ -3674,6 +3676,11 @@
* outline ::
* The outline to change.
*
+ * @Output:
+ * unrounded ::
+ * An array with `n_points' elements that is filled with unrounded
+ * point coordinates (in 26.6 format).
+ *
* @Return:
* FreeType error code. 0 means success.
*/
@@ -3681,6 +3688,7 @@
TT_Vary_Apply_Glyph_Deltas( TT_Face face,
FT_UInt glyph_index,
FT_Outline* outline,
+ FT_Vector* unrounded,
FT_UInt n_points )
{
FT_Error error;
@@ -4068,6 +4076,11 @@
for ( i = 0; i < n_points; i++ )
{
+ unrounded[i].x = INT_TO_F26DOT6( outline->points[i].x ) +
+ FT_fixedToFdot6( point_deltas_x[i] );
+ unrounded[i].y = INT_TO_F26DOT6( outline->points[i].y ) +
+ FT_fixedToFdot6( point_deltas_y[i] );
+
outline->points[i].x += FT_fixedToInt( point_deltas_x[i] );
outline->points[i].y += FT_fixedToInt( point_deltas_y[i] );
}
diff --git a/src/truetype/ttgxvar.h b/src/truetype/ttgxvar.h
index 7e8d976..07c99b6 100644
--- a/src/truetype/ttgxvar.h
+++ b/src/truetype/ttgxvar.h
@@ -416,6 +416,7 @@ FT_BEGIN_HEADER
TT_Vary_Apply_Glyph_Deltas( TT_Face face,
FT_UInt glyph_index,
FT_Outline* outline,
+ FT_Vector* unrounded,
FT_UInt n_points );
FT_LOCAL( FT_Error )