Initial commit

openflexure_microscope/__init__.py

@@ -0,0 +1 @@
+__version__ = "0.1.0"

openflexure_microscope/api/app.py

@@ -0,0 +1,175 @@
+#!/usr/bin/env python
+#TODO: Completely rewrite for new version of StreamingCamera
+from pprint import pprint
+from importlib import import_module
+import time, datetime
+
+from flask import Flask, render_template, Response, redirect, request, jsonify, send_file
+#import yaml
+import numpy as np
+
+# Raspberry Pi camera module (requires picamera package)
+#from camera.pi import Camera
+from openflexure_microscope.camera.pi import StreamingCamera
+
+app = Flask(__name__)
+cam = StreamingCamera()
+
+def parse_payload(request):
+    # TODO: Try-except for invalid JSON payloads
+    state = request.get_json()
+    return state
+
+def gen(camera):
+    """Video streaming generator function."""
+    while True:
+        # the obtained frame is a jpeg
+        frame = camera.get_frame()
+
+        yield (b'--frame\r\n'
+               b'Content-Type: image/jpeg\r\n\r\n' + frame + b'\r\n')
+
+@app.route('/')
+def index():
+    '''
+    Video streaming home page.
+    '''
+    cam.start_worker()  # Start the stream
+    return render_template('index.html')
+
+@app.route('/stream')
+def stream():
+    '''
+    Video streaming route. Put this in the src attribute of an img tag.
+    '''
+    return Response(gen(cam), mimetype='multipart/x-mixed-replace; boundary=frame')
+
+
+#TODO: Be able to change the image resolution with an option
+@app.route('/capture/', methods=['GET', 'POST', 'PUT'])
+def capture():
+    '''
+    POST/PUT: Capture a single image
+    GET: Return capture status, or download latest capture
+
+    Eg. curl http://192.168.1.140:5000/capture/ -H "Content-Type: application/json" -d '{"store":true}' -X POST
+    '''
+    if request.method == 'POST' or request.method == 'PUT':
+        state = parse_payload(request)
+        print(state)
+
+        # Handle filename argument
+        if 'filename' in state:
+            filename = state['filename']
+        else:
+            filename = None
+        
+        if 'write_to_file' in state:
+            write_to_file = bool(state['write_to_file'])
+        else:
+            write_to_file = False
+
+        if 'use_video_port' in state:
+            use_video_port = bool(state['use_video_port'])
+        else:
+            use_video_port = False
+        
+        if 'resize' in state:
+            resize_h = int(state['resize'])
+            resize_w = int(resize_h*(4/3))
+            resize = (resize_w, resize_h)
+        else:
+            resize = None
+
+        response = cam.capture(
+            write_to_file=write_to_file, 
+            use_video_port=use_video_port,
+            filename=filename,
+            resize=resize)
+
+        return str(response) + "\n"
+
+    else:  # If GET request
+
+        download = request.args.get('download')
+
+        state = cam.state
+        
+        if (download == 'true' or download == 'True' or download =='1') and cam.image is not None:
+            return send_file(cam.image.data, mimetype='image/jpeg')
+        else:
+            return jsonify(state)
+
+@app.route('/record/', methods=['GET', 'POST', 'PUT'])
+def record():
+    '''
+    POST/PUT: Start or stop a video recording
+    GET: Return recording status, or download latest recording
+
+    Eg. 
+    curl http://192.168.1.140:5000/record/ -H "Content-Type: application/json" -d '{"status":true}' -X POST
+    curl http://192.168.1.140:5000/record/ -H "Content-Type: application/json" -d '{"status":false}' -X POST
+    '''
+    if request.method == 'POST' or request.method == 'PUT':
+        state = request.get_json()
+        print(state)
+
+        # Handle filename argument
+        if 'filename' in state:
+            filename = state['filename']
+        else:
+            filename = None
+
+        # Handle status argument
+        if 'status' in state:
+            status = bool(state['status'])
+
+        # synchronise the arduino_time
+        if status == True:
+            response = cam.start_recording(filename=filename)
+            return str(response)
+
+        elif status == False:
+            response = cam.stop_recording()
+            return str(response)
+    
+    else:
+        download = request.args.get('download')
+
+        state = cam.state
+        
+        if (download == 'true' or download == 'True' or download =='1') and cam.state_record['recent'] is not None:
+            return send_file(cam.state_record['recent'],
+                mimetype='video/H264',
+                as_attachment=True)
+        else:
+            return jsonify(state)
+
+@app.route('/preview/', methods=['GET', 'POST', 'PUT'])
+def preview():
+    '''
+    POST/PUT: Start or stop the direct-to-GPU camera preview on the Pi
+    GET: Return preview status
+    '''
+    if request.method == 'POST' or request.method == 'PUT':
+        state = request.get_json()
+        print(state)
+
+        if 'status' in state:
+            status = bool(state['status'])
+
+        if status == False:
+            response = cam.stop_preview()
+        else:
+            response = cam.start_preview()
+
+        return str(response)
+    
+    else:
+        # Get args passed via URL (not useful here. Just for reference.)
+        state = cam.state
+        return jsonify(state)
+
+
+if __name__ == '__main__':
+    app.run(host='0.0.0.0', threaded=True, debug=True, use_reloader=False)

