Virtual devices should encode frames as PNG

Because, the virtual world is too perfect to JPEG. Lossy is obvious in the
virtual world. Lossless is expected and actually encodes really well for
this type of frame, so no down-side.

Author: acu192

auto/camera.py

@@ -15,6 +15,7 @@
 This is a **synchronous** interface.
 """
 
+import os
 import cv2
 import base64
 import numpy as np
@@ -23,6 +24,9 @@
 from auto.capabilities import list_caps, acquire, release
 
 
+IS_VIRTUAL = os.environ.get('MAI_IS_VIRTUAL', 'False').lower() in ['true', 't', '1', 'yes', 'y']
+
+
 class _CameraRGB:
     def __init__(self, camera):
         self._camera = camera
@@ -141,7 +145,11 @@ def base64_encode_image(frame):
             raise Exception("invalid number of channels")
     else:
         raise Exception("invalid frame ndarray ndim")
-    jpg_img = cv2.imencode('.jpg', frame, [cv2.IMWRITE_JPEG_QUALITY, 50])[1].tobytes()
-    base64_img = 'data:image/jpeg;base64,' + base64.b64encode(jpg_img).decode('ascii')
+    if IS_VIRTUAL:
+        png_img = cv2.imencode('.png', frame, [cv2.IMWRITE_PNG_COMPRESSION, 6])[1].tobytes()
+        base64_img = 'data:image/png;base64,' + base64.b64encode(png_img).decode('ascii')
+    else:
+        jpg_img = cv2.imencode('.jpg', frame, [cv2.IMWRITE_JPEG_QUALITY, 50])[1].tobytes()
+        base64_img = 'data:image/jpeg;base64,' + base64.b64encode(jpg_img).decode('ascii')
     return base64_img
 

auto/frame_streamer.py

@@ -175,7 +175,7 @@ def stream(frame, to_console=True, to_labs=False, verbose=False):
         rect = [0, 0, 0, 0]
         console.stream_image(rect, shape, final_frame.tobytes())
 
-    # Convert the frame to a JPG buffer and publish to the network connection.
+    # Encode the frame and publish to the network connection.
     if to_labs:
         base64_img = base64_encode_image(frame)
         send_message_to_labs({'base64_img': base64_img})