如何使用使用 Vimba SDK 的 Allied Vision 相机在 tkinter 中预览流式图像？

问题描述

我想使用 OpenCV 和相机 SDK VimbaPython 在 tkinter 框架内显示来自 Allied Vision 相机的图像。

初始化相机的唯一可能方法是使用 Python with 语句：

with Vimba.get_instance() as vimba:
    cams = vimba.get_all_cameras()
    with cams[0] as camera:
        camera.get_frame()
        # Convert frame to opencv image,then use Image.fromarray and ImageTk.PhotoImage to
        # display it on the tkinter GUI

到目前为止一切正常。但我不仅需要一个框架。相反，我需要不断获取帧并将它们显示在屏幕上，以便进行流式传输。我发现一种方法是从 tkinter Label 小部件调用 .after(delay,function) 方法。所以，在获得一帧之后，我想调用相同的函数来获取一个新的帧并再次显示它。代码看起来像这样：

with Vimba.get_instance() as vimba:
    cams = vimba.get_all_cameras()
    with cams[0] as camera:

        def show_frame():
            frame = camera.get_frame()
            frame = frame.as_opencv_image()
            im = Image.fromarray(frame)
            img = Image.PhotoImage(im)
            lblVideo.configure(image=img)   # this is the Tkinter Label Widget
            lblVideo.image = img

        show_frame()
        lblVideo.after(20,show_frame)

然后这会显示第一帧并停止，抛出一个错误，指出 Vimba 需要使用 with 语句进行初始化。我对 Python 了解不多，但看起来当我使用 .after() 方法调用函数时，它会以 with 语句结束。

我想知道是否可以在不结束 show_frame() 的情况下执行此 with 函数。此外，我无法每次都初始化相机，因为程序运行速度非常慢。谢谢

解决方法

我尝试读取 openCV 中的帧并将它们显示在 tkinter 标签中。我能够使用下面的代码做到这一点：

import tkinter as tk
import cv2
from PIL import ImageTk,Image

video_path = "SAMPLE/STORED_VIDEO/PATH"

root = tk.Tk()
base_img = Image.open("PATH/TO/DEFAULT/LABLE/IMAGE")
img_obj = ImageTk.PhotoImage(base_img)
lblVideo = tk.Label(root,image=img_obj)
lblVideo.pack()
cap = cv2.VideoCapture(video_path)

if cap.isOpened():
    def show_frame():
        _,frame = cap.read()
        im = Image.fromarray(frame)
        img = ImageTk.PhotoImage(im)
        lblVideo.configure(image=img)
        lblVideo.image = img
        lblVideo.after(1,show_frame)  # Need to create callback here   
    show_frame()
root.mainloop()

虽然这不包含 with 语句，但您可以尝试替换 after() 函数本身内部的 show_frame 回调。

您需要使用线程来运行捕获代码并传递通过 queue 读取的帧。然后主 tkinter 应用程序读取 queue 并使用 .after() 定期显示帧。

以下是基于您发布的代码的示例：

import threading
from queue import SimpleQueue
import tkinter as tk
from PIL import Image,ImageTk
from vimba import Vimba

def camera_streaming(queue):
    global is_streaming
    is_streaming = True
    print("streaming started")
    with Vimba.get_instance() as vimba:
        with vimba.get_all_cameras()[0] as camera:
            while is_streaming:
                frame = camera.get_frame()
                frame = frame.as_opencv_image()
                im = Image.fromarray(frame)
                img = ImageTk.PhotoImage(im)
                queue.put(img) # put the capture image into queue
    print("streaming stopped")

def start_streaming():
    start_btn["state"] = "disabled" # disable start button to avoid running the threaded task more than once
    stop_btn["state"] = "normal"    # enable stop button to allow user to stop the threaded task
    show_streaming()
    threading.Thread(target=camera_streaming,args=(queue,),daemon=True).start()

def stop_streaming():
    global is_streaming,after_id
    is_streaming = False  # terminate the streaming thread
    if after_id:
        lblVideo.after_cancel(after_id) # cancel the showing task
        after_id = None
    stop_btn["state"] = "disabled" # disable stop button
    start_btn["state"] = "normal"  # enable start button

# periodical task to show frames in queue
def show_streaming():
    global after_id
    if not queue.empty():
        image = queue.get()
        lblVideo.config(image=image)
        lblVideo.image = image
    after_id = lblVideo.after(20,show_streaming)

queue = SimpleQueue() # queue for video frames
after_id = None

root = tk.Tk()

lblVideo = tk.Label(root,image=tk.PhotoImage(),width=640,height=480)
lblVideo.grid(row=0,column=0,columnspan=2)

start_btn = tk.Button(root,text="Start",width=10,command=start_streaming)
start_btn.grid(row=1,column=0)

stop_btn = tk.Button(root,text="Stop",command=stop_streaming,state="disabled")
stop_btn.grid(row=1,column=1)

root.mainloop()

注意我没有安装摄像头和SDK，上面的代码可能对你不起作用。我只是演示了如何使用线程、队列和.after()。

下面是一个测试 vimba 模块（另存为 vimba.py），我用来使用 VimbaPython 和网络摄像头模拟 OpenCV 模块：

import cv2

class Frame:
    def __init__(self,frame):
        self.frame = frame

    def as_opencv_image(self):
        return self.frame

class Camera:
    def __init__(self,cam_id=0):
        self.cap = cv2.VideoCapture(cam_id,cv2.CAP_DSHOW)

    def __enter__(self):
        return self
    
    def __exit__(self,*args):
        self.cap.release()
        return self

    def get_frame(self):
        ret,frame = self.cap.read()
        if ret:
            return Frame(frame)

class Vimba:
    _instance = None
    
    @classmethod
    def get_instance(self):
        if self._instance is None:
            self._instance = Vimba()
        return self._instance

    def __enter__(self):
        return self

    def __exit__(self,*args):
        return self

    def get_all_cameras(self):
        return (Camera(),)

camera camera python stream tkinter video video