openflexure_microscope/api/templates/index.html

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+<html>
+  <head>
+    <title>Video Streaming Demonstration</title>
+  </head>
+  <body>
+    <h1>Video Streaming Demonstration</h1>
+    <img src="{{ url_for('stream') }}">
+  </body>
+</html>

openflexure_microscope/camera/__init__.py

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+from . import pi, base

openflexure_microscope/camera/base.py

@@ -0,0 +1,275 @@
+import time
+import os
+import io
+import threading
+import copy
+import datetime
+from PIL import Image
+
+try:
+    from greenlet import getcurrent as get_ident
+except ImportError:
+    try:
+        from thread import get_ident
+    except ImportError:
+        from _thread import get_ident
+
+# Slightly crappy debugger logging
+DEBUG = True
+
+def log(s):
+    if DEBUG:
+        print('DEBUG: {}'.format(s))
+
+
+class StreamObject(object):
+    def __init__(self, write_to_file: bool=None, filename: str=None, folder: str=None, fmt: str='file') -> None:
+        # Store a nice ID
+        self.id = filename
+        log("Created {}".format(self.id))
+
+        # Create file name
+        self.file = self.build_file_path(filename, folder, fmt)
+
+        # Byte stream properties
+        self.stream = io.BytesIO()  # Byte stream that data will be written to
+
+        # Set default write target
+        self.write_to_file = write_to_file
+        if self.write_to_file == False:
+            log("Default target for {} set to 'stream'".format(self.id))
+            self.target = self.stream
+        else:
+            log("Default target for {} set to 'file'".format(self.id))
+            self.target = self.file
+
+        # Object lock
+        self.locked = False  # Is the StreamObject locked for writing? (Handled by StreamingCamera)
+
+    def __enter__(self):
+        log("Entering context for {}. Stored files will be cleaned up automatically.".format(self.id))
+        return self
+
+    def __exit__(self, *args):
+        log("Cleaning up {}".format(self.id))
+        self.delete()
+
+    def build_file_path(self, filename: str, folder: str, fmt: str) -> str:
+        """
+        Construct a full file path, based on filename, folder, and file format. Defaults to datestamp
+        """
+        if filename:
+            file_name = "{}.{}".format(filename, fmt)
+        else:
+            file_name = "{}.{}".format(datetime.datetime.now().strftime("%Y-%m-%d_%H-%M-%S"), fmt)
+
+        # Create folder and file 
+        if folder:
+            if not os.path.exists(folder):
+                os.mkdir(folder)
+
+            file_path = os.path.join(folder, file_name)
+        else:
+            file_path = file_name
+        
+        return file_path
+    
+    def lock(self):
+        """Set locked flag to True"""
+        self.locked = True
+    
+    def unlock(self):
+        """Set locked flag to False"""
+        self.locked = False
+
+    @property
+    def data(self) -> io.BytesIO:
+        """Return a byte string of the capture data"""
+        self.stream.seek(0)  # Rewind the data bytes for reading
+
+        if not self.stream.getvalue() and os.path.isfile(self.file):  # If stream is empty but file is not
+            log("No stream data. Opening from file {}".format(self.file))
+            with open(self.file, 'rb') as f:
+                self.stream = io.BytesIO(f.read())  # Load bytes from file in disk
+            self.stream.seek(0)  # Rewind data bytes again
+        
+        data = self.stream.getbuffer()  # Create a copy of the stream bytes
+
+        return io.BytesIO(data)  # Read and return bytes data
+
+    @property
+    def binary(self) -> bytes:
+        """Return a byte string of the capture data"""
+        return self.data.getvalue()
+
+    def save(self):
+        """
+        Creates/opens a file, and writes this StreamObjects bytestring to the file.
+        """
+        with open(self.file, 'ab') as f:  # Load file as bytes
+            log("Writing stream to file {}".format(self.file))
+            f.seek(0, 0)  # Seek to the start of the file
+            f.write(self.binary)  # Write data bytes to file
+
+    def delete(self) -> bool:
+        """
+        If the StreamObject has been saved to disk, deletes the file and returns True.
+        """
+        if os.path.isfile(self.file):
+            log("Deleting file {}".format(self.file))
+            os.remove(self.file)
+            return True
+        else:
+            log("File not found {}".format(self.file))
+            return False
+
+
+class CameraEvent(object):
+    """An Event-like class that signals all active clients when a new frame is
+    available.
+    """
+    def __init__(self):
+        self.events = {}
+
+    def wait(self, timeout: int=5):
+        """Invoked from each client's thread to wait for the next frame."""
