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[freetype2] gsoc-craig-2023-final ba0b1a57e: [autofit] add tilde unflatt
From: |
Werner Lemberg |
Subject: |
[freetype2] gsoc-craig-2023-final ba0b1a57e: [autofit] add tilde unflattening algorithm |
Date: |
Fri, 3 Nov 2023 01:36:01 -0400 (EDT) |
branch: gsoc-craig-2023-final
commit ba0b1a57e3d29c2bf88cc64fe9dba226710f11bc
Author: Craig White <gerzytet@gmail.com>
Commit: Craig White <gerzytet@gmail.com>
[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
---
src/autofit/afadjust.c | 2 +-
src/autofit/aflatin.c | 222 +++++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 223 insertions(+), 1 deletion(-)
diff --git a/src/autofit/afadjust.c b/src/autofit/afadjust.c
index a340716e6..536956eba 100644
--- a/src/autofit/afadjust.c
+++ b/src/autofit/afadjust.c
@@ -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},
diff --git a/src/autofit/aflatin.c b/src/autofit/aflatin.c
index 20d49f5fe..2331eaef1 100644
--- a/src/autofit/aflatin.c
+++ b/src/autofit/aflatin.c
@@ -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;
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