I'm having a difficult time figuring out how to send and receive an image (and display it, not save it) via UDP socket or named pipe (fifo) on linux.
With UDP sockets the problem I have is the file size exceeds the max buffer size. Conceptually I could iterate over a bytearray of the image in buffer-size chunks, but I'm not sure how to implement this, or how to reconstruct the image on the other side.
With named pipes, below is my code.
p1.py:
fifo_name = "fifoTest"
def Test():
img = cv2.imread("Lenna.png")
data = bytearray(img)
try:
os.mkfifo(fifo_name)
print("made fifo")
except FileExistsError:
print("fifo exists!")
with open(fifo_name, "wb", os.O_NONBLOCK) as f:
f.write(data)
f.close()
print("done!")
Some issues with p1 is that I can't seem to figure out when the writing to the pipe has finished, and often time no matter what happens on the other pipe this gives a BrokenPipeError
p2.py:
import os
import io
from PIL import Image
import cv2
pipe = os.open("fifoTest", os.O_RDONLY, os.O_NONBLOCK)
# img is 117966bytes as given by shell command wc -c < Lenna.png
imgBytes = os.read(pipe, 117966)
#img = Image.open(io.BytesIO(imgBytes))
print(imgBytes)
print(len(imgBytes))
#cv2.imshow("img", img)
input("there?")
With p2 and the commented lines, I have no problems. After input captures my keypress, I get no errors, but as mentioned about p1 errors with broken pipe. When img = Image.open(io.BytesIO(imgBytes)) is uncommented, I get
img = Image.open(io.BytesIO(imgBytes))
File "/usr/local/lib/python3.5/dist-packages/PIL/Image.py", line 2585, in open
% (filename if filename else fp))
OSError: cannot identify image file <_io.BytesIO object at 0x7f21b84b0a98>
I feel like this shouldnt be a hard problem, this is a really basic operation. I need this to happen at about 10fps (which is why I'm not looking at other options). I have also gotten resource temporarily unavailable error a few times, but I think the os.O_NONBLOCK flag fixed that.
Things that I have already looked at (some were helpful, but I need to display an image once its received):
Sending image over sockets (ONLY) in Python, image can not be open
Send image using socket programming Python