+        ident = get_ident()
+        if ident not in self.events:
+            # this is a new client
+            # add an entry for it in the self.events dict
+            # each entry has two elements, a threading.Event() and a timestamp
+            self.events[ident] = [threading.Event(), time.time()]
+        return self.events[ident][0].wait(timeout)
+
+    def set(self):
+        """Invoked by the camera thread when a new frame is available."""
+        now = time.time()
+        remove = None
+        for ident, event in self.events.items():
+            if not event[0].isSet():
+                # if this client's event is not set, then set it
+                # also update the last set timestamp to now
+                event[0].set()
+                event[1] = now
+            else:
+                # if the client's event is already set, it means the client
+                # did not process a previous frame
+                # if the event stays set for more than 5 seconds, then assume
+                # the client is gone and remove it
+                if now - event[1] > 5:
+                    remove = ident
+        if remove:
+            del self.events[remove]
+
+    def clear(self):
+        """Invoked from each client's thread after a frame was processed."""
+        self.events[get_ident()][0].clear()
+
+
+class BaseCamera(object):
+    thread = None  # Background thread that reads frames from camera
+    camera = None  # Camera object, for direct access to camera
+
+    frame = None  # Current frame is stored here by background thread
+    last_access = 0  # Time of last client access to the camera
+    event = CameraEvent()
+    
+    def __init__(self):
+        self.start_worker()
+
+        # Stores state of StreamingCamera
+        self.state = {
+        }
+
+    def start_worker(self, timeout: int=5) -> bool:
+        """Start the background camera thread if it isn't running yet."""
+        timeout_time = time.time() + timeout
+
+        self.last_access = time.time()
+        self.stop = False
+        
+        if self.thread is None:
+            # start background frame thread
+            self.thread = threading.Thread(target=self._thread)
+            self.thread.start()
+
+            # wait until frames are available
+            log("Waiting for frames")
+            while self.get_frame() is None:
+                if time.time() > timeout_time:
+                    raise TimeoutError("Timeout waiting for frames.")
+                    break
+                else:
+                    time.sleep(0)
+        return True
+
+    def stop_worker(self, timeout: int=5) -> bool:
+        """Flags worker thread for stop. Waits for thread to close, or times out."""
+        timeout_time = time.time() + timeout
+
+        self.stop = True
+        while self.thread:
+            if time.time() > timeout_time:
+                raise TimeoutError("Timeout waiting for worker thread to close.")
+                break
+            else:
+                time.sleep(0)
+        return True
+
+    def get_frame(self):
+        """Return the current camera frame."""
+        self.last_access = time.time()
+
+        # wait for a signal from the camera thread
+        self.event.wait()
+        self.event.clear()
+
+        return self.frame
+
+    def frames(self):
+        """Generator that returns frames from the camera."""
+        raise RuntimeError('Must be implemented by subclasses.')
+
+    def close(self):
+        """Handles closing the StreamingCamera"""
+        self.stop_worker()
+
+    def __enter__(self):
+        return self
+
+    def __exit__(self, exc_type, exc_value, traceback):
+        """Close camera stream on context exit."""
+        self.close()
+
+    def _thread(self):
+        """Camera background thread."""
+        self.frames_iterator = self.frames()
+
+        # Update state
+        self.state['stream_active'] = True
+
+        for frame in self.frames_iterator:
+            self.frame = frame
+            self.event.set()  # send signal to clients
+            time.sleep(0)
+
+            # if there hasn't been any clients asking for frames in
+            # the last 10 seconds then stop the thread
+            if time.time() - self.last_access > 20:
+                 self.frames_iterator.close()
+                 break
+            
+            try:
+                if self.stop is True:
+                    self.frames_iterator.close()
+                    break
+                    
+            except AttributeError:
+                pass
+    
+        # Reset thread
+        self.thread = None
+        # Destroy any stored camera object (used especially for handling Pi cameras)
+        self.camera = None
+        # Update state
+        self.state['stream_active'] = False

