Add functions to draw text

lib/plot.py

@@ -2,6 +2,7 @@
 
 import cairo
 import numpy as np
+from HersheyFonts import HersheyFonts
 
 
 class Paper:
@@ -135,6 +136,17 @@ A6_PORTRAIT = Paper(105, 148, 8)
 A6_LANDSCAPE = Paper(148, 105, 8)
 
 
+def _measure_text(hf, text):
+    points = np.array([point for stroke in hf.strokes_for_text(text)
+                      for point in stroke])
+    return {
+        'x': points[:, 0].min(),
+        'y': points[:, 1].min(),
+        'width': points[:, 0].max() - points[:, 0].min(),
+        'height': points[:, 1].max() - points[:, 1].min(),
+    }
+
+
 class Plotter:
 
     def __init__(self, paper, line_width=0, colour=[0, 0, 0, 1]):
@@ -174,6 +186,49 @@ class Plotter:
         self.line_to(self.paper.top_left())
         self.line_to(self.paper.bottom_left())
 
+    def draw_text(self, text, position, font='futural', height=10, x_scale=1,
+                  fit_width=None, fixed_height=True, spacing=None,
+                  v_align='baseline', h_align='left'):
+        x, y = position
+        hf = HersheyFonts()
+        hf.load_default_font(font)
+        hf.normalize_rendering(height)
+        hf.render_options['scaley'] *= -1
+        hf.render_options['scalex'] *= x_scale
+        if spacing is not None:
+            hf.render_options['spacing'] = spacing
+
+        hf.render_options['yofs'] -= hf.render_options['base_line']
+
+        metrics = _measure_text(hf, text)
+
+        if fit_width is not None:
+            hf.render_options['scalex'] *= fit_width / metrics['width']
+            hf.render_options['spacing'] *= fit_width / metrics['width']
+            metrics['x'] *= fit_width / metrics['width']
+            if not fixed_height:
+                hf.render_options['scaley'] *= fit_width / metrics['width']
+                metrics['y'] *= fit_width / text_width
+                metrics['height'] *= fit_width / metrics['width']
+            metrics['width'] = fit_width
+
+        if h_align == 'centre':
+            x -= metrics['width'] / 2
+        elif h_align == 'right':
+            x -= metrics['width']
+
+        x -= metrics['x']
+
+        if v_align == 'bottom':
+            y -= metrics['y'] + metrics['height']
+        elif v_align == 'top':
+            y -= metrics['y']
+
+        for s in hf.strokes_for_text(text):
+            self.move_to((s[0][0] + x, s[0][1] + y))
+            for p in s[1:]:
+                self.line_to((p[0] + x, p[1] + y))
+
 
 class SVGPlotter(Plotter):
 

requirements.txt

@@ -20,6 +20,7 @@ executing==1.2.0
 fastjsonschema==2.16.2
 fonttools==4.38.0
 fqdn==1.5.1
+Hershey-Fonts==2.1.0
 idna==3.4
 ipykernel==6.19.2
 ipython==8.7.0