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Software for Camera Control in Python
Hi folks, just wanted to share a library we have developed for controlling the camera (tested with picamera v2).
The library allows to set exposure time, gain and analogic gain.

Copyright (C) 2019 MVISIA

This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Library General Public
License as published by the Free Software Foundation; either
version 2 of the License, or (at your option) any later version.

This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
Library General Public License for more details.

You should have received a copy of the GNU Library General Public
License along with this library; if not, write to the
Free Software Foundation, Inc., 51 Franklin St, Fifth Floor,
Boston, MA  02110-1301, USA.


from gi.repository import Gst, GObject
src = Gst.ElementFactory.make('rkcamsrc') # rkcamsrc is a singleton and needs to be instantiated before importing cv2

import os
import time
import numpy as np
import logging
logging = logging.getLogger('server_log')
import glob
import cv2 as cv
from queue import Queue, Full

class IMX219:
    max_exposure = 4095
    min_exposure = 0
    max_gain = 43663.0
    min_gain = 256.0
    max_again = 2816.0
    min_again = 256.0
    max_height = 1050
    max_width = 1400

def unnorm(val, vmin, vmax):
    return int(round(val*(vmax - vmin)+vmin))

def norm(val, vmin, vmax):
    return (val-vmin)/(vmax-vmin)

def check_limits(val, vmin=None, vmax=None):
    if vmin is not None:
        if val < vmin:
            return True
    if vmax is not None:
        if val > vmax:
            return True
    return False

class MIPICamera():
    def __init__(self, width=1400, height=1050, cropx0=0, cropx1=0, cropy0=0, cropy1=0, buffer_size=2, exposure=None, gain=0.0, again=0.0):
        self.buffer_size = buffer_size
        self.queue = Queue(buffer_size)

        self.src = src
        self.setup_src(cropx0, cropx1, cropy0, cropy1)
        self.sink = Gst.ElementFactory.make('appsink')
        self.init_caps(width, height)

        # configure aec
        if exposure is None:
            self.src.props.isp_mode ='2A'
            self.src.props.isp_mode ='0A'
            gain = unnorm(gain, IMX219.min_gain, IMX219.max_gain)
            again = unnorm(again, IMX219.min_again, IMX219.max_again)
            exposure = np.clip(exposure*10, IMX219.min_exposure, IMX219.max_exposure)

            # always set analog gain before gain
            os.system('v4l2-ctl -d /dev/video0 -c analogue_gain=%d' % again)
            os.system('v4l2-ctl -d /dev/video0 -c gain=%d' % gain)
            os.system('v4l2-ctl -d /dev/video0 -c exposure=%d' % exposure)
  'V4L2-CTL: Exposure Time: %d, gain: %d, analogue_gain: %d' % (exposure, gain, again))


    def setup_src(self, cropx0, cropx1, cropy0, cropy1):
            self.src.props.output_crop = '%dx%dx%dx%d' % (cropx0, cropy0, cropx1, cropy1)
            self.src.props.input_crop = '%dx%dx%dx%d' % (cropx0, cropy0, cropx1, cropy1)
            self.src.props.device = '/dev/video0'
            self.src.props.io_mode = 4
            self.src.props.tuning_xml_path = '/etc/cam_iq/IMX219.xml'

    def init_caps(self, width, height):
        self.caps = Gst.ElementFactory.make('capsfilter')
        capsprop = Gst.caps_from_string('video/x-raw,format=NV12,width=%d,height=%d' %
                                        (width, height))
        if check_limits(width, vmax=IMX219.max_width) or check_limits(height, vmax=IMX219.max_height):
            raise PipelineCameraError('Max size is %dx%d' % (IMX219.max_height, IMX219.max_width))
        self.caps.set_property('caps', capsprop)
        self.pipeline = Gst.Pipeline()
        self.pipeline.add(self.src, self.caps, self.sink)
        src.link_filtered(self.sink, capsprop)

    def init_callbacks(self):
        self.sink.set_property('emit-signals', True)
        self.sink.set_property('sync', True)
        self.sink.connect('new-sample', self.on_sample, self.sink)
        self.bus = self.pipeline.get_bus()

    def close(self):

    def parse_sample(self, sample):
        buf = sample.get_buffer()
        caps = sample.get_caps().get_structure(0)
        f, h, w = caps.get_value('format'), caps.get_value('height'), caps.get_value('width')
        if f == 'NV12':
            img = np.ndarray((int(h*1.5), w, 1), buffer=buf.extract_dup(0, buf.get_size()), dtype=np.uint8)
            img = cv.cvtColor(img, cv.COLOR_YUV2BGR_NV12)
            return img
            raise ValueError('Unknown format')

    def on_sample(self, sink, data):
        sample = sink.emit('pull-sample')
            self.queue.put(self.parse_sample(sample), block=False) # DONT BLOCK THIS THREAD !!!
        except Full:
        return Gst.FlowReturn.OK

    def __call__(self):
            img = self.queue.get(timeout=2.5)
        except Full:
            raise PipelineCameraError('Camera capture failed')
        return img

if __name__ == '__main__':
    cam = MIPICamera()
    while True:
        img = cam()
        cv.imshow('win', img)
        if cv.waitKey(1) & 0xFF == ord('q'):

Best regards,
A great praise to you Smile
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