openflexure_microscope/camera/config.py

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+import yaml
+
+TYPES = {
+    'stream_resolution': tuple,
+    'video_resolution': tuple,
+    'image_resolution': tuple,
+    'numpy_resolution': tuple,
+    'jpeg_quality': int,
+    'framerate': int,
+    'awb_mode': str,
+    'red_gain': float,
+    'blue_gain': float,
+    'shutter_speed': int,
+    'saturation': int,
+    'analog_gain': float,
+    'digital_gain': float,
+}
+
+def convert_config(config):
+    """Convert datatype of config based on type dictionary"""
+    global TYPES
+
+    for key in config:
+        if key in TYPES:
+            config[key] = TYPES[key](config[key])  
+    
+    return config
+
+def load_config(yaml_path):
+    with open(yaml_path) as config_file:
+        return convert_config(yaml.load(config_file))
+
+if __name__ == "__main__":
+    from pprint import pprint
+
+    config = load_config('config_picamera.yaml')
+    pprint(config)

openflexure_microscope/camera/config_picamera.yaml

@@ -0,0 +1,35 @@
+# Exposure mode
+exposure_mode: 'off'
+
+# The analog gain offers higher sensitivity and less noise than using digital gain only
+analog_gain: 1.
+digital_gain: 1.
+
+# When queried, the shutter_speed property returns the shutter speed of the camera in microseconds, 
+# or 0 which indicates that the speed will be automatically determined.
+# If high value does not work, need to decrease the fps for streaming
+shutter_speed: 30000
+
+# Auto white balance: The red and blue values are returned Fraction instances. 
+# The values will be between 0.0 and 8.0.
+awb_mode: 'off'
+
+# If not using auto, then you can change the awb_gains
+red_gain: 1.3
+blue_gain: 1.2
+
+# Color saturation of the camera as an integer between -100 and 100. 
+saturation: 0
+
+# ISO Valid values are between 0 (auto) and 800 (1600 is not available?). 
+# ISO value is not used anyway as we are fixing the gains
+iso: 500
+
+# Resolutions for streaming and capture
+video_resolution: [832, 624]
+image_resolution: [2592, 1944]
+numpy_resolution: [1312, 976]
+
+# Capture quality
+jpeg_quality: 75
+framerate: 24

