Generate Birbaslo SDF font

Makefile

@@ -21,7 +21,7 @@ test:
 	npm test
 
 count:
-	ag -g 'cc$$|hh$$|tsx?$$|frag$$|vert$$' --ignore='tests' | xargs wc -l
+	ag -g 'c$$|cc$$|hh$$|tsx?$$|frag$$|vert$$' --ignore='tests' | xargs wc -l
 
 # deploy to github pages
 deploy:

precompute/Makefile

@@ -1,2 +1,6 @@
+../public/assets/font-sheet.png: precompute-font
+	./precompute-font
+	convert /tmp/font-sheet.ppm ../public/assets/font-sheet.png
+
 precompute-font: precompute-font.c ../vendor/stb_truetype.h
 	gcc -o precompute-font precompute-font.c -lm

precompute/precompute-font.c

@@ -2,37 +2,111 @@
 #define STB_TRUETYPE_IMPLEMENTATION
 #include "../vendor/stb_truetype.h"
 
-int main(void) {
-  stbtt_fontinfo font;
-  unsigned char ttf_buffer[1<<20];
+#define DEBUG 0
 
-  fread(ttf_buffer, 1, 1<<25, fopen("/home/jcreed/.fonts/Birbaslo.ttf", "rb"));
-
-  stbtt_InitFont(&font, ttf_buffer, stbtt_GetFontOffsetForIndex(ttf_buffer,0));
+#define SPRITE_W 64
+#define SPRITE_H 64
+#define CELLS_W 8
+#define CELLS_H 8
+#define FINAL_W (SPRITE_W * CELLS_W)
+#define FINAL_H (SPRITE_H * CELLS_H)
+#define PADDING 5
+#define ONEDGE 128
 
+void  splat_letter(const stbtt_fontinfo *font, float scale, int codepoint, int sprite_x, int sprite_y, int ascent, char *final) {
   int height;
   int width;
   int xoff;
   int yoff;
-  int glyph = stbtt_FindGlyphIndex(&font, 0x2603);
-  unsigned char *bitmap = stbtt_GetGlyphSDF(&font,
-                                            stbtt_ScaleForPixelHeight(&font, 96), /*scale*/
-                                                glyph, /* glyph index */
-                                                5, /* int padding */
-                                                180, /* unsigned char onedge_value */
-                                                36.0, /* float pixel_dist_scale */
-                                                &width, /* int *width */
-                                                &height, /* int *height */
-                                                &xoff, /* int *xoff */
-                                                &yoff  /* int *yoff */
-                                                );
-  printf("P2 %d %d 255\n", width, height);
-  for (int i = 0; i < height; i++) {
-    for (int j = 0; j < width; j++) {
-      printf("%d ", bitmap[i * width + j]);
+  int glyph = stbtt_FindGlyphIndex(font, codepoint);
+
+  int advance;
+  int lsb;
+  stbtt_GetCodepointHMetrics(font, codepoint, &advance, &lsb);
+
+  unsigned char *bitmap = stbtt_GetGlyphSDF(font,
+                                            scale, /*scale*/
+                                            glyph, /* glyph index */
+                                            PADDING, /* int padding */
+                                            ONEDGE, /* unsigned char onedge_value */
+                                            ONEDGE / (float)PADDING, /* float pixel_dist_scale */
+                                            &width, /* int *width */
+                                            &height, /* int *height */
+                                            &xoff, /* int *xoff */
+                                            &yoff  /* int *yoff */
+                                            );
+
+  int real_width = width - 2 * PADDING;
+  int char_left = -xoff;
+  int char_right = -xoff + scale * advance;
+  if (DEBUG)
+    fprintf(stderr, "advance %f lsb %f gap %d\n", scale * advance, scale * lsb, char_right - char_left);
+  int char_baseline = -yoff;
+
+  for (int sy = 0; sy < SPRITE_H; sy++) {
+    for (int sx = 0; sx < SPRITE_W; sx++) {
+      int lx = sx - xoff - (SPRITE_W  - advance * scale) / 2;
+      int ly = sy - (SPRITE_H - ascent * scale) / 2;
+      int x = sprite_x * SPRITE_W + sx;
+      int y = sprite_y * SPRITE_H + sy;
+      int ix = 3 * (y * FINAL_W + x);
+      int lix = ly * width + lx;
+      // The red channel is the authoritative SDF.
+      // But we stick some other info in green and blue just for debugging.
+      if (lx >= 0 && ly >= 0 && lx < width && ly < height) {
+        final[ix + 0] = bitmap[lix];
+        final[ix + 1] = bitmap[lix];
+        final[ix + 2] = bitmap[lix];
+      }
+      else {
+        final[ix + 0] = 0;
+        final[ix + 1] = 0;
+        final[ix + 2] = 255;
+      }
+      if ((lx >= char_left && lx <= char_right) && ly == char_baseline) {
+        final[ix + 1] = 255;
+        final[ix + 2] = 0;
+      }
     }
-    printf("\n");
   }
+
   stbtt_FreeSDF(bitmap, (void *)0 /*void *userdata*/);
+}
+
+int main(void) {
+  stbtt_fontinfo font;
+  unsigned char ttf_buffer[1<<20];
+  unsigned char final[3 * FINAL_W * FINAL_H];
+  FILE *fontfile = fopen("../public/assets/Birbaslo.ttf", "rb");
+  if (!fontfile) {
+    printf("Can't find font\n");
+    exit(1);
+  }
+  fread(ttf_buffer, 1, 1<<25, fontfile);
+
+  stbtt_InitFont(&font, ttf_buffer, stbtt_GetFontOffsetForIndex(ttf_buffer,0));
+
+  int ascent;
+  float scale = stbtt_ScaleForPixelHeight(&font, 55);
+  stbtt_GetFontVMetrics(&font, &ascent,0,0);
+  if (DEBUG) {
+    fprintf(stderr, "ascent %f\n", ascent * scale);
+  }
+
+  for (int i = 0; i <= 25; i++) {
+    splat_letter(&font, scale, 65 + i, i / CELLS_W, i % CELLS_W, ascent, final);
+  }
+
+  FILE *fsfp = fopen("/tmp/font-sheet.ppm", "w");
+  fprintf(fsfp, "P3 %d %d 255\n", FINAL_W, FINAL_H);
+
+  for (int i = 0; i < FINAL_W; i++) {
+    for (int j = 0; j < FINAL_H; j++) {
+      int ix = 3 * (i * FINAL_W + j);
+      fprintf(fsfp, "%d %d %d\n", final[ix], final[ix+1], final[ix+2]);
+    }
+    fprintf(fsfp, "\n");
+  }
+  fclose(fsfp);
 
 }