Picamera2 库 + TensorFlow Lite 实现实时对象检测

2022年5月16日 树莓派实验室 未分类 1

Raspberry Pi OS Bullseye 版本发布时弃用的 Picamera 以新面貌回归了，那就是 Picamera2 库。

下面介绍使用树莓派摄像头模块，用 Picamera2 库和 TensorFlow Lite 实现实时对象检测。

安装 Picamera2 库

因为目前 Picamera2 库还处于预览版，因此暂时只能通过 GitHub 编译安装。

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$ sudo apt update
 
$ sudo apt install -y libboost-dev
 
$ sudo apt install -y libgnutls28-dev openssl libtiff5-dev
 
$ sudo apt install -y qtbase5-dev libqt5core5a libqt5gui5 libqt5widgets5
 
$ sudo apt install -y meson
 
$ sudo pip3 install pyyaml ply
 
$ sudo pip3 install --upgrade meson
 
$ sudo apt install -y libglib2.0-dev libgstreamer-plugins-base1.0-dev
 
$ git clone --branch picamera2 https://github.com/raspberrypi/libcamera.git
 
$ cd libcamera
 
$ meson build --buildtype=release -Dpipelines=raspberrypi -Dipas=raspberrypi -Dv4l2=true -Dgstreamer=enabled -Dtest=false -Dlc-compliance=disabled -Dcam=disabled -Dqcam=enabled -Ddocumentation=disabled -Dpycamera=enabled
 
$ ninja -C build
 
$ sudo ninja -C build install
 
$ cd ~
 
$ git clone https://github.com/tomba/kmsxx.git
 
$ cd kmsxx
 
$ git submodule update --init
 
$ sudo apt install -y libfmt-dev libdrm-dev
 
$ meson build
 
$ ninja -C build
 
$ cd ~
 
$ sudo pip3 install pyopengl
 
$ sudo apt install python3-pyqt5
 
$ git clone https://git@github.com:raspberrypi/picamera2.git
 
$ sudo pip3 install opencv-python==4.4.0.46
 
$ sudo apt install -y libatlas-base-dev
 
$ sudo pip3 install numpy --upgrade
 
$ cd ~
 
$ git clone https://github.com/RaspberryPiFoundation/python-v4l2.git

要跑起来还需要设置 PYTHONPATH 运行环境。比如你需要将下面的内容添加到 .bashrc 文件中。

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export PYTHONPATH=/home/pi/picamera2:/home/pi/libcamera/build/src/py:/home/pi/kmsxx/build/py:/home/pi/python-v4l2

安装 TensorFlow Lite

由于我们将通过 Python 代码进行推理而不是训练，因此我们可以安装轻量级 TensorFlow Lite 运行时库以及我们需要的其他一些东西：

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$ sudo apt install build-essentials
 
$ sudo apt install git
 
$ sudo apt install libatlas-base-dev
 
$ sudo apt install python3-pip
 
$ pip3 install tflite-runtime
 
$ pip3 install opencv-python==4.4.0.46
 
$ pip3 install pillow
 
$ pip3 install numpy

开始使用 TensorFlow Lite

安装完所有东西之后，下面我们构建一个演示程序：寻找图像中的苹果和香蕉。

视频播放器

代码会启用摄像头，并将采集到的图像不断传给 TensorFlow 的图像缓冲区。TensorFlow 随之在图像上进行对象检测。如果检测到任何对象，将用矩形框进行标注。

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import tflite_runtime.interpreter as tflite
 
 
 
import sys
 
import os
 
import argparse
 
 
 
import cv2
 
import numpy as np
 
from PIL import Image
 
from PIL import ImageFont, ImageDraw
 
 
 
from qt_gl_preview import *
 
from picamera2 import *
 
 
 
normalSize = (640, 480)
 
lowresSize = (320, 240)
 
 
 
rectangles = []
 
 
 
def ReadLabelFile(file_path):
 
  with open(file_path, 'r') as f:
 
    lines = f.readlines()
 
  ret = {}
 
  for line in lines:
 
    pair = line.strip().split(maxsplit=1)
 
    ret[int(pair[0])] = pair[1].strip()
 
  return ret
 
 
 
def DrawRectangles(request):
 
   stream = request.picam2.stream_map["main"]
 
   fb = request.request.buffers[stream]
 
   with fb.mmap(0) as b:
 
       im = np.array(b, copy=False, dtype=np.uint8).reshape((normalSize[1],normalSize[0], 4))
 