openflexure_microscope/camera/pi.py

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+# -*- coding: utf-8 -*-
+"""
+Raspberry Pi camera implementation of the StreamingCamera class.
+
+NOTES:
+Still port used for image capture
+Preview port reserved for onboard GPU preview
+Video port:
+    Splitter port 0: Image capture (if use_video_port == True)
+    Splitter port 1: Streaming frames
+    Splitter port 2: Video capture
+    Splitter port 3: [Currently unused]
+
+StreamingCamera streams at video_resolution
+Camera capture resolution set to video_resolution in frames()
+Video port uses that resolution for everything. If a different resolution
+is specified for video capture, this is handled by the resizer. 
+
+Still capture (if use_video_port == False) uses pause_stream_for_capture
+to temporarily increase the capture resolution.
+"""
+
+from __future__ import division
+
+import io
+import time
+import datetime
+import sys
+import os
+import yaml
+import copy
+import numpy as np
+from PIL import Image
+
+# Pi camera
+import picamera
+import picamera.array
+
+# Type hinting
+from typing import Tuple
+
+# Threading
+import threading
+
+from .base import BaseCamera, StreamObject, log
+# Richard's fix gain
+from .set_picamera_gain import set_analog_gain, set_digital_gain
+# Manage config
+from .config import load_config
+
+HERE = os.path.abspath(os.path.dirname(__file__))
+DEFAULT_CONFIG = os.path.join(HERE, 'config_picamera.yaml')
+
+class StreamingCamera(BaseCamera):
+
+    def __init__(self):
+        # Capture data
+        self.image = None
+        self.video = None
+
+        # Camera settings
+        self.settings = {
+            'video_resolution': (832, 624),
+            'image_resolution': (2592, 1944),
+            'numpy_resolution': (1312, 976),
+            'jpeg_quality': 75,
+        }
+
+        # Store state of StreamingCamera
+        self.state = {
+            'video_recent': None,
+            'image_recent': None,
+            'stream_active': False,
+            'record_active': False,
+            'preview_active': False,
+        }
+
+        # Finally, run BaseCamera init to start thread
+        BaseCamera.__init__(self)
+
+    def initialisation(self):
+        pass
+
+    def start_preview(self) -> bool:
+        """Function to start the onboard GPU camera preview."""
+        self.start_worker()
+
+        self.camera.start_preview()
+        self.state['preview_active'] = True
+        return True
+
+    def stop_preview(self) -> bool:
+        """Function to start the onboard GPU camera preview."""
+        self.start_worker()
+
+        self.camera.stop_preview()
+        self.state['preview_active'] = False
+        return True
+
+    # TODO: Handle exceptions
+    def update_settings(self, config_path: str=None) -> None:
+        """
+        Opens config_picamera.yaml file and writes valid settings
+        to the camera hardware object
+        """
+        global DEFAULT_CONFIG
+        
+        self.start_worker()
+
+        if not config_path:
+            config = load_config(DEFAULT_CONFIG)
+        else:
+            config = load_config(config_path)
+
+        log("Applying config:")
+        log(config)
+
+        # StreamingCamera settings
+        if 'video_resolution' in config:
+            self.settings['video_resolution'] = config['video_resolution']
+        if 'image_resolution' in config:
+            self.settings['image_resolution'] = config['image_resolution']
+        if 'numpy_resolution' in config:
+            self.settings['numpy_resolution'] = config['numpy_resolution']
+
+        if 'jpeg_quality' in config:
+            self.settings['jpeg_quality'] = config['jpeg_quality']
+        if 'framerate' in config:
+            self.settings['framerate'] = config['framerate']
+
+        # Camera AWB
+        if 'awb_mode' in config:
+            self.camera.awb_mode = config['awb_mode']
+        if 'red_gain' in config and 'blue_gain' in config:
+            self.camera.awb_gains = (config['red_gain'], config['blue_gain'])
+
+        # Camera framerate
+        if 'framerate' in config:
+            self.camera.framerate = config['framerate']
+        # Camera exposure
+        if 'shutter_speed' in config:
+            self.camera.shutter_speed = config['shutter_speed']
+        if 'saturation' in config:
+            self.camera.saturation = config['saturation']
+        # Camera misc.
+        self.camera.led = False
+        # Richard's library to set analog and digital gains
+        if 'analog_gain' in config:
+            set_analog_gain(self.camera, config['analog_gain'])
+        if 'digital_gain' in config:
+            set_digital_gain(self.camera, config['digital_gain'])
+
+    # TODO: Rewrite this bit?
+    # https://picamera.readthedocs.io/en/release-1.13/api_camera.html
+    def change_zoom(self, zoom_value: int=1) -> None:
+        """Change the camera zoom, handling recentering and scaling."""
+        zoom_value = float(zoom_value)
+        if zoom_value < 1:
+            zoom_value = 1
+        # Richard's code for zooming !
+        fov = self.camera.zoom
