Use platform-independent method for getting font

model_server/base/annotators.py

 import numpy as np
+from matplotlib import font_manager
 from PIL import Image, ImageDraw, ImageFont
 
 from model_server.base.process import rescale
 
+def _get_font():
+    return ImageFont.truetype(
+        font_manager.findfont(
+            font_manager.FontProperties(
+                family='sans-serif',
+                weight='bold'
+            )
+        )
+    )
+
+
 def draw_boxes_on_3d_image(roiset, draw_full_depth=False, **kwargs):
     h, w, chroma, nz = roiset.acc_raw.shape
     font_size = kwargs.get('font_size', 18)
@@ -25,7 +37,7 @@ def draw_boxes_on_3d_image(roiset, draw_full_depth=False, **kwargs):
         for ci in range(0, len(channels)):
             pilimg = Image.fromarray(roiset.acc_raw.data[:, :, channels[ci], zi])
             draw = ImageDraw.Draw(pilimg)
-            draw.font = ImageFont.truetype(font="arial.ttf", size=font_size)
+            draw.font = _get_font()
 
             for roi in subset.itertuples('Roi'):
                 xm = round((roi.x0 + roi.x1) / 2)