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[autofit] add tilde unflattening algorithm 

* src/autofit/aflatin.c add tilde unflattening algorithm, applied
based on adjustment database and reverse character map
* src/autofit/aflatin.c fix adjustment database entry for n with tilde
This commit is contained in:
Craig White 2023-11-03 01:07:02 -04:00
parent 41bb41de9a
commit ba0b1a57e3
2 changed files with 223 additions and 1 deletions
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2
src/autofit/afadjust.c
View File

@ -52,7 +52,7 @@ adjustment_database[] =
{0xEC, AF_VERTICAL_ADJUSTMENT_TOP_CONTOUR_UP, 0},
{0xED, AF_VERTICAL_ADJUSTMENT_TOP_CONTOUR_UP, 0},
{0xEE, AF_VERTICAL_ADJUSTMENT_TOP_CONTOUR_UP, 0},
{0xF1, AF_VERTICAL_ADJUSTMENT_TOP_CONTOUR_UP, 0}, /*n with tilde*/
{0xF1, AF_VERTICAL_ADJUSTMENT_TOP_CONTOUR_UP, 1}, /*n with tilde*/
{0xF2, AF_VERTICAL_ADJUSTMENT_TOP_CONTOUR_UP, 0},
{0xF3, AF_VERTICAL_ADJUSTMENT_TOP_CONTOUR_UP, 0},
{0xF4, AF_VERTICAL_ADJUSTMENT_TOP_CONTOUR_UP, 0},

222
src/autofit/aflatin.c
View File

@ -2798,6 +2798,221 @@ af_find_highest_contour( AF_GlyphHints hints ) {
return highest_contour;
}
static void
af_remove_segments_containing_point(AF_GlyphHints hints, AF_Point point)
{
AF_AxisHints axis = &hints->axis[AF_DIMENSION_VERT];
AF_Segment segments = axis->segments;
for ( FT_Int i = 0; i < axis->num_segments; i++ )
{
AF_Segment seg = &segments[i];
FT_Bool remove = 0;
AF_Point p = seg->first;
while ( 1 )
{
if ( p == point )
{
remove = 1;
break;
}
if (p == seg->last) {
break;
}
p = p->next;
}
if ( remove )
{
/* first, check the first and last fields of the edge */
AF_Edge edge = seg->edge;
if ( edge->first == seg && edge->last == seg )
{
/* The edge only consists of the segment to be removed. remove the edge*/
*edge = axis->edges[--axis->num_edges];
}
else
{
if ( edge->first == seg )
{
edge->first = seg->edge_next;
}
if ( edge->last == seg )
{
edge->last = edge->first;
while ( edge->last->edge_next != seg )
{
edge->last = edge->last->edge_next;
}
}
}
/* Now, delete the segment */
*seg = axis->segments[--axis->num_segments];
i--; /* we have to check the new segment at this position */
}
}
}
/*remove all segments containing points on the tilde contour*/
static void
af_latin_remove_tilde_points_from_edges( AF_GlyphHints hints,
FT_Int glyph_index )
{
FT_Int highest_contour = af_find_highest_contour(hints);
AF_Point first_point = hints->contours[highest_contour];
/* search for any curve tips that are on a y extrema, and delete any
segments that contain this point.*/
AF_Point p = first_point;
do
{
p = p->next;
if ( /*!(p->flags & AF_FLAG_CONTROL)
&& p->prev->y == p->y && p->next->y == p->y
&& p->prev->flags & AF_FLAG_CONTROL
&& p->next->flags & AF_FLAG_CONTROL*/ 1 )
{
FT_TRACE4(("%p", p));
af_remove_segments_containing_point( hints, p );
}
} while ( p != first_point );
}
/*
The tilde unflattening algorithm sometimes goes too far and makes an
unusually high tilde, where decreasing the ppem will increase the height
instead of a steady decrease in height as less pixels are used.
The n tilde on times new roman with forced autofitting on,
16.5-18 ppem font size exhibits this behaviour.
*/
void
af_latin_stretch_tildes( AF_GlyphHints hints,
FT_Int glyph_index )
{
FT_Int highest_contour = af_find_highest_contour( hints );
AF_Point p = hints->contours[highest_contour];
AF_Point first_point = p;
FT_Pos min_y, max_y;
min_y = max_y = p->y;
FT_Short min_fy, max_fy;
min_fy = max_fy = p->fy;
do
{
p = p->next;
if ( p->y < min_y )
{
min_y = p->y;
}
if ( p->y > max_y )
{
max_y = p->y;
}
if ( p->fy < min_fy )
{
min_fy = p->fy;
}
if ( p->fy > max_fy )
{
max_fy = p->fy;
}
}
while ( p != first_point );
FT_Pos min_measurement = 32000;
FT_UInt measurements_taken = 0;
do
{
p = p->next;
if ( !(p->flags & AF_FLAG_CONTROL)
&& p->prev->y == p->y && p->next->y == p->y
&& p->y != min_y && p->y != max_y
&& p->prev->flags & AF_FLAG_CONTROL
&& p->next->flags & AF_FLAG_CONTROL )
{
/* This point could be a candidate. Find the next and previous on-curve */
/* points, and make sure they are both either above or below the point, */
/* Then make the measurement */
AF_Point prevOn = p->prev;
AF_Point nextOn = p->next;
while ( prevOn->flags & AF_FLAG_CONTROL )
{
prevOn = prevOn->prev;
}
while ( nextOn->flags & AF_FLAG_CONTROL )
{
nextOn = nextOn->next;
}
FT_Pos measurement;
if ( nextOn->y > p->y && prevOn->y > p->y )
{
measurement = p->y - min_y;
}
else if ( nextOn->y < p->y && prevOn->y < p->y )
{
measurement = max_y - p->y;
}
else
{
continue;
}
if (measurement < min_measurement)
{
min_measurement = measurement;
}
measurements_taken++;
}
}
while ( p != first_point );
FT_Pos height = max_y - min_y;
FT_Pos target_height = min_measurement + 64;
if ( height >= target_height )
{
return;
}
p = first_point;
do
{
p = p->next;
p->y = ((p->y - min_y) * target_height / height) + min_y;
p->fy = ((p->fy - min_fy) * target_height / height) + min_fy;
p->oy = p->y;
if ( !(p->flags & AF_FLAG_CONTROL) )
p->flags |= AF_FLAG_TOUCH_Y;
}
while ( p != first_point );
FT_Pos new_min_y, new_max_y;
new_min_y = new_max_y = first_point->y;
p = first_point;
do {
p = p->next;
if ( p->y < new_min_y )
{
new_min_y = p->y;
}
if ( p->y > new_max_y )
{
new_max_y = p->y;
}
}
while ( p != first_point );
}
/*True if the given contour overlaps horizontally with the bounding box
Of all other contours combined.
This is a helper for af_glyph_hints_apply_vertical_separation_adjustments */
@ -3886,11 +4101,18 @@ af_glyph_hints_apply_vertical_separation_adjustments( AF_GlyphHints hints,
if ( AF_HINTS_DO_VERTICAL( hints ) )
{
FT_Bool is_tilde = af_lookup_tilde_correction_type( metrics->root.reverse_charmap, glyph_index );
if ( is_tilde ) {
af_latin_stretch_tildes( hints, glyph_index );
}
axis = &metrics->axis[AF_DIMENSION_VERT];
error = af_latin_hints_detect_features( hints,
axis->width_count,
axis->widths,
AF_DIMENSION_VERT );
if ( is_tilde ) {
af_latin_remove_tilde_points_from_edges( hints, glyph_index );
}
if ( error )
goto Exit;