Initial commit

openflexure_microscope/camera/set_picamera_gain.py

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+from __future__ import print_function
+
+import picamera
+from picamera import mmal, mmalobj, exc
+from picamera.mmalobj import to_rational
+import time
+
+
+MMAL_PARAMETER_ANALOG_GAIN = mmal.MMAL_PARAMETER_GROUP_CAMERA + 0x59
+MMAL_PARAMETER_DIGITAL_GAIN = mmal.MMAL_PARAMETER_GROUP_CAMERA + 0x5A
+
+def set_gain(camera, gain, value):
+    """Set the analog gain of a PiCamera.
+    
+    camera: the picamera.PiCamera() instance you are configuring
+    gain: either MMAL_PARAMETER_ANALOG_GAIN or MMAL_PARAMETER_DIGITAL_GAIN
+    value: a numeric value that can be converted to a rational number.
+    """
+    if gain not in [MMAL_PARAMETER_ANALOG_GAIN, MMAL_PARAMETER_DIGITAL_GAIN]:
+        raise ValueError("The gain parameter was not valid")
+    ret = mmal.mmal_port_parameter_set_rational(camera._camera.control._port, 
+                                                    gain,
+                                                    to_rational(value))
+    if ret == 4:
+        raise exc.PiCameraMMALError(ret, "Are you running the latest version of the userland libraries? Gain setting was introduced in late 2017.")
+    elif ret != 0:
+        raise exc.PiCameraMMALError(ret)
+
+def set_analog_gain(camera, value):
+    """Set the gain of a PiCamera object to a given value."""
+    set_gain(camera, MMAL_PARAMETER_ANALOG_GAIN, value)
+
+def set_digital_gain(camera, value):
+    """Set the digital gain of a PiCamera object to a given value."""
+    set_gain(camera, MMAL_PARAMETER_DIGITAL_GAIN, value)
+
+
+if __name__ == "__main__":
+    with picamera.PiCamera() as cam:
+        cam.start_preview(fullscreen=False, window=(0,50,640,480))
+        time.sleep(2)
+
+        # fix the auto white balance gains at their current values
+        g = cam.awb_gains
+        cam.awb_mode = "off"
+        cam.awb_gains = g
+
+        # fix the shutter speed
+        cam.shutter_speed = cam.exposure_speed
+
+        print("Current a/d gains: {}, {}".format(cam.analog_gain, cam.digital_gain))
+
+        print("Attempting to set analogue gain to 1")
+        set_analog_gain(cam, 1)
+        print("Attempting to set digital gain to 1")
+        set_digital_gain(cam, 1)
+        # The old code is left in here in case it is a useful example...
+        #ret = mmal.mmal_port_parameter_set_rational(cam._camera.control._port, 
+        #                                            MMAL_PARAMETER_DIGITAL_GAIN,
+        #                                            to_rational(1))
+        #print("Return code: {}".format(ret))
+
+        try:
+            while True:
+                print("Current a/d gains: {}, {}".format(cam.analog_gain, cam.digital_gain))
+                time.sleep(1)
+        except KeyboardInterrupt:
+            print("Stopping...")
+
+