How to set parameters of basler using python, _genicam.AccessException: Node is not writable

Question

Hi everyone Is this correct way to set the basler camera parameters using basler?

Is any other way to access camera after calling camera.stratGrabbing() function?

I am getting error like :

return _genicam.IInteger_SetValue(self, Value, Verify) _genicam.AccessException: Node is not writable. : AccessException thrown in node 'Height' while calling 'Height.SetValue()' (file 'integert.h', line 77)

import cv2
from pypylon import pylon

camera = pylon.InstantCamera(pylon.TlFactory.GetInstance().CreateFirstDevice())
converter = pylon.ImageFormatConverter()
camera.Open()
camera.CenterX=False
camera.CenterY=False

# demonstrate some feature access
new_width = camera.Width.GetValue() - camera.Width.GetInc()
if new_width >= camera.Width.GetMin():
    camera.Width.SetValue(new_width)

numberOfImagesToGrab = 100
camera.StartGrabbing()
camera.Open()
print("Max gain",camera.Gain.Max)
print("Min gain",camera.Gain.Min)
print("Max ExposureTime",camera.ExposureTime.Max)
print("Min ExposureTime",camera.ExposureTime.Min)
i=0
j=0
while camera.IsGrabbing():
    grabResult = camera.RetrieveResult(5000, pylon.TimeoutHandling_ThrowException)
    
    if grabResult.GrabSucceeded():
        i+=1
        j+=1
        if i==700:
            print(i)
            #camera.Open()
            camera.Height.SetValue( 200)
            camera.Width.SetValue( 300)
            
            camera.Gain=5
            camera.ExposureTime=8000
            i=0
        if j==500:
            #camera.Open()
            print(j)
            
            camera.Height.SetValue(1088)
            camera.Width.SetValue( 2048)
            
            camera.Gain=20
            camera.ExposureTime=8000
            j=0
        # Access the image data.
        
        print("AMAR :",camera.IsOpen())
        image = converter.Convert(grabResult)
        img = image.GetArray()
        cv2.imshow("image",img)
        cv2.waitKey(1)

grabResult.Release()
camera.Close()

Answer 1

# cam stop
cam.AcquisitionStop.Execute()
# grab unlock
cam.TLParamsLocked = False

cam.OffsetX = 0
cam.OffsetY = 0
cam.Width = cam.Width.Max // 4
cam.Height = cam.Height.Max // 4

# grab lock
cam.TLParamsLocked = True
# cam start
cam.AcquisitionStart.Execute()

With the lock it may help you

Answer 2

You cannot change camera's Width/Height parameters while camera is in grabbing state (after camera.StartGrabbing() ). Only RW parameters regarding AOI settings is OffsetX/OffsetY and some other model dependent ones (CenterX /CenterY / MirrorX / MirrorY) since they do not require reallocating internal memory buffers inside camera.

Put any Width/Height changes before grabbing loop, and after camera.Open().

From your code I presume you want to make some kind of dynamic parameter changes while camera is grabbing. Please consider Sequencer function of Basler ace cameras. In the nutshell - camera can change some parameters autonomically, frame by frame, without any user commands. However still, it won't help you in your Width/Height case.

Further reading below:
https://docs.baslerweb.com/sequencer-%28usb-cameras%29
https://docs.baslerweb.com/sequencer-(gige-cameras)