PiCameraValueError: Incorrect buffer length for resolution 1920x1080

问题

This is my code to detect circle/balls. I want to detect soccer ball from Pi camera. (soccer ball could be in any color.) I am having trouble with some PiCameraValueError. What is wrong with this code. I am using Raspberry Pi 2, Python2, and OpenCV.

from picamera.array import PiRGBArray
from picamera import PiCamera
import time
import cv2
import sys
import imutils
import cv2.cv as cv
# initialize the camera and grab a reference to the raw camera capture
camera = PiCamera()

rawCapture = PiRGBArray(camera)

# capture frames from the camera
for frame in camera.capture_continuous(rawCapture, format="bgr"):
    # grab the raw NumPy array representing the image, then initialize the timestamp
    # and occupied/unoccupied text
    image = frame.array
    img   = cv2.medianBlur(image, 5)
    imgg  = cv2.cvtColor(img, cv2.COLOR_RGB2GRAY)
    cimg  = cv2.cvtColor(imgg, cv2.COLOR_GRAY2BGR)
    imgg  = cv2.blur(imgg, (3,3))
            #imgg = cv2.dilate(imgg, np.ones((5, 5)))
            #imgg = cv2.GaussianBlur(imgg,(5,5),0)
    circles = cv2.HoughCircles(imgg, cv.CV_HOUGH_GRADIENT, 1, 20, param1=100, param2=40, minRadius=5, maxRadius=90)
    cv2.imshow("cimg", imgg)
    key = cv2.waitKey(1)
    if key & 0xFF == ord('q'):
        break
    if circles is None:
        continue

    print circles
            #circles = np.uint16(np.around(circles))
    for i in circles[0,:]:
        cv2.circle(cimg,(i[0],i[1]),i[2],(0,255,0),1) # draw the outer circle
                   #cv2.circle(cimg,(i[0],i[1]),2,(0,0,255),3) # draw the center of the circle
        cv2.imshow("Filtered", cimg)

cv2.destroyWindow("cimg")
cv2.destroyAllWindows()

回答1:

As explained here,

the PiCameraValueError is a secondary exception raised in response to the KeyboardInterrupt exception. This is quite normal and not a bug (it's more a consequence of how generic the output mechanism is in picamera), but it is difficult to detect and respond to in Python 2 (the usual method there would probably be to catch the PiCameraValueError as well in whatever loop your main script runs). Under Python 3, exception chaining is implemented so you could potentially look back through the stack of exceptions to find the KeyboardInterrupt one.

What you need to do is clear the stream between captures. The PiRGBArray docs cover doing this with truncate function.

Here is an example from, python face detection raspberry pi with picamera

import io
import time
import picamera
with picamera.PiCamera() as camera:
    stream = io.BytesIO()
    for foo in camera.capture_continuous(stream, format='jpeg'):
    # YOURS:  for frame in camera.capture_continuous(stream, format="bgr",  use_video_port=True):
        # Truncate the stream to the current position (in case
        # prior iterations output a longer image)
        stream.truncate()
        stream.seek(0)
        if process(stream):
            break

来源：https://stackoverflow.com/questions/40065328/picameravalueerror-incorrect-buffer-length-for-resolution-1920x1080

标签

python

OpenCV

raspberry-pi

detection

raspbian