Extract draw helpers; dedup cursor/thumbnail

src/eyetrax/app/demo.py

@@ -12,6 +12,7 @@ from eyetrax.calibration import (
 from eyetrax.cli import parse_common_args
 from eyetrax.filters import KalmanSmoother, KDESmoother, NoSmoother, make_kalman
 from eyetrax.gaze import GazeEstimator
+from eyetrax.utils.draw import draw_cursor, make_thumbnail
 from eyetrax.utils.screen import get_screen_size
 from eyetrax.utils.video import camera, fullscreen, iter_frames
 
@@ -85,28 +86,9 @@ def run_demo():
                 cv2.drawContours(canvas, contours, -1, (15, 182, 242), 5)
 
             if x_pred is not None and y_pred is not None and cursor_alpha > 0:
-                overlay = canvas.copy()
-                cv2.circle(overlay, (x_pred, y_pred), 30, (0, 0, 255), -1)
-                cv2.circle(overlay, (x_pred, y_pred), 25, (255, 255, 255), -1)
-                cv2.addWeighted(
-                    overlay,
-                    cursor_alpha * 0.6,
-                    canvas,
-                    1 - cursor_alpha * 0.6,
-                    0,
-                    canvas,
-                )
+                draw_cursor(canvas, x_pred, y_pred, cursor_alpha)
 
-            small = cv2.resize(frame, (cam_width, cam_height))
-            thumb = cv2.copyMakeBorder(
-                small,
-                BORDER,
-                BORDER,
-                BORDER,
-                BORDER,
-                cv2.BORDER_CONSTANT,
-                value=(255, 255, 255),
-            )
+            thumb = make_thumbnail(frame, size=(cam_width, cam_height), border=BORDER)
             h, w = thumb.shape[:2]
             canvas[-h - MARGIN : -MARGIN, -w - MARGIN : -MARGIN] = thumb
 

src/eyetrax/app/virtualcam.py

@@ -10,6 +10,7 @@ from eyetrax.calibration import (
 from eyetrax.cli import parse_common_args
 from eyetrax.filters import KalmanSmoother, KDESmoother, NoSmoother, make_kalman
 from eyetrax.gaze import GazeEstimator
+from eyetrax.utils.draw import draw_cursor
 from eyetrax.utils.screen import get_screen_size
 from eyetrax.utils.video import camera, iter_frames
 
@@ -73,7 +74,15 @@ def run_virtualcam():
                 if contours:
                     cv2.drawContours(output, contours, -1, (0, 0, 255), 3)
                 if x_pred is not None and y_pred is not None:
-                    cv2.circle(output, (x_pred, y_pred), 10, (0, 0, 255), -1)
+                    draw_cursor(
+                        output,
+                        x_pred,
+                        y_pred,
+                        alpha=1.0,
+                        radius_outer=10,
+                        radius_inner=0,
+                        color_outer=(0, 0, 255),
+                    )
 
                 cam.send(output)
                 cam.sleep_until_next_frame()

src/eyetrax/utils/draw.py

@@ -0,0 +1,46 @@
+from __future__ import annotations
+
+import cv2
+import numpy as np
+
+
+def draw_cursor(
+    canvas,
+    x: int,
+    y: int,
+    alpha: float,
+    *,
+    radius_outer: int = 30,
+    radius_inner: int = 25,
+    color_outer: tuple[int, int, int] = (0, 0, 255),
+    color_inner: tuple[int, int, int] = (255, 255, 255),
+):
+    if alpha <= 0.0:
+        return canvas
+
+    overlay = canvas.copy()
+    cv2.circle(overlay, (int(x), int(y)), radius_outer, color_outer, -1)
+    if radius_inner > 0:
+        cv2.circle(overlay, (int(x), int(y)), radius_inner, color_inner, -1)
+
+    cv2.addWeighted(overlay, alpha * 0.6, canvas, 1 - alpha * 0.6, 0, canvas)
+    return canvas
+
+
+def make_thumbnail(
+    frame,
+    *,
+    size: tuple[int, int] = (320, 240),
+    border: int = 2,
+    border_color: tuple[int, int, int] = (255, 255, 255),
+):
+    img = cv2.resize(frame, size)
+    return cv2.copyMakeBorder(
+        img,
+        border,
+        border,
+        border,
+        border,
+        cv2.BORDER_CONSTANT,
+        value=border_color,
+    )