From: Ben Harris <bjh21@bjh21.me.uk>
Date: Sat, 9 Nov 2024 23:51:36 +0000 (+0000)
Subject: Generate stem hints
X-Git-Tag: bedstead-3.246~41
X-Git-Url: https://www.chiark.greenend.org.uk/ucgi/~bjharris/git?a=commitdiff_plain;h=4254bff53ae9367bf09302ebecded363617af322;p=bedstead.git

Generate stem hints

These are generated from the glyph bitmap by a similar
pattern-matching arrangement that generates the outline.  Then, like
emit_path(), there's an emit_hints() that turns them into valid
charstrings.  The handling of overlapping hints could be cleverer: at
the moment we emit the leftmost-possible set of hints, but we collect
a histogram of where hints are needed so could instead emit the most
useful.  Or even try to do hint substitution.

This makes the Bedstead Web page at 90% zoom much prettier than
before, but it's not as good as the FontForge auto-hinter managed.
Edge hints and counter hints will probably help.
---

diff --git a/bedstead.c b/bedstead.c
index 0de87ff..7522b6e 100644
--- a/bedstead.c
+++ b/bedstead.c
@@ -3746,6 +3746,43 @@ emit_path(void)
 	printf(" endchar");
 }
 
+static void
+emit_hints(int vstems[XSIZE], int hstems[YSIZE])
+{
+	int i, start, size, cur;
+	bool printed;
+
+	cur = 0; printed = false;
+	size = XPIX_S + weight->weight;
+	for (i = 0; i < XSIZE; i++) {
+		if (vstems[i] > 0) {
+			start = i * XPIX_S - weight->weight;
+			printf(" %g %g",
+			       (double)((start - cur) / XSCALE),
+			       (double)(size / XSCALE));
+			cur = start + size;
+			i++; /* Avoid overlapping stems. */
+			printed = true;
+		}
+	}
+	if (printed) printf(" vstem");
+
+	cur = DESCENT * YPIX; printed = false;
+	size = YPIX_S;
+	for (i = YSIZE - 1; i >= 0; i--) {
+		if (hstems[i] > 0) {
+			start = (YSIZE - i - 1) * YPIX_S;
+			printf(" %g %g",
+			       (double)((start - cur) / YSCALE),
+			       (double)(size / YSCALE));
+			cur = start + size;
+			i--; /* Avoid overlapping stems. */
+			printed = true;
+		}
+	}
+	if (printed) printf(" hstem");
+}
+
 /*
  * To vary the weight of Bedstead, we just vary the thickness of
  * vertical strokes.  More precisely, we pretend that the weight
@@ -3883,6 +3920,7 @@ static void
 dochar(struct glyph *g)
 {
 	int x, y;
+	int vstems[XSIZE], hstems[YSIZE];
 
 #define GETPIX(x,y) (getpix(g->data, (x), (y), g->flags))
 #define L GETPIX(x-1, y)
@@ -3894,6 +3932,8 @@ dochar(struct glyph *g)
 #define DL GETPIX(x-1, y+1)
 #define DR GETPIX(x+1, y+1)
 
+	for (x = 0; x < XSIZE; x++) vstems[x] = 0;
+	for (y = 0; y < YSIZE; y++) hstems[y] = 0;
 	clearpath();
 	for (x = 0; x < XSIZE; x++) {
 		for (y = 0; y < YSIZE; y++) {
@@ -3913,6 +3953,14 @@ dochar(struct glyph *g)
 				if (L || DL || D) bl = true;
 				if (R || DR || D) br = true;
 				blackpixel(x, YSIZE - y - 1, bl, br, tr, tl);
+				if (!L && !R && (U || D))
+					vstems[x]++;
+				if (!U && !D && (L || R))
+					hstems[y]++;
+				if (UL + U + UR + L + R + DL + D + DR == 0) {
+					vstems[x]++;
+					hstems[y]++;
+				}
 			} else {
 				bool tl, tr, bl, br;
 
@@ -3930,6 +3978,7 @@ dochar(struct glyph *g)
 	clean_path();
 	adjust_weight();
 	record_lsb(g);
+	emit_hints(vstems, hstems);
 	emit_path();
 }