+        centre = np.array([fov[0] + fov[2]/2.0, fov[1] + fov[3]/2.0])
+        size = 1.0/zoom_value
+        # If the new zoom value would be invalid, move the centre to
+        # keep it within the camera's sensor (this is only relevant 
+        # when zooming out, if the FoV is not centred on (0.5, 0.5)
+        for i in range(2):
+            if np.abs(centre[i] - 0.5) + size/2 > 0.5:
+                centre[i] = 0.5 + (1.0 - size)/2 * np.sign(centre[i]-0.5)
+        print("setting zoom, centre {}, size {}".format(centre, size))
+        new_fov = (centre[0] - size/2, centre[1] - size/2, size, size)
+        self.camera.zoom = new_fov
+
+    def stop_recording(self, target=None) -> bool:
+        """Stop the last started video recording on splitter port 2.
+
+        target (str/BytesIO): Target object to write data bytes to.
+        """
+        if not target:  # If no target is defined
+            target_obj = self.video  # Assume StreamingCamera as target
+            target_obj.unlock()  # Unlock the StreamObject
+        else:
+            target_obj = target
+
+        # Stop the camera video recording on port 2
+        log("Stopping recording")
+        self.camera.stop_recording(splitter_port=2)
+        log("Recording stopped")
+
+        # Update state dictionary
+        self.state['record_active'] = False
+        self.state['video_recent'] = str(target_obj)
+
+        return True
+
+    def start_recording(
+            self,
+            target=None,
+            write_to_file: bool=True,
+            filename: str=None,
+            folder: str='record',
+            fmt: str='h264',
+            quality: int=15):
+        """Start a new video recording, writing to a target object.
+
+        target (str/BytesIO): Target object to write bytes to (default StreamObject)
+        write_to_file (bool/NoneType): Should the StreamObject write to a file? (default True for video capture)
+        filename (str): Name of the stored file (defaults to timestamp)
+        folder (str): Relative directory to store data file in.
+        fmt (str): Format of the capture (default 'h264')
+        """
+        self.start_worker()
+
+        # If no target is specified, store to StreamingCamera
+        if not target:
+            if (self.video is None) or (not self.video.locked):  # If target is not locked
+
+                self.video = StreamObject(write_to_file=write_to_file, filename=filename, folder=folder, fmt=fmt)  # Reset/create StreamObject
+
+                target = self.video.target  # Store to the StreamObject BytesIO
+                target_obj = self.video  # Note the target StreamObject, used for function return
+
+                target_obj.lock()  # Lock the StreamObject while recording
+
+            else:
+                print("Cannot start recording a new video until the current recording has been stopped. Returning None.")
+                return None
+        else:
+            target_obj = target
+
+        # Start the camera video recording on port 2
+        log("Starting record at {}".format(self.settings['video_resolution']))
+        self.camera.start_recording(
+            target,
+            format=fmt,
+            splitter_port=2,
+            resize=self.settings['video_resolution'],
+            quality=quality)
+       
+        # Update state dictionary
+        self.state['record_active'] = True
+
+        return target_obj
+
+    def pause_stream_for_capture(self, splitter_port: int=1, resolution: Tuple[int, int]=None) -> None:
+        """
+        Pause capture on a splitter port.
+
+        splitter_port (int): Splitter port to stop recording on
+        resolution ((int, int)): Resolution to set the camera to, after stopping recording.
+        """
+        log("Pausing stream")
+        # If no resolution is specified, default to image_resolution
+        if not resolution:
+            resolution = self.settings['image_resolution']
+
+        # Stop the camera video recording on port 1
+        self.camera.stop_recording(splitter_port=splitter_port)
+
+        # Increase the resolution for taking an image
+        self.camera.resolution = resolution
+
+    def resume_stream_for_capture(self, splitter_port: int=1, resolution: Tuple[int, int]=None) -> None:
+        """
+        Resume capture on a splitter port
+
+        splitter_port (int): Splitter port to start recording on
+        resolution ((int, int)): Resolution to set the camera to, before starting recording.
+        """
+        log("Unpausing stream")
+        if not resolution:
+            resolution = self.settings['video_resolution']
+
+        # Reduce the resolution for video streaming
+        self.camera.resolution = resolution
+
+        # Resume the video channel
+        self.camera.start_recording(
+            self.stream,
+            format='mjpeg',
+            quality=self.settings['jpeg_quality'],
+            splitter_port=splitter_port)
+
+    def capture(
+            self,
+            target=None,
+            write_to_file: bool=False,
+            use_video_port: bool=False,
+            filename: str=None,