 
 
       for rect in rectangles:
 
          print(rect)
 
          rect_start = (int(rect[0]*2) - 5, int(rect[1]*2) - 5)
 
          rect_end = (int(rect[2]*2) + 5, int(rect[3]*2) + 5)
 
          cv2.rectangle(im, rect_start, rect_end, (0,255,0,0))
 
          if len(rect) == 5:
 
            text = rect[4]
 
            font = cv2.FONT_HERSHEY_SIMPLEX
 
            cv2.putText(im, text, (int(rect[0]*2) + 10, int(rect[1]*2) + 10), font, 1, (255,255,255),2,cv2.LINE_AA)
 
       del im
 
 
 
def InferenceTensorFlow( image, model, output, label=None):
 
   global rectangles
 
 
 
   if label:
 
       labels = ReadLabelFile(label)
 
   else:
 
       labels = None
 
 
 
   interpreter = tflite.Interpreter(model_path=model, num_threads=4)
 
   interpreter.allocate_tensors()
 
 
 
   input_details = interpreter.get_input_details()
 
   output_details = interpreter.get_output_details()
 
   height = input_details[0]['shape'][1]
 
   width = input_details[0]['shape'][2]
 
   floating_model = False
 
   if input_details[0]['dtype'] == np.float32:
 
       floating_model = True
 
 
 
   rgb = cv2.cvtColor(image,cv2.COLOR_GRAY2RGB)
 
   initial_h, initial_w, channels = rgb.shape
 
 
 
   picture = cv2.resize(rgb, (width, height))
 
 
 
   input_data = np.expand_dims(picture, axis=0)
 
   if floating_model:
 
      input_data = (np.float32(input_data) - 127.5) / 127.5
 
 
 
   interpreter.set_tensor(input_details[0]['index'], input_data)
 
 
 
   interpreter.invoke()
 
 
 
   detected_boxes = interpreter.get_tensor(output_details[0]['index'])
 
   detected_classes = interpreter.get_tensor(output_details[1]['index'])
 
   detected_scores = interpreter.get_tensor(output_details[2]['index'])
 
   num_boxes = interpreter.get_tensor(output_details[3]['index'])
 
 
 
   rectangles = []
 
   for i in range(int(num_boxes)):
 
      top, left, bottom, right = detected_boxes[0][i]
 
      classId = int(detected_classes[0][i])
 
      score = detected_scores[0][i]
 
      if score > 0.5:
 
          xmin = left * initial_w
 
          ymin = bottom * initial_h
 
          xmax = right * initial_w
 
          ymax = top * initial_h
 
          box = [xmin, ymin, xmax, ymax]
 
          rectangles.append(box)
 
          if labels:
 
              print(labels[classId], 'score = ', score)
 
              rectangles[-1].append(labels[classId])
 
          else:
 
              print ('score = ', score)
 
 
 
def main():
 
    parser = argparse.ArgumentParser()
 
    parser.add_argument('--model', help='Path of the detection model.', required=True)
 
    parser.add_argument('--label', help='Path of the labels file.')
 
    parser.add_argument('--output', help='File path of the output image.')
 
    args = parser.parse_args()
 
 
 
    if ( args.output):
 
      output_file = args.output
 
    else:
 
      output_file = 'out.jpg'
 
 
 
    if ( args.label ):
 
      label_file = args.label
 
    else:
 
      label_file = None
 
 
 
    picam2 = Picamera2()
 
    preview = QtGlPreview(picam2)
 
    config = picam2.preview_configuration(main={"size": normalSize},
 
                                          lores={"size": lowresSize, "format": "YUV420"})
 
    picam2.configure(config)
 
 
 
    stride = picam2.stream_configuration("lores")["stride"]
 
    picam2.request_callback = DrawRectangles
 
 
 
    picam2.start()
 
 
 
    while True:
 
        buffer = picam2.capture_buffer("lores")
 
        grey = buffer[:stride*lowresSize[1]].reshape((lowresSize[1], stride))
 
        result = InferenceTensorFlow( grey, args.model, output_file, label_file )
 
 
 
if __name__ == '__main__':
 
  main()

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