如何解决如何使用使用 Vimba SDK 的 Allied Vision 相机在 tkinter 中预览流式图像?
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(),)
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