+            folder: str='capture',
+            fmt: str='jpeg',
+            resize: Tuple[int, int]=None):
+        """
+        Captures a still image to a StreamObject.
+
+        Defaults to JPEG format.
+        Target object can be overridden for development purposes.
+
+        target (str/BytesIO): Target object to write data bytes to
+        write_to_file (bool): Should the StreamObject write to a file, instead of BytesIO stream?
+        use_video_port (bool): Capture from the video port used for streaming (lower resolution, faster)
+        filename (str): Name of the stored file (defaults to timestamp)
+        folder (str): Relative directory to store data file in.
+        fmt (str): Format of the capture (default 'h264')
+        resize ((int, int)): Resize the captured image.
+        """
+        self.start_worker()
+
+        # If no target is specified, store to StreamingCamera
+        if not target:
+            self.image = StreamObject(write_to_file=write_to_file, filename=filename, folder=folder, fmt=fmt)  # Reset StreamObject
+
+            target = self.image.target  # Store to the StreamObject BytesIO
+            target_obj = self.image  # Note the target StreamObject, used for function return
+
+        else:
+            target_obj = target
+
+        log("Capturing to {}".format(target))
+
+        if not use_video_port:
+
+            # Pause video splitter port 1
+            self.pause_stream_for_capture()
+
+            self.camera.capture(
+                target,
+                format=fmt,
+                quality=100,
+                resize=resize,
+                bayer=True)
+
+            # Resume video splitter port 1
+            self.resume_stream_for_capture()
+
+        else:
+            self.camera.capture(
+                target,
+                format=fmt,
+                quality=100,
+                resize=resize,
+                bayer=False,
+                use_video_port=True)
+
+        # Update state dictionary
+        self.state['image_recent'] = str(target_obj)
+
+        return target_obj
+
+    def array(self, rgb=False, use_video_port: bool=True, resize: Tuple[int, int]=None) -> np.ndarray:
+        """Captures an uncompressed still YUV image to a Numpy array.
+
+        use_video_port (bool): Capture from the video port used for streaming (lower resolution, faster)
+        resize ((int, int)): Resize the captured image.
+        """
+        self.start_worker()
+
+        if use_video_port:
+            resolution = self.settings['video_resolution']
+        else:
+            resolution = self.settings['numpy_resolution']
+        
+        if resize:
+            size = resize
+        else:
+            size = resolution
+
+        if not use_video_port:
+            self.pause_stream_for_capture(resolution=resolution)
+        
+        log("Creating PiYUVArray")
+        with picamera.array.PiYUVArray(self.camera, size=size) as output:
+            log("Capturing to PiYUVArray from {}".format(self.camera))
+
+            self.camera.capture(
+                output,
+                resize=size,
+                format='yuv',
+                use_video_port=use_video_port)
+
+            log("Capturing complete")
+
+            if not use_video_port:
+                self.resume_stream_for_capture()
+
+            if rgb:
+                log("Converting to RGB")
+                return output.rgb_array
+            else:
+                return output.array
+
+    def frames(self):
+        """
+        Create iterator used by worker thread to generate stream frames.
+
+        Holds a Pi camera in context, records video from port 1 to a 
+        byte stream, and iterates sequential frames.
+        """
+        # Run this initialisation method
+        self.initialisation()
+        self.stream_method = 'PiCamera'
+
+        with picamera.PiCamera() as self.camera:
+            # Let camera warm up
+            time.sleep(0.1)
+            # Settings config
+            self.update_settings()
+            # Set stream resolution
+            self.camera.resolution = self.settings['video_resolution']
+
+            # streaming
+            self.stream = io.BytesIO()
+
+            # start recording on video splitter port 1
+            self.camera.start_recording(
+                self.stream,
+                format='mjpeg',
+                quality=self.settings['jpeg_quality'],
+                splitter_port=1)
+            
+            while True:
+                # reset stream for next frame
+                self.stream.seek(0)
+                self.stream.truncate()
+                # to stream, read the new frame
+                time.sleep(1/self.settings['framerate']*0.1)
+                # yield the result to be read
+                frame = self.stream.getvalue()
+                # ensure the size of package is right
+                if len(frame) == 0:
+                    pass
+                else:
+                    yield frame

openflexure_microscope/camera/set_picamera_gain.py

@@ -0,0 +1,70 @@
+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...")
+
+