Add square-root scale mapping

web/app.py

@@ -8,7 +8,7 @@ from fontTools.pens.svgPathPen import SVGPathPen
 
 app = Flask(__name__)
 
-VERSION = "0.77"
+VERSION = "0.78"
 
 _LOGO_PATH = pathlib.Path(__file__).parent / 'static' / 'logo.png'
 _LOGO_B64 = base64.b64encode(_LOGO_PATH.read_bytes()).decode()
@@ -334,8 +334,8 @@ def _text_to_paths(text, x, y, font_size, anchor='start', fill='#1a1a1a', wrap_t
 
 
 def generate_svg(unit, min_val, max_val, range_label, big_ticks, small_ticks, label_count,
-                 use_paths=True, log_scale=False, custom_labels=None, label_size=9):
-    if log_scale:
+                 use_paths=True, scale_type='linear', custom_labels=None, label_size=9):
+    if scale_type == 'log':
         if min_val <= 0 or max_val <= 0:
             raise ValueError("Logarithmic scale requires min and max values greater than 0.")
         lmin, lmax = math.log(min_val), math.log(max_val)
@@ -348,6 +348,20 @@ def generate_svg(unit, min_val, max_val, range_label, big_ticks, small_ticks, la
 
         def major_value(i):
             return min_val * (max_val / min_val) ** (i / big_ticks)
+
+    elif scale_type == 'sqrt':
+        if min_val < 0:
+            raise ValueError("Square-root scale requires min value ≥ 0.")
+        span = max_val - min_val
+        if span <= 0:
+            raise ValueError("Square-root scale requires max value greater than min.")
+
+        def value_to_x(v):
+            return ZERO_X + SCALE_LEN * math.sqrt((v - min_val) / span)
+
+        def major_value(i):
+            return min_val + span * (i / big_ticks) ** 2
+
     else:
         span = max_val - min_val
 
@@ -357,7 +371,7 @@ def generate_svg(unit, min_val, max_val, range_label, big_ticks, small_ticks, la
             return ZERO_X + SCALE_LEN * (v - min_val) / span
 
         def major_value(i):
-            return min_val + (max_val - min_val) * i / big_ticks
+            return min_val + span * i / big_ticks
 
     big_interval = SCALE_LEN / big_ticks
     # Major ticks are always physically evenly spaced; only their values differ.
@@ -474,14 +488,14 @@ def generate():
     small_ticks = max(0, min(20, int(request.form.get('small_ticks', 4))))
     label_count = max(2, int(request.form.get('label_count', 6)))
     use_paths   = request.form.get('output_mode', 'paths') == 'paths'
-    log_scale   = request.form.get('scale_type', 'linear') == 'log'
+    scale_type  = request.form.get('scale_type', 'linear')
 
     custom_labels = [s.strip() for s in request.form.get('labels', '').split(',') if s.strip()] or None
     label_size    = max(0.5, min(25.0, float(request.form.get('label_size', 9))))
 
     try:
         svg = generate_svg(unit, min_val, max_val, range_label, big_ticks, small_ticks,
-                           label_count, use_paths, log_scale, custom_labels, label_size)
+                           label_count, use_paths, scale_type, custom_labels, label_size)
     except ValueError as err:
         return Response(str(err), status=400, mimetype='text/plain')
     return Response(svg, mimetype='image/svg